1 .Growth Analysis of Bartfy (Cv. Zephyr) Infected With

.GROWTH ANALYSIS OF BARTFY (CV. ZEPHYR) INFECTED WITH ERYSIPHE GRAMINIS

- by

Malcolm Edwin Finney B.Sc.

A thesis presented in part fulfilment of the requirements for the Degree of Doctor of Philosophy in the Faculty of Science of the University of London.

Department of Botany, Imperial College of Science and Technology, Silwood Park, Ascot, Berkshire. October 1973. ABSTRACT

In a greenhouse experiment in which mildew was allowed to develop only during particular stages of growth, yields were most affected by mildew at stem extension. Infection during tillering also decreased yield but infection at heading had little effect.

In the field, infection with Ej:ysjiy11gxaminis DC; on spring barley cv. Zephyr was found to cause yield reductions of 15-20% due to the premature initiation of senescence in infected leaves.

In a field situation take-all caused by Gaeumannomyces mamiala yielded 30% less than control by reduction of the number of fertile tillers, while plants infected with both mildew and take-all yielded only 32% less than control. Take-all was found to be more severe in this case, while mildew levels were reduced.

Ethirimol used to control mildew in the field experiments was found to cause an increase in leaf area on plants grown free from mildew in a "spore free cabinet". Also, it prolonged the maintenance of green leaf tissue in mildew infected plants and led to a consequent increase in shoot dry weight above that of untreated and disease free plants. ACKNOWLEDGEMENTS

I wish to thank my Supervisor Dr.B.E.J. Wheeler for his constant help and guidance throughout this work and his constructive criticism of this manuscript.

I should also like to thank Dr.D.H. Brooks formerly of I.C.I. Plant Protection Ltd., (Jealott's Hill) for his help and various members of the staff of Plant Protection Ltd., for their co-operation and assistance especially in setting up field trials.

I must thank the staff of Imperial College Field Station, Silwood Park, in particular those of the Botany Department, Mrs.P. Tyler and Miss C. Davies for recording and Mr.E.E. Green for technical advice.

Sincere thanks go to Mr.J.M. Stringer Silwood Park's Superintendent of Horticulture for his co-operation and the assistance of his team of gardeners in setting up and harvesting field trials.

I would also like to thank Professor S.D. Garrett for supplying cultures of Gaeumannomvces graminis.

Finally I would like to thank my mother for typing this manuscript and also my wife for typing the tables but above all I would like to thank her for her support during this work.

This work was done while under the tenure of an S.R.C. CAPS Award in conjunction with I.C.I. Plant Protection Ltd., (Jealott's Hill) the receipt of which I gratefully acknowledge. -5-

CONTENTS

Page No.

TITLE PAGE 1

ABSTRACT 2

ACKNOWLEDGEMENTS

CONTENTS 5

INTRODUCTION 6

REVIEW OF LITERATURE 8

MATERIALS AND METHODS 13

EXPERIMENTAL 25

DISCUSSION 109

SUMMARY 119

REFERENCES 121

APPENDIX I 127

APPENDIX II 150

APPENDIX III 226 INTRODUCTION

Recent surveys have shown (James, 1969) that powdery mildew caused by Erysiphe graminis DC. is the most important disease of spring barley in England, causing losses in yield averaging 10%. These effects of mildew attack on yield have been well documented, (Last, 1955, 1962; Large and Doling, 1962), but in spite of the importance of the disease, comparatively little work has been done to measure its effect on the pattern of growth of the crop.

Glasshouse experiments, open to criticism in comparison with the field situation, have shown that mildew decreases the number of tillers producing ears and stunts the shoot and root systems (Last, 1962; Paulech, 1969). The stunting of the root system is of particular interest, especially in plants that may be subject to take-all caused by Gaeumannomyces graminis (Last, 1962). However, these experiments have done little to measure the effects that mildew may have at a particular phase of growth, while this is of major importance to the grower if he is to control_ the disease successfully and above all economically.

The development of the systemic fungicide ethirimol (Bebbington, Brooks, Geoghegan and Snell 1969) -7_

by Plant Protection Ltd.,(Imperial Chemical Industries) has considerably altered control practices for this disease and also has provided research workers with a means of limiting mildew infection to particular growth stages.

In the present studies ethirimol has been used in this way in experiments in the greenhouse and also in its more usual application as a seed-dressing in field experiments. In these situations the effect of the chemical on the plant is confounded with its ability to control mildew. To overcome this, spore-free cabinets were developed which allowed a comparative study of plants in a mildew-free environment. -8-

REVIEW OF LITERATURE

There is now a vast literature concerning powdery mildew on cereals but this account will be limited to a consideration of the ways in which Erysiphergamj_nis DC. reduces the yield of a crop, especially of barley.

To do this, one should first consider which organs of the plant contribute most to the filling of the grain. Current opinion is that the flag leaf and its sheath and the photosynthetic tissue of the ear itself are most important. Archbold (1942)1 studied this in detail using methods of defoliation and shading to ascertain the part played by various organs of the plant in contributing to the final yield. He found that defoliation of the plant alone, reduced the number of ears reaching maturity but not their size or the grain size. Under the conditions of the experiment therefore, leaves made no contribution to grain filling, but were of paramount importance in ear formation. Early removal of the flag- leaf and sheath reduced grain size, but later removal had no effect.

Shading the ears reduced the size of the ear, but did not affect the number produced and as stem sugars suffered only a small reduction, the shaded ears were only able to utilise a small part of the material which would otherwise have appeared as sugar in the stems. -9-

He therefore concluded that the carbohydrates of the ear were entirely supplied by dirOctly assimilated material, translocated immediately from the various organs. The extent to which each contributes, calculated from observation on samples collected 19 weeks after sowing was : Leaves 15% Flag-leaf and sheath 15% Stem and other sheaths 40% Ears 30%

Watson, Thorne and French (1958) support this work, in that in their experiments the differences in yield between three barley cultivars could be attributed to photosynthesis occurring in parts of the plant other than the leaves. The Leaf Area Indices of the three varieties and their Net Assimilation rates were found to be approximately the same before ear emergence, and it was concluded that the sources of final yield could be partitioned in this manner : 26% Ear including 10% from Awns. 59% from Flag leaf and sheath. 15% from parts of the shoot below Flag leaf.

Porter,Pal and Martin (1950), also showed that the ear of barley contributes approximately 30% to the final yield, using radio-carbon studies. However, there is still conjecture as to the source of the other 70%. Current opinion would probably support the idea of Watson, Thorne and French (1958) in that approximately 60% comes from the Flag leaf and sheath. -10-

Welbank, French and Witts (1966), showed that differences in yield between wheat varieties could in part be attributed to differences in their Leaf Area Durations, (the period for which leaves remain green after ear emergence). This fact therefore must also be borne in mind when considering an analysis of the final yield from barley.

Thorne (1959) decided that for growth analysis determinations the photosynthetic area of cereal plants should be considered as that of one surface of the leaf laminae plus the outer surface of the combined leaf sheaths.

Exasiahl graminis DC. can infect any of these photosynethic surfaces though it tends to attack the lower leaves to a greater extent. E. graminis lives superficially sending only haustoria into epidermal cells of aerial structures but it can cause appreciable crop losses. Last (1955) showed decreases in yield of up to 22% with severe infection. Here, the basic assumption is that yields are decreased because mildew kills the leaf and so less assimilate passes to the developing grain. There is no doubt that the development of E. graminis on the leaf does affect photosynthesis as shown by Millerd and Scott (1956), who also showed that there was an increase in the rate of respiration. This is supported by work by Scott and Smillie (1963) who linked this with a reduction in the capacity for barley to photoreduce NADP-1-. However, other experiments suggest that decreases in photosynthesis cannot simply be attributed to a loss of leaf area. Last (1963) showed that when lass than 30% of a leaf was inoculated with mildew, decreases were equivalent to area losses greater than those inoculated, while when more than 30% was inoculated the photosynthetic losses were equivalent to area losses less than those inoculated. He also concluded that though the relative effects on respiration and photosynthesis were of the same order, the absolute effects on photosynthesis were greater than those on respiration.

There are also effects of mildew which can alter the early development of the plant. Last (1962) showed that heavy infection with mildew caused a loss in leaf area and fewer shoots which formed ears, and caused a reduction in the Net Assimilation Rate in infected plants. Also, these early infections affect the roots more than:the shoots so that the dry-weight ratio of root/total plant is decreased. Brooks-(1972) supports this and notes that spring barley which is not severely infected in its early stages of growth does not appear stunted and yield loss is attributable only to a decrease in the size of grain produced. Both Last and Brooks noted that this reduction in the root system may be a far more important loss to the plant than that of the leaf area. This is of especial interest where plants may also be subject to attack by Gaeumannomyces Emaninig. -12-

It was on the basis of the preceding information that Large and Doling (1962) attempted to relate final yield losses due to mildew to its severity on the upper leaves. They devised a field key for mildew assessment which called for the estimation of mildew on the upper four leaf-blades only. The key takes into account the amount of mildew which may be present and the degree of yellowing caused by this mildew. It also corrects for the relative importance, as regards yield, of the various leaves assessed. After several years trials it was found that the percentage loss of grain yield due to mildew was about 2f times the square root of the percentage mildew assessment made after the completion of heading and before the onset of ripening.

Despite the evidence from experiments in growth cabinets which suggest that the upper leaves contribute most to growth and to the assocation of mildew on these leaves with final yields by Large and Doling, the basic question remains - "How much do early attacks of mildew in the field affect yield?" This question has been highlighted in trials with systemic fungicides where in some instances treatment has apparently led to yield increases greater than expected from a consideration of mildew levels on the upper leaves of plants from untreated plots. -13-

MATERIALS AND METHODS.

(1) INITIAL GREENHOUSE EXPERIMENTS

Experimental plants

Seed of the barley cultivar Zephyr was treated with 'Ceresan' (0.2g/100g seed) and then sown at a depth of 11 in. (4cm) in 10 in. (25 cm) pots containing John Innes No. 2 compost. These were kept on a sand bench with automatic watering in a greenhouse, beneath six 400 watt mercury vapour lamps which gave a light intensity of c 6,500 lumens/m2 at bench level for 16 h per day. When the seedlings emerged they were thinned to six per pot.

Mildew inoculum

Barley plants infected with Erysiphe graminis were obtained from Plant Protection Ltd. (Jealott's Hill). These were shaken over the experimental plants so that a relatively uniform deposit of conidia alighted on them.

Chemicals

Mildew control was achieved by spraying plants with ethirimol J.F. 2573 (20% w/v ethirimol, as its hydrochloride solution) at a rate of 75 p.p.m. (a.i.) to just below run-off. This ensured that no spray collected in the leaf axils and thus became systemic within the plant. Spray was delivered by means of a Devilbiss paint spray type EGA operated by air at 15 lbs/in2 pressure, from an Edwards Vacuum Pump (RB4). This arrangement gave a very easily controlled, extremely fine droplet spray, allowing excellent coverage without run-off.

(2) FIELD EXPERIMENTS

Chemicals

Zephyr barley seed pre-dressed with 'Ceresan' was sown at a rate of approximately 11 cwts per acre (190 Kg/ha).

Where necessary seed was also treated with ethirimol at the rate of 0.8% w/w a.i. on the seed.

In some cases experimental design necessitated that mildew should be controlled using sprays. This was done using a Kestrel Knapsack Sprayer (Polypak, Kestrel Sprayers Ltd.) fitted with a cone-jet type nozzle delivering 5 ml ethirimol col form (25% w/v a.i.) in 1 litres of water to each 6ft x 20ft (c 2m x 7m) plot at a pressure of 20 - 30 lbs/in2. Some degree of droughting was applied where required by means of plastic channels placed between the rows of barley. The channels were constructed from strips of 'Claritex' (wire reinforced plastic sheeting - Transatlantic Plastics Ltd.,) Bin wide and 12f t long (20 x 360 cm) bent into a 'V'. These strips (9 per plot) were attached at each end to wooden stakes (lin x lin x 10in 2.5 x 2.5 x 25 cm) driven into the ground, one end being at ground level, the other 5 or more cm above, creating a 'fall' over the length of the plot. Gaps between adjacent strips of 'Claritex' allowed the plants to grow through, but were small enough to ensure that most of the plot was covered.(Figs.l and 2). By raising the channels slightly above the soil surface the 'mulching' effect of the sheeting was minimized.

The effectiveness of this method of droughting was assessed by weekly soil samples. Several 12 in long soil cores were taken at random from within and between the rows of barley both under drought and control, throughout the experimental area. These cores were then divided into upper and lower 6in sections, which were weighed before and after drying for 2-F h at 70°C. From this information the percentage water content could be calculated, both in droughted and control plots. Fig.1 Drought channelling between rows of barley

Fig.2 Extension of channelling beyond end of plot Take -all

In an attempt to induce take-all, grain artificially infested with Gaeumannomyces graminis was sown alongside healthy grain in some plots by discharging it at a comparable seeding rate from the fertilizer box of a combined seed drill. The infested grain was produced as follows:-

Distilled water was added to grain at the rate of 30m1/100g and this was then autoclaved at 120°C for 1 h in suitable containers. After cooling these were inoculated with mycelial plugs cut aseptically from cultures of G. graminis on 24 malt agar and then incubated at 23°C. The cultures were shaken regularly to ensure an even distribution of the fungus through • the grain. Then, after 6 weeks, the grain was removed and dried for 48 h on a flat surface.

(3) CHLOROPHYLL LEVELS IN HEALTHY AND INFECTED:PLANTS

Growth of plants

Plants for these experiments were grown singly in 3in (8 cm) pots of peat/sand mixture from seed sown at a depth of liin (4 cm). These pots were placed within specially constructed cabinets (see over) on an automatic watering bench, within a greenhouse supplied with artificial lighting. This consisted of twenty-seven 80 watt Daylight fluorescent tubes(Atlas) -18-

suspended 15 cm above the cabinets and maintained on a 16 h photoperiod.

Spore-free cabinets

Special cabinets (Figs 3, 4 & 5) were constructed so that barley plants could be grown to maturity, free of bildew, without the use of chemical. The framework of these cabinets was of 'Handy Angle' (Dexion Ltd.) witn the fixing nuts set on the outside to leave a relatively smooth internal section. The top and three sides were formed of transparent plastic sheeting (0.030in Transatlantic Plastics. Ltd) which was bolted to the framework and then sealed to it with metal casemmt putty. Joins in the plastic sheeting were sealed with Transparent Lasso waterproof tape (Sellotape Products Ltd.).

On the fourth side two extra metal uprights spaced lft from each end, provided (with the top and bottom members of the frame) the support for a 'hood' of polyethylene (500 gauge) which allowed access to the cabinet. The spaces between these and the corner uprights were enclosed with plastic sheeting. Air was blown into the cabinet through a Sterile Air Filter size 1, grade D at the rate of 25 c.f.m. by a tangential fan. The fan and filter were housed ia a single unit (Foramaflow Ltd.), which was fixed to one side of the cabinet to allow removal, if necessary, without disturbing the experiments in progress within the rn 13N 141 VO mx) m

1 -20-

Fig.4 Polythene hood arrangement on Spore-Free Cabinet

Fig.5 Fan and filter unit on Spore-Free Cabinet -21-

cabinet.

The base of the cabinet was embedded in the sand bench to allow automatic watering of potted plants placed within it.

Two cabinets were used in the experiments, one from which mildew was excluded and the other in which mildew was allowed to develop. Conditions were therfore similar except for the presence or absence of the disease.

Extraction of chlorophyll

Chlorophyll was extracted by a method based on that of Bruinsma (1963).

In the first experiment, one or two leaves (depending on size and bulk) were cut into lcm sections and placed in the micro-attachment of a 'Sorvall Omni- Mixer', where they were ground for 12 min at half speed with 5 ml of acetone. The plant tissue was vacuum- filtered through a 17 x 5 sintered glass funnel using successive washes of fresh acetone, until no chlorophyll remained in the filter. The volume of the filtrate was then measured, corrected to 90 acetone by the addition of distilled water and the final volume noted. After thorough mixing the absorbancy of the extracts was measured in turn at 641mA and 663m. (Mackinney, 1541) using a Beckmann DB Spectrophotometer. -22-

The amounts of chlorophylls a and b were calculated from:- Arnon (191+9)

Total chlorophyll (mg/1) = 20.2D645 + 8.02D663 = 2781)652

Chlorophyll a (mg/1) = 12.7D663 - 2.69D645

Chlorophyll b (mg/1) = 22.91)645 - 4.681)663

In later experiments plant tissue was extracted with methanol and the procedure simplified. In these, the whole plant was cut into 1 cm sections, placed in the 250 ml capacity container of the 'Sorvall Omni Mixer',. and ground in a quantity of methanol and for a period which depended on the bulk of plant material present.

Up to 3 leaves, 15 ml methanol 2 min grinding Up to 6 leaves, 20 ml methanol 2 min grinding More than 6 leaves, 25 ml methanol 3 min grinding

This ensured the complete maceration of the tissue and release of chlorophyll for the cells.

The macerate was then filtered as before, washing through with methanol until no chlorophyll remained in the filter. The residual plant debris was scrapped from the filter, placed in a specimen tube, dried for 21+ h at 70°C and then weighed. The filtrate was made up to a known volume with methanol, thoroughly mixed, and its absorbancy measured at -23-

65015u and 6651444

The amount of the two chlorophylls was calculated from the equations: Holden (1965)

Total chlorophyll (mg/1) 25.5D650 + 4.0D665

Chlorophyll a (mg/1) = 16.5D665 - 8.3D650

Chlorophyll b (mg/1) = 33.8D650 12.5D665

(4) MEASUREMENTS

Leaf area

Leaf area was calculated from measurements of the length (1) and maximum breadth (b) as: 0.8065 lb The factor, 0.90651 was derived from the regression of lb on actual leaf area in a pilot experiment with Zephyr barley in which actual leaf area was estimated by placing them on amino-positive blue print paper, and then by measuring them both with a planimeter and from tracings on graph paper.

Disease assessments

The percentage mildew on both leaf surfaces was estimated from the standard diagram produced by the Ministry of Agriculture. A value for the overall, percentage mildew per Plant was derived by taking, for each leaf, the mean of the above figures,' multiplying by twice the leaf surface area (i.e. 2 x 0.9065 lb, to account for both surfaces), summing the products and expressing these as a percentage of the total green leaf surface area. The latter was calculated from separate assessments of senescent tissue on individual leaves. -25-

EXPERIMENTAL

(A) An experiment to determine the effect of mildew at different growth stages was first set up in November 1970. This had to be abandoned because the plants, grown in soil from the Walled Garden at .Silwood, showed signs of calcium deficiency. Also it proved difficult to infect those leaves which were produced with mildew although there were plenty of viable conidia of EL._graminis present. The experiment is discussed fully in Appendix (I).

A second experiment was set up in February 1971 with essentially similar aims. These were to study the effect of mildew during one or more of three distinct phases in the growth of the plant, based as follows on the Feekes scale (Large, 1954) : Growth stage Infection Leaf,: No. Period Tillering 1- 5 A 1- 5 Stem Extension 6- 9 B 6 - 9 Grain Filling 10 - 11 C 9

In all there were eight treatments in which plants were allowed to become infected with mildew during the following growth periods : Treatment Infection Period 1 A 2 A+B 3 A+B+C 4 A+C 5 -26-

Treatment Infection Period 6 B+C 7 8 Nil

Otherwise plants were kept free of mildew by spraying them with ethirimol as described (p.13 and below).

Pots (25 cm diam) of John Innes compost No.2 were sown on 9 February 1971 and arranged in eight randomized blocks as indicated in Fig. 6 with provision for additional pots of barley (I) which, when inoculated would serve subsequently as sources of inoculum throughout the experiment.

The first spray of ethirimol was applied on 26 February, 17 days after sowing, to plants in treatments 5, 6, 7 and 8 i.e. treatments requiring no mildew in growth period A. Two hours later all plants in the experiment were dusted with conidia of E. graminis. There were further applications of ethirimol to meet the requirements of the experiment as follows :

Date Days after Applied to Sowin Treatment No. 5 March 23 5, 6, 7, and 8 16 March 34 1, 4, 7, and 8 25 March 43 1, 4, 7, and 8 2 April 51 1, 4, 7, and 8 20 April 69 1, 2, 5, and 8 -27- FIG 6

EXPERIMENTAL LAYOUT

BLOCKS BLOC1

~~8000000 YI. IT (2~)(vffi0000 (0s000 CD 0000800 - 1m IIT 0000000 00080 CD 000CDffi0ffi 000ffi 50) 4 00 r 00~~

~~TREATMENT INFECTION PERIOD 1 A 2 A+B 3 A +- B -l-C 4 A+C 5 B 6 B +- C 7 C 8 NIL I INOCULUM -28-~~

To allow a continuous record of growth, measurements were carried out on the main shoot of one marked plant per pot at approximately seven day intervals from 16 days after sowing (25 February) till ear emergence (7 April).

~~The area, degree of mildew infection and senescence were recorded for each leaf' on the plant.~~

On (1 June) 110 days after sowing, the dry weight of the ears and shoots of marked plants and also that of the ears of other plants were determined. At the same time the fertile tillers were counted on each marked plant.

Results Table T shows the progression of mildew infection throughout the experiment, and the general effectiveness of ethirimol in the control and erradication of the fungus. The high figures are probably due to E. graminis infecting a previously healthy plant.

Figs. 7 and 8 (Appendix tables 23 and 24) show the marked reduction in final yield due to mildew infection during stem extension (period B) infection during grain filling (period C) had little or no affect. The changes in shoot dry weight are not so marked Fig.9 (Appendix table 25). -29-

~~TABLE 1~~

~~MILDEW PER PLANT DURING TILLERING AND STEM EXTENSION IN RELATION TO INFECTION PERIOD.~~

~~INFECTION DAYS AFTER SOWING PERIOD 30 37 47 57~~

~~A 3.31 2.71 0.70 0.37~~

~~A+B 3.20 5.30 3.69 ' 3.82~~

~~A+B+C 2.93 3.32 4.18 3.93~~

~~A+C 2.98 3.15 . 0.79 0.51~~

~~B 0.41 4.48 7.28 3.63 B+C 0.15 2.64 6.39 2.27~~

~~C 0.05 0.75 0.69 0.18~~

~~NIL 0.15 1.05 0.55 0.14~~

~~Infection Period Infection Period~~

~~A -30-~~

~~FIG 7~~

~~DRY WEIGHT, EARS FROM MARKED PLANTS~~

~~DPY WT.~~

~~G. L.S.D. p 005~~

~~NIL A B C A+. A +C B+C Ai-BC~~

~~INFECTION PERIODS~~

~~FIG 8~~

~~DRY WEIGHT, EARS FROM OTHER PLANTS~~

~~DRY 30 WT. G. 20~~

~~L.S.D. 5 10 p~~

~~NIL A B C A+E5 A+C B+C A+B4C~~

~~INFECTION PERIODS -31-~~

~~FIG 9~~

~~DRY WEIGHT OF MARKED PLANTS~~

~~■••■•■••■•••~~

~~6 DRY L.S.D. WT. p 0.05 4 G.~~

~~NIL A B C A+B A+C B+C A+B.0~~

INFECTION PERIODS Mildew infection had no significant effect on the area of individual leaves produced (Table 2 Appendix table 26) and thus also no effect on the total amount of leaf area present at one time (Table 3 Appendix table 27). However, there were differences in the green leaf area of the plants resulting from the treatments. Thus by (8 April) 57 days after sowing, those plants which were infected with mildew during stem extension (growth period B) had significantly less green tissue than the others (Table 4 Appendix table 28) because the leaves senesced more rapidly (Table 5).

The results demonstrate a clear effect of mildew at stem extension and suggest, too, that mildew during tillering may also depress yield. Possibly the latter results from its effects on root development (Last, 1962 : Brooks, 1972). TABLE a'

~~MEAN LEAF SIZE (CM2) IN RELATION TO MILDEW INFECTION (Eight replicates)~~

~~Infection Leaf Number Period 1 2 3 4 5 6 7~~

A 5.38 8.63 1'.94 25.14 33.28 37.42 42.29 A+B 6.51 10.02 16.03 26.07 35.66 38.21 40.49 A+B+C 6.36 9.99 16.93 23.91 33.85 36.42 40.10 A+C 6.13 9.28 16.79 26.75 34.96 37.84 41.47 B 5.34 9.14 16.50 26.02 35.36 37.17 41.72 B+C 6.41 10.50 17.01 26.95 37.12 41.37 44.50 C 7.09 10.82 17.94 27.85 36.10 39.55 43.09 Nil 6.51 9.82 14.96 27.09 33.29 38.08 42.14

~~L.S.D. 0.98 2.05 2.78 2.76 3.16 3.62 4.72 p=0.05~~

~~Formed in Period Formed in Period A TABLE~~

~~MEAN TOTAL LEAF AREA PRODUCED (CM2) IN RELATION TO MILDEW INFECTION (Eight replicates)~~

~~Infection Days after sowing~~

Period 16 23 3o 37 47 57 uo 47" 1 A 7.57 28.18 55.o8 116.73 162.33 227.99 A+B 11.46 33.97 59.94 123.67 174.30 248.12 A+B+C 9.67 33.28 57.19 122.36 167.69 247.2o A+C 8.45 30.44 59.46 116.76 173.73 248.16 B 9.33 32.43 57.2o 125.72 171.49 244.29 B+C 11.33 33.92 6o.88 139.37 183.86 236.06 C 9.46 35.85 63.69 134.41 192.43 245.43 Nil 6.51 30.68 54.83 111.72 167.58 245.05

~~L.S.D. 33.70 p=0.05 Infection Period A Infection Period B TABLE 4 MEAN GREEN LEAF AREA (CM2) IN RELATION TO MILDEW INFECTION (Eight replicates)~~

Infection Days after sowing Period 16 23 3o 37 47 57 1 A 7.57 28.13 55.08 99.13 138.96 175.45 w A+B 11.46 33.87 59.94 99.53 116.96 118.53 1 A+B+C 9.67 33.28 57.19 98.89 108.49 126.17 A+C 8.45 30.44 59.46 99.65 142.58 131.69 B 9.33 32.43 57.20 125.30 113.88 114.71 B+C 11.33 33.92 60.88 138.19 137.63 87.42 c 9.46 35.85 63.69 134.10 16o.4o 178.42 Nil 6.51 30.68 54.83 111.16 159.74 190.14

~~L.S.D. 44.1+2 p=0.05 Infection Period A Infection Period B -36-~~

~~TABLE 5~~

~~% SENESCENCE PER PLANT DURING TILLERING AND STEM EXTENSION IN RELATION TO MILDEW INFECTION PERIOD.~~

~~INFECTION DAYS AFTER SOWING PERIOD 3o 37 47 57~~

~~A - 15.08 14.66 23.04~~

~~A+B . 19.52 32.90 52.23~~

~~A+B+C - 19.18 35.3o 48.96~~

~~A+C - 15.51 17.93 26.78~~

~~B - 0.34 33.60 53.04~~

~~B+C - 0.84 25.14 63.00 c - 0.23 12.08 27.30~~

~~NIL - 0.50 5.28 26.49~~

~~Infection Period Infection Period~~

~~A -37-~~

~~B INTERACTIONS OF POWDERY MILDEW, TAKE ALL AND DROUGHT.~~

~~(i) Field Experiment 1971~~

Although mildew was controlled in the greenhouse experiment by spraying plants with ethirimol, commercially this material is usually applied to the seed to control the disease in crops. In this situation control relies on the gradual absorption of ethirimol by the developing roots and factors which affect root growth are thus likely to affect the efficiency of mildew control. In this connection the presence of root-infecting fungi such as GLaglaIan.nosausgraminis which causes the well known disease take-all, is of special interest. So, too, are periods of drought which are likely to affect the rate at which the roots absorb ethirimol. The 1971 field experiment was designed specifically to study the interaction of these factors on mildew development.

The experiment was designed with four blocks of four main plots (drought treatments) each split into four sub plots (disease treatments) as follows : G.S. Main plots No drought Do Drought during tillering D1 1-5 Drought during stem extension D2 6-9 Drought during grain filling D3 10-11 -38-

~~Sub-plots Control 0 Mildew only Take-all only Take-all and mildew T & M~~

~~The complete layout is shown in Fig.10.~~

~~The experiment was laid down on 19 April at Jealott's Hill Research Station (Plat Protection Ltd) on a site with a good clay/loam soil, but in parts rather poorly drained.~~

Sub-plots for the take-all treatment were infected with G. graminis by the method detailed on page 17 . Mildew sub-plots relied on natural infection and sub-plots requiring no mildew were sown with ethirimol-dressed seed.

Leaf area, degree of mildew infection, amount of senescence, height and shoot dry weight were determined on the main stems of ten plants per sub-plot fortnightly from 25 May to 6 July (i.e. from 36 to 78 days after sowing). The dry weight of shoots and ears only were measured 93 and 108 days after sowing. All leaves were dead by this time. In all instances plants were dried for 3 or 4 days at 70°C before weighing.

~~Take-all was assessed on 4 August, 108 days after sowing, on three one foot row lengths. Roots were washed and graded (0) no take-all present (1) slight~~

~~Ifl ris ill lir III ill III 111 1 2 3 4 5 6 7 13 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 2728 29 30 31 32 .~~

~~DO D2 DI D3 D3 Di D2 DO~~

I 1 - I T I I T 1 i -ri I I IT) till- {III Tfli I I I T & & & & & & & & MI T I o lm O I T I MI M MI MI O I T O'M'M'T OI MI T I M 01 T / MI M MI MI T I O 01 T I MI M , , . II! L I I I J I II I I I I III III X3 d A 4-24=—÷ BLOCK I BLOCK IL N183

~~20' "WiN3~~

~~It! III III III ill II 1 1 1 I 1 I t '33 34 35 36 37 38 3940 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 6364~~

~~DI D3 D2 DO D3 DI D2 DO~~

~~T T T T T T T I I I I I I I I I 1 il 1 I 1 lig ell iiT 1 & & & & , , &, , , & M'M' TI 0 MI TIOIM OIMIMI T 01 MI TI M TIM' M'O M' TI MI 0 MI T I O I M M'OIMIT I I I I I I III III I I I, IlL It! III~~

~~BLOCK BE BLOCK IV_ take-all, 25% roots affected (2) severe take-all 50% roots affected, and a take-all index recorded for each plot~~

~~gsm211gulta 100 X No. of plants assessed 2~~

~~Results were thus related to the number of plants sampled.~~

Drought channelling (see Materials and Methods page 15 ), was placed on D1 plots on 11 May, 22 days after sowing, and was moved to D2 plots on 7 June, 49 days after sowing, and to D3 plots on 1 July, 73 days after sowing. The channelling was removed altogether on 4 August some 108 days after sowing.

~~The interelation of the various samples and treatments is shown in Fig.11.~~

Plots were harvested on 19 August, 123 days after sowing, using a sickle and the grain from each plot was separated in a stationary, tractor driven Dania thresher (Dronningborg Maskinfabrik Denmark), allowing a constant elapsed time between plots through the machine. The grain was bagged, weighed and a sample assessed for moisture content, by drying for 4 days at 70°C. Yields quoted are corrected for moisture content. FIG II SAMPLING DATES AND TREATMENT PERIODS FIELD J971·

~~SAMPLES I +'" ~ I 2 :3 4 5 6~~

~~19 APRIL 19 AUGUST o 20 40 60 80 (00 (20~~

~~DAYS AFTER sow I NG~~

~~A A ~ 0~~

~~01 D2 D3~~

~~GROWTH STAGES 1-5 6- 9 10 - )) -42-~~

Weighed samples of grain were then passed through a sieving machine, provided by Plant Protection Ltd., Jealott's Hill. Each sample was placed in the top sieve in a stack of three of decreasing mesh size (2.8, 2.5 and 2.2mm) and shaken for 2 min. on an electric shaking machine. The weight of grain retained in each sieve was measured and the results were recorded as a percentage of sample larger than the sieve sizes indicated.

~~A rough estimate of the number of fertile tillers per plot was obtained by dividing the grain yield per plot by the mean weight of ears from that plot 108 days after sowing.~~

Fig.12 shows the rainfall during the trial and the fluctuations in soil moisture. The drought channelling effectively lowered soil moisture during the early part of the experiment, but failed to do so in mid-June, when there was very heavy rain. Poor drainage led to a flooding of part of the experimental area at this time, leaving Block I completely under water and affecting plots 17 and 33 also (Fig.10). As a result, no further samples were taken from Block I and results expressed refer only to the three remaining blocks.

During the fine weather in July the soil dried out apparently at similar rates both in the open and under the channelling so that there were again no substantial differences between the soil moistures in the two situations. FIG 12 RAINFALL AND SOIL MOISTURE HELD 1971 40

~~30 RAINFALL~~

~~MM. 20~~

~~APRIL MAY JUNE JULY AUG~~

~~BETWEEN ROWS --- CONTROL 20- L //`, - DROUGHT U MEAN •■••• ,-U 0/03 U =UPPER CORE L 10 L = LOWER CORE L SOIL ■••• U~~

~~MOISTURE DI D2 D3 20 40 60 810 Oo TIME -- DAYS AFTER SOWING -44-~~

Results Fig.13 illustrates the mean yield of grain from each treatment and further details regarding yield are given in Table 6 (Appendix tables 29, 31, 33). There was an 18% reduction in yield where mildew was present and a 30% reduction with take-all, yet with both diseases present yields were reduced only by 32%. No drought treatment significantly affected yield.

Much of the loss with take-all probably resulted from its effect in reducing the number of fertile tillers (Table 7 Appendix table 30), there being relatively little difference in ear dry weight (Table 6 Appendix tables 31, 32, 33 and Fig.15) and grain size (Fig.14 Appendix tables 347 35) between comparable plots with and without take-all. By contrast mildew did not affect the number of fertile tillers but significantly reduced ear dry weight and substantially changed the size composition of the grain (Table 6 and Figs. 14 and 15).

Overall the total shoot weight was not much affected by any treatment though finally there was a difference in this respect between plots with mildew only and those with neither take-all nor mildew (Fig.15 Appendix tables 36 and 37). However, some treatments did affect markedly the size of individual leaves (Table 8 Appendix table 38) and thus the total leaf area produced (Table 9 Appendix table 39 and 4o). For example leaf numbers 3, 4, 6, 8 and 9 on plants from plots with take-all only were significantly smaller than the corresponding leaves from plots with

~~FIG 13~~

~~MEAN GRAIN YIELD PER TREATMENT~~

~~. L.S.D. P 0-05~~

~~•S KG. -46-~~

~~TABLE 6~~

~~FIELD EXPERIMENT 1971~~

~~MEAN TREATMENT YIELDS.~~

~~TREATMENTS DRY WT. L.S.D. DRY WT. L.S.D. YIELD p=0.05 EARS p=0.05 Kg gm~~

~~0 1.93 1.17~~

~~1.58 0.99 . 0.25 0.09 T 1.31 1.26~~

~~T & M 1.27 1.05~~

~~DO 1.66 1.12~~

~~Dl 1.46 1.12 0.34 0.21 D2 1.63 1.21~~

~~D3 1.35 1.02 TABLE 7~~

~~FIELD EXPERIMENT 1971~~

~~MEAN NUMBER OF FERTITE TILLERS IN RELATION TO DROUGHT PERIOD AND DISEASE.~~

~~TREATMENTS MEAN NUMBER L.S.D. OF SHOOTS p=0.05 PER PLOT~~

~~0 1,634~~

~~M 1,65+ .248.80 T 1,040~~

~~T M 1,225~~

~~DO 1,553~~

~~Dl 11304 11058.40 D2 1,376~~

~~D3 1,321~~

~~-48~~

~~FIG 14~~

~~SIEVING TEST DATA~~

~~100 2.8 MM.~~

~~0/0 BO-~~

~~GRAIN • 2.5 MM. SAMPLE 60 -~~

~~PER~~

~~SIEVE 40 > 2•2 MM.~~

~~20-~~

~~< 2.2 MM.~~

~~DO DI D2 D3~~

~~100~~

~~GRAIN~~

~~SAMPLE 60~~

~~PER~~

~~SIEVE 40~~

~~T &M -1+9- FIG Is~~

~~TOTAL SHOOT WT. & EAR WT. IN RELATION~~

~~TO DISEASE~~

~~DRY~~

~~W T.~~

~~DAYS AFTER SOWING -50 - FIG 16~~

~~TOTAL SHOOT WT. & EAR WT. IN RELATION~~

~~TO DROUGHT PERIOD~~

~~2 .0 L.S.D. • DO p 0.05 • DI • D2 • a 3~~

~~1.5~~

~~DRY~~

~~WT. L.S.D. G. p 005~~

~~1.0~~

~~0'5~~

~~20 40 60 100 120~~

~~DAYS AFTER SOWING TABLE 8~~

~~FIELD EXPERIMENT. 1971~~

~~MEAN INDIVIDUAL LEAF AREAS (CM2) IN RELATION TO DROUGHT AND DISEASE~~

~~Treatment Leaf Number 1 2 3 4 5 6 7 8 9~~

0 4.66 7.73 11.68 17.72 24.70 30.05 31.37 28:34 10.46 M 4.67 7.78 11.78 17.02 22.33 27.13 30.64 26.90 10.15 T 4.52 7.57 10.80 14.73 22.53 25.85 29.97 25.48 9.07 T & M 4.58 7.55 11.39 15.33 20.71 26.02 28.84 25.17 8.90 L.S.D. 0.30 0.50 0.75 1.84 2.85 3.11 2.21 1.48 1.22 p=0.05 Do 4.6o 7.60 11.21 15.61 24.02 29.38 31.46 28.38 10.62 D1 4.69 7.83 11.56 15.75 20.14 23.46 25.34 20.61 6.54 D2 4.63 7.22 11.10 16.10 21.87 26.79 31.26 28.06 10.64 D3 4.52 7.98 11.78 17.25 24.23 29.48 32480 28.84 10.79 L.S.D. 0.24 0.60 0.80 2.94 2.33 2.83 3.74 5.84 2.83 p=0.05 Produced in drought period 1 Produced in drought period 2 -52-

~~TABLE 9~~

~~FIELD EXPERIMENT 1971~~

~~MEAN LEAF AREA PRODUCED PER PLANT IN RELATION TO DROUGHT PERIOD AND DISEASE.~~

~~TREATMENTS DAYS AFTER SOWING L.S.D. p=0.05 36 5o 64 78~~

~~DO 42.99 109.50 157.25 157.25~~

~~Dl 47.94 98.00 133.46 133.46 18.6o D2 44.30 101.87 157.01 157.01~~

~~D3 43.24 108.05 163.40 163.40~~

~~0 46.36 111.92 160.39 160.39~~

~~M 48.90 106.82 157.25 157.25 9.47 T 41.18 98.48 146.40 146.4o~~

~~T & M 42.03 100.21 147.07 147.07~~

~~Drought Drought Drought Phase Phase Phase 1 2 3 -53-~~

neither take-all nor mildew. There were similar differences between leaves 4,52 6, 7, 8 and 9 from plots with both mildew and take-all and those from plots with neither disease, but only leaves 8 and 9 from plots with both diseases differed from those with mildew only.

Similar reductions in leaf area which can be attributed to take-all appear in comparisons of total leaf area at 50, 64 and 78 days after sowing between plots with take-all only and those with neither disease at 64 and 78 days between plots with both diseases and those with mildew only (Table 9).

Drought during tillering (treatment Dl) similarly reduced leaf size. Leaves 5, 6, 7, 8 and 9 were significantly smaller than those from non-droughted plots (Table 8) and at 64 and 78 days after sowing the total leaf area was correspondingly less (Table 9). Most of the effect therefore relates to leaves produced long after the droughting treatment was applied. No other drought treatment affected leaf size nor did mildew.

When leaf senescence is taken into account, however, and total leaf areas are converted to green leaf areas, i.e. photosynthetic areas (Table 10 Appendix tables 41, 42) a different picture emerges. Plants infected with mildew show significant reductions in green leaf area 50, 64 and 78 days after sowing. On the last date the reduction was about 50% and this is particularly important because it TABLE 10

~~FIELD EXPERIMENT 1971~~

~~MEAN GREEN LEAF AREA (CM2 ) PER PLANT IN RELATION TO DROUGHT PERIOD AND DISEASE.~~

~~TREATMENTS DAYS AFTER SOWING L.S.D. p=0.05 36 50 64 78~~

~~DO 42.98 87.47 84.03 34.30~~

~~Dl 47.77 77.06 75.19 27.10 14.52 D2 44.28 80.33 82.83 33.50~~

~~D3 43.13 82.4o 88.33 29.76~~

~~0 46.28 96.06 97.63 45.83~~

~~M 48.99 77.46 75.66 23.62 7.46 T 41.07 82.60 90.72 33.06~~

~~T & M 41.93 71.14 66.36 22.10~~

~~Drought Drought Drought Phase Phase Phase 1 2 3 -55-~~

~~occurred at grain filling. Take-all alone had much less effect at this stage and none before that. No drought treatment appeared to affect senescence.~~

A regression analysis of senescence on time for the four different treatments (Fig.17 and Table 11 Appendix tables )f3 and 44), suggests that mildew accelerates the onset of senescence rather than the rate at which it proceeds. Thus the intercepts of the lines for plots with mildew and those without differ, but not the slopes (Fig.17).

Mildew was effectively controlled throughout the experiment on plots shown with ethirimol-dressed seed (Table 12 Appendix table 45) and since mildew level was little affected by the drought treatments it can also be inferred that neither to any great extent was the uptake of ethirimol by the plant. However, the level of mildew was reduced on plants with take-all (Table 12 Appendix table 1+6) and conversely take-all infection was greater on plants also infected with mildew (Table 13 Appendix table 47),

The level of take-all did not appear to be affected in any way by the drought treatments, but plots with take-all were clearly distinguished in the field from the rest by the shorter shoots (Table 14 Appendix table 48), fewer fertile tillers and increased weed growth. -56-

~~TABLE 11 FIELD EXPERIMENT 1971~~

~~REGRESSION LINES OF PERCENTAGE SENESCENCE PER PLANT AGAINST TIME (DAYS AFTER SOWING) IN RELATION TO DROUGHT PERIOD AND DISEASE.~~

~~Treatments Regression Intercept S.E. Overall Coeff between estimate Slopes of slope~~

~~0 1.35 -46.89~~

~~1.29 -34.22 + 1.237 1.32 T 1.41 -49.09~~

~~T & M 1.24 -30.03~~

~~DO 1.32 -40.76~~

~~D1 1.33 -40.50 ± 0.51 1.32 D2 1.33 -41.03~~

~~D3 1.33 -39.22~~

~~Correlation coefficient of senescence per plant (mildew infected) against time = 0.9585 FIG 17 FITTED REGRESSION LINES - ANGULAR TRANSFORMATION OF 0/0 SENESCENCE AGAINST T1 ME IN RELATION TO~~

~~DISEASE (FIELD 1971) 60 I / ANGULAR ,~~

~~TRANSFORM %." k OF 0/0 40~~

~~SENESCENCE~~

~~PER PLANT~~

~~OVERALL SLOPE - 1.32 20~~

~~20 40 60 80~~

~~TIME -- DAYS AFTER SOWING -58-~~

~~TABLE 12~~

~~FIELD EXPERIMENT 1971~~

~~%MILDEW PER PLANT IN RELATION TO DROUGHT PERIOD AND DISEASE.-~~

~~TREATMENTS DAYS AFTER SOWING L.S.D. p=0.05 36 5o 64 78~~

~~DO 0.12 0.67 3.41 5.89~~

~~D1 0.05 0.31 2.22 5.37 0.32 D2 0.14 0.81 2.88 5.04~~

~~3 ().i4 0.64 3.40 7.4o~~

~~- 0.09 0.54 1.36~~

~~II 0.21 1.22 6.22 17.60 0.20 T - o.o6 0.64 0.73~~

~~T & M 0.22 1.29 6.20 10.62~~

~~Drought Drought Drought Phase Phase Phase 1 2 3 -59-~~

~~TABLE 13~~

~~FIELD EXP;Ii;RIMENT 1971~~

~~MEAN TAKE-ALL DISEASE INDEX PER TREATMENT.~~

~~TREATMENT DISEASE INDEX L.S.D. p=0.05~~

~~DO 45.55~~

~~D1 46.31 11.32 D2 46.18~~

~~D3 46.30~~

~~0 7.58~~

~~M 12.62 7.65 T 75.97~~

~~T & m 88.18 -6o-~~

~~TABLE 14~~

~~FIELD EXPERIMENT 1971~~

~~MEAN SHOOT HEIGHT (CM) IN RELATION TO DROUGHT PERIOD AND DISEASE.~~

~~TREATMENTS DAYS AFTER SOWING L.S.D. p=0.05 36 5o 64~~

~~0 34.21 58.58 79.13~~

~~M 36.15 55.73 79.95 6.16 T 30.81 51.46 71.26~~

~~T & M 31.90 53.82 72.32~~

~~DO 33.03 58.86 78.13~~

~~D1 34.65 51.13 71.41 7.48 D2 32.71 52.83 76.64~~

~~D3 32.48 56.97 76.48 -61-~~

~~(ii) Si221ementary_ experiments wittia.grAninis~~

Results from the 1971 field trial indicated. that the level of take-all was greater on plants with mildew than those grown from ethirimol-dressed seed. So, possibly, ethirimol affects the development of G. graminis. This was studied in two experiments. The first examined the effect of ethirimol applied directly to the fungus and the second the growth of the fungus along roots from ethirimol-treated seeds.

~~A) Ethirimol applied directly to G. graminis~~

Different quantities of a suspension of ethirimol in sterile water were added to molten 2% malt agar at c 40 - 459C to give three agar preparations with final concentrations of 0.08%, 0.8% and 8% ethirimol w/w. Ten plates were then poured of each ethirimol level.

Thirty more petri dishes were prepared in a similar way with a suspension of 'Ceresan' to give ten plates each of 0.08%, 0.8% and 8% Ceresan in the agar. A further ten plates were prepared using sterile water to act as a control.

When the plates were cool a mycelial plug, 7mm diameter, cut aseptically from a culture of G. graminis on 2% malt agar, was placed in the centre of each. All the plates were then incubated at 23°C for 10 days and the diameters of the resulting mycelial mats of -62

~~G. graminis were measured daily. The results are shown in Fig.18 (Appendix table )+9).~~

There was no growth whatsoever on agar with 'Ceresan' or on agar with 8% ethirimol, but there was growth at the two lower concentrations of ethirimol, though initially at a slower rate than the control.

After 5 days six grains of barley were placed •into each of five of the control plates as shown in Fig.19. Two grains were treated with 'Ceresan', two with ethirimol (both at commercial rates) and the remainder were untreated controls. The growth of the fungus was observed after a further 4 days ,Fig.20.

'Ceresan' caused complete inhibition of the fungus, but ethirimol may limit the growth of G. graminis the effect of the recommended commercial application (equivalent to 0.8% w/w on the seed) is likely to be small.

~~B) Ethirimol applied indirectly to G.raminis on treated grain.~~

Seeds of barley either untreated or those treated with ethirimol and 'Ceresan' as before were sown singly on strips of damp blotting paper laid over a glass slide (17.0 x 2.5cm) (Fig.21.) Each seed was held in place by a further strip of damp blotting paper wrapped around it and the slide. Each slide was then inserted into a 8•0 11 CONTROL C)

~~0.08 % ETHIRIMOL~~

~~19 co 2: 0~~

~~1. 0 - 6 0/0 M 11~~

~~6-0 8 0/0 . HI • V3 31 40~~

~~DIAMETER 0 '9 .~~

~~OF I COLONY H / I CM. IINVb9~~

~~4'0 IN 3 S 1 1H~~

~~1 0~~

~~117 z A1~~

~~/ 1 0~~

~~1 > - 0 > m 2.0 -o r > H m U, • II E--. a gi--E a 4 8 8 10~~

~~DAYS AFTER INOCULATION -64-~~

~~FIG 19 CERESAN~~

~~E THIRIMOL~~

~~DRESSED~~

~~Growth of G. graminis after 5 days at 23°C- on 2% Malt Agar and pattern of applying treated grains.~~

~~FIG 20~~

~~Growth of G. raminis after 9 days, showing inhibition caused by 'Ceresan' treated grain. -65-~~

~~FIG 21~~

~~GROWTH OF G. GRAMINIS ALONG ROOTS~~

~~BOILING~~

~~TUBE BLOTTING~~

~~PAPER BARLEY MYCELIAL GRAIN PLUG~~

~~GLASS- SLIDE~~

~~FIG 22~~

~~RACK SUPPORTING BOILING- TUBES -66-~~

boiling tube (19.0 x 3.5cm) which was plugged with cotton wool, and the tubes placed in a specially constructed rack (Fig.22). This was covered with black polythene to exclude light and kept in a room at 23°C.

When the roots had extended c 4 cms beyond its blotting paper wrap a mycelial plug of G. graminis cut aseptically from a culture on 2% malt agar was placed (mycelium downwards) alongside one root in each tube. The growth of the fungus was then recorded daily, especially the extension of the black runner hyphae along the roots.

~~After 4 or 5 days the cotton wool plugs were adjusted to allow the growth of the shoot out of the tube.~~

Although not completely successful because the fungus did not grow along all roots, some results are shown in Table 15. These generally indicate that treating seed with ethirimol or 'Ceresan' has no effect on the growth of G. graminis along the roots of that plant. It is likely therefore that differences in take-all levels noted in the previous experiment result from factors other than the chemical used. TABLE 15 GROWTH OF G. GRAMINIS ALONG TREATED ROOTS

~~Treatment No. of roots No. showing growth Mean growth of~~

~~examined of G. graminis hyph44 after 6 days at 23°C~~

~~Control 28 20 13.25 mm~~

~~Ethirimol 24 15 12.50 mm~~

~~Ceresan 6 10.00 mm -68-~~

~~(iii) Field Experiment 1972 a) Mildew asughLzaleraatian~~

In the 1971 experiment droughting the crop during tillering affected the amount of leaf tissue which was subsequently produced though it did not alter the mildew levels. In 1972 the effects of drought and mildew were re-examined in an experiment of simplified design. This had four blocks each with two main plots (drought (D) and no drought (Do)) split into two sub-plots (mildew (M) and no mildew (0)) (Fig.23). Plots were subjected to drought by placing plastic channelling between rows as in 1971 and mildew was controlled by sowing 'no mildew' plots with seed dressed with ethirimol.

Plots were sown on 17 April and the drought channelling laid down on 18 May (31 days after sowing). Assessment of leaf area, mildew infection and senescence were carried out as in 1971 every 10 days on a sample of ten plants per plot from 1 June (45 days after sowing) until 17 July (91 days after sowing) when all leaves had senesced.

~~The number of fertile tillers per plot was assessed from counts of the number of tillers in five 1 ft. row lengths, made when all ears had emerged.~~

~~The experiment was harvested, as before, on~~

~~-69- FIG 23 EXPERIMENTAL LAYOUT~~

~~MILDEW - DROUGHT INTER ACTION 1972~~

~~I 2. 3 4~~

~~D BLOCK I~~

~~M 1 0 M 1 0~~

~~1 1 5 6 7 8~~

~~Do D BLOCK II~~

~~M 1 0 0 1 M Do = NO DROUGHT~~

~~D = DROUGHT~~

~~1 9 10 II 12~~

~~Do D 0 = CONTROL BLOCK III M MILDEW 0 1 M 0 1 M~~

~~13 14 15 I 16~~

~~D Do BLOCK a 1 t. M1 0 M 1 0 -70-~~

~~16 August (121 days after sowing) and grain subjected to a sieving test as previously described ( p. 42 ).~~

~~Results~~

The results show that droughting affected measured parameters less markedly than in 1971. Indeed the yield from droughted plots was marginally though not significantly higher than that from the others. Probably this can be attributed to the dry season (Fig.24), if anything the drought channelling tended to conserve moisture and so favour grain development.

Mildew was again extensive on untreated plots and well controlled by ethirimol with the droughting treatment, not unexpectedly, showing no effect on this control (Fig. 25 Appendix table 50). On those plots where mildew was allowed to develop yields were significantly lower. In this instance (c.f. 1971) there were fewer tillers but the main effect appeared to be a reduction in the size of grain from plots with mildew (Table 16 Appendix tables 51, 52, 53, 54). Droughting also reduced tillers slightly but, in contrast to mildew, increased grain size, as indicated above.

Neither droughting nor Mildew influenced the size of individual leaves (Table 17 Appendix table 55 or the total leaf area (Fig.26 Appendix table 56, 57) but correction for senescence show that mildew had a

~~FIG 24 RAINFALL FIELD 1972 SILWOOD PARK~~

~~,A 1NFALL 20 MM. r I0~~

~~APRIL MAY JUNE JULY AUGUST~~

~~I 2b 4b b 810 100 120~~

~~DAYS AFTER SOW 1NG -72-~~

~~TABLE 16~~

~~FIELD EXPERIMENT 1972~~

~~MEAN YIELD OF GRAIN, NUMBER OF TILLERS AND GRAIN SIZE IN' RELATION TO DROUGHT AND MILDEW.~~

~~TREATMENTS YIELD NO. FERTILE % GRAIN SAMPLE Kg TILLERS 2.8 mm~~

~~Do 0 1.98 3,964 1.8~~

~~Do M 1.77 3,191 1.5~~

~~D 0 2.07 3,285 4.6~~

~~D M 1.43 2,970 1.5~~

~~L.S.D. 0.44 420 2.0 p=0.05 0 2.03 3,575- 3.1~~

~~1.60 3,080 1.4~~

~~L.S.D. 0.16 297 1.6 p=0.05 Do 1.88 3,528 1.6~~

~~D 1.75 3,128 2.75~~

~~L.S.D. 0.70 380 0.90 p=0.05 TABLE 17~~

~~FIELD EXPERIMENT 1972. MEAN INDIVIDUAL LEAF AREAS (CM2) IN RELATION TO DROUGHT AND MILDEW~~

~~Treatment Leaf Number 1 2 3 5 6 7 8 9~~

~~Do 3.47 5.11 8.04 13.02 18.50 23.61 24.67 17.06 5.07 D 3.53 5.46 8.83 14.35 20.03 24.17 24.73 15.93 5.16~~

~~L.S.D. 0.10 0.37 0.69 1.41 1.97 1.45 1.90 1.19 0.75 p=0.05 0 3.53 5.31 8.42 13.98 17.55 24.33 24.91 16.22 5.00 M 3.47 5.26 8.45 13.39 20.98 23.45 24.49 16.77 5.22~~

~~L.S.D. -0.50 0.38 0.40 0.84 2.18 0.49 1.55 1.73 0.80 p=0.05 • KEY TO FIGURES 25- 27~~

~~o Do 0 - NO DROUGHT - CON TROL~~

~~Do M - NO DROUGHT MILDEW~~

~~0 D 0 - DROUGHT - CONTROL~~

~~D M - DROUGHT - MILDEW -75.-~~

~~FIG 25~~

~~0/0 MILDEW INFECT1ON PER PLAN T~~

~~IN RELATION TO TREATMEN TS~~

~~DAYS A F TER SOWING -76-~~

~~FIG 26~~

~~TOTAL LEAF AREA PRODUCED PER~~

~~PLANT IN RELATION TO TREATMENTS~~

~~120~~

~~AREA~~

~~2 CM~~

~~40 60 80 100~~

~~DAYS A F TER SOW I N G -77-~~

~~FIG 27~~

~~GREEN LEAF AREA PER PLANT IN~~

~~RELATION TO TREATMENTS~~

~~80-~~

~~AREA~~

~~40 CM2~~

~~40 60 80 160~~

~~DAYS A F TER SOWING -78-~~

considerable effect on the green leaf area present at any time (Fig.27 Appendix 58, 59). This was especially marked on 5 July (79 days after sowing)) when the ears had first emerged. Regressions of senescence on time (Fig. 28 and Table 18 Appendix table 60, 61) again indicate that mildew hastens the onset of senescence but does not significantly alter its subsequent rate. -79-

~~TABLE 18~~

~~FIELD EXPERIMENT 1972~~

~~REGRESSION LINES ANGULAR TRANSFORM % SENESCENCE PER PLANT AGAINST TIME IN RELATION TO DROUGHT AND MILDEW~~

~~TREATMENTS SLOPE INTERCEPT OVERALL ESTIMATE OF SLOPE~~

~~Do 1.29 -45.10 1.30 D 1.32 -44.73~~

~~L.S.D. 1.05 - p=0.05 0 1.34 -52.81 1.30 M 1.26 -36.29~~

~~L.S.D. 2.03 p=0.05~~

~~ANGULAR TRANSFORMATIONOF PER PLANTAGAINSTTIMEINRELATIONTO FIG 28 O NN~~

~~N DROUGHT ANDMILDEW N OV ERALL ESTI MA T E NN NN 4/ N FITTED REGRESSIONLINES 0 co 0 11. 0. Cl) w O N N ‘1/ -80 x 0~~

~~N N N N~~

~~■ N , N e 6' .~~

~~D di Nop N 42 , 0 \N / 0 SENESCENCE~~

~~,D.,,,, O N, oN~~

~~oi ONN N _0<~~

~~NN N - O .0 cv 0 , zt~~

~~LLI u_ --.- I- cr z~~

~~-81-~~

~~b) Mildew take-all interaction with addition of spray timing~~

A second field trial in 1972 attempted to examine further the take-all/mildew interaction. In this it was hoped to limit mildew infection (on main plots) to specific growth phases, as in the greenhouse experiment of 1971, by applying ethirimol as a spray to below 'run-off' point. These periods were : A tillering (G.S. 1 - 5) ; B stem extension (G.S. 6 - 9) and C grain filling (G.S. 10 - 11). Within these main plots specific sub-plots were seeded with G. graminis on grain as described on page 17. In the event it was found impossible to spray the crop as desired during the early growth, mainly because prevailing winds caused excessive drift of the low- volume sprays and application of higher volumes to overcome this led to run-off. As a result mildew became established early in plots where it should have been controlled.

For this reason the experimental design was ammended to that shown in Fig. 29, part of the experimental area being abandoned, and the rest divided into four blocks. Treatments were limited to spraying at higher volumes as described on p 14 over the periods shown :-

~~BLOCK I BLOCK II 1111 -~~

~~%.0~~

~~1 2 3 4 5 6 10 1I 12 13 14 15 16 M34 - VI~~

~~N T T T T T T T T >I X3~~

~~ra V-3 1d3d~~

~~rn 71 0 SB SC SB+C SB SB+C SC NS NS SC SB NS SB+C SB SB+C SC NS rn 0 N301 VI 1~~

~~V831N1 BLOCK ZE r BLOCK IlI D --< LL 0 c) 3 17 18 19 20 21 2 2 2 3 24 25 26 27 28 29 30 31 32 NO~~

~~T T T T T T T T~~

~~NS NS SC SB+C SB SB+C SC SB SB SB+C NS SC SC SB+C SB NS - -83-~~

~~S.B. - Spray during stem extension S.C. - Spray during grain filling S.B.+ C. Spray at both times~~

This amounted in practice to one spray application at the beginning of each growth phase. Two plots of each treatment were present in each block, one having been inoculated with G. graminis the other not.

~~The experiment was sown on 6 April and sprays were applied on 6 June and 20 June (61 and 75 days after sowing).~~

~~Measurements of leaf area, mildew infection and senescence were carried out on ten plants per plot on the following dates :~~

~~Days after sowing 24 May 48 2 June 57 13 June 68 26 June 82 10 July 96~~

~~Take-all infection was assessed on each plot as described previously (p. 38).~~

~~The crop was harvested on 15 August (132 days after sowing) and was treated as before (p. 40 and 42). -94-~~

Unfortunately, when the roots were examined for take-all, none was found and so one of the basic objectives of the experiment was not fulfilled. The lack of infection remains unexplained. The remaining data provide further evidence of the effects of mildew, many of which have been already noted.

The effect of a spraying during stem extension is shown in Fig.30 Appendix table 62 and the benefit to yield in Table 19 Appendix table 63 and these results confirm therefore, part of the 1971 greenhouse experiment. Mildew again had no effect on the total leaf area (Fig.31 Appendix table 64)but did affect senescence (Figs. 32 and 33 Table 20 Appendix table 65, 66, 67) though the differences between treatments are less striking than those shown in the previous experiments. -85-

~~TABLE 19~~

~~FIELD EXPERIMENT 1972~~

~~MEAN GRAIN YIELD IN RELATION TO TIME OF SPRAY APPLICATION.~~

~~Treatments Yield Kg~~

~~No Sprays 3.168~~

~~Spray B 3.99)+ (Stem Extension)~~

~~Spray C 3.462 (Grain Filling)~~

~~Spray B C •3.90~~

~~L.S.D. 0.513 p=0.05 -86-~~

~~KEY TO FIGURES 30 - 32~~

~~• NO SPRAY~~

~~SPRAY STEM EXTENSION - B~~

~~SPRAY GRAIN FILLING - C~~

~~SPRAY BOTH PERIODS - B+C -87-~~

~~FIG JO~~

~~% MILDEW INFECTION PER PLANT~~

~~IN RELATION TO TIME OF SPRAY~~

~~APPLICATION~~

~~SPRAY SPRAY B *C~~

~~0/0~~

~~50 70 90~~

~~DAYS AFTER SOWING -98-~~

~~FIG 31~~

~~TOTAL LEAF AREA PRODUCED PER PLANT~~

~~IN RELATION TO TIME OF SPRAY~~

~~APPLICATION~~

~~160~~

~~120~~

~~AREA~~

~~CM2~~

~~41, Ak SPRAY SPRAY~~

~~sb 7b 90~~

~~DAYS AFTER SOWING FIG 32~~

~~GREEN LEAF AREA PER PLANT IN~~

~~RELATION TO TIME OF SPRAY~~

~~APPLICATION~~

~~SPRAY SPRAY C~~

~~AREA~~

~~2 CM~~

~~DAYS AFTER SOWING -90-~~

~~TABLE 20~~

~~FIELD EXPERIMENT 1972~~

~~REGRESSION LINES ANGULAR TRANSFORM % SENESCENCE AGAINST TIME IN RELATION TO SPRAY APPLICATION.~~

~~Treatments Slope Intercept Overall Slope~~

~~No Sprays 0.96 -26.69~~

~~Spray B Q. 95 -31.66 (Stem Extension) 0.90 Spray C (Grain Filling) 0.87 -23.95~~

~~Spray B + C 0.84 -26.29~~

~~L.S.D. 1.27 p=0.05 -91-~~

~~FIG 33~~

~~FITTED REGRESSION LINES - ANGULAR~~

~~TRANSFORM OF 0/0 SENESCENCE PER PLAN T~~

~~AGAINST TIME I N RELATION TO SPRAY~~

~~APPLICATION -92-~~

~~C CHLOROPHYLL LEVELS IN HEALTHY AND INFECTED PLANTS~~

Preceding experiments have developed the idea that mildew initiates senescence prematurely and that the resulting, more rapid decrease in photosynthetic area leads to reduced growth. However, in these situations ethirimol was used to control mildew so a comparison between mildew-free and mildewed plants was always confounded with one involving ethirimol-treated versus untreated plants. It was decided, therefore, to investigate the onset of senescence in situations where, by the use of spore-free cabinets, plants could be grown free of mildew without the use of chemicals. In these experiments, the amounts of chlorophyll a and b in leaves were used as a measure of photosynthetic potential rather than subjective measurements of the degree of senescence.

~~Experiment (1)~~

Thirty-six Sin. (7.5cm) pots of a peat and sand mixture were each sown with one grain of barley (p. 17) on 19 April 1972. Eighteen of the pots were randomly arranged within a spore-free cabinet while the other eighteen were placed in a similar cabinet designed to contain the mildew infection. The cabinets are described in Materials and Methods ( p. 18). -93 -

On 1 May (12 days after sowing) the seedlings in one cabinet were inoculated with conidia of E. graminis by shaking heavily infected plants over them. Subsequently, the mildew infection was allowed to develop naturally.

The first measurement of chlorophyll content was made on 4 May (15 days after sowing). Three pots were taken from each cabinet and the leaf area, mildew infection and senescence assessed on each plant. The chlorophyll was then extracted from the three first leaves of each treatment using a modification of Bruinsma's (1963) method described in Materials and Methods (p. 21). In this case the chlorophyll was extracted in acetone, and the quantity expressed in mg of chlorophyll per cm2 of leaf area. Chlorophyll was also extracted from two of the three second leaves available, selected at random.

The sampling procedure was repeated on the 9, 14, 18 May (20, 25 and 30 days after sowing respectively), with the exception that with leaves number three upwards, only one leaf from those available for each treatment was selected for chlorophyll assessment.

~~ResultS,,.~~

Table 21 shows the pattern of growth exhibited by the plants in the experiment. It supports previous findings that mildew has very little effect on the leaf area produced but leads to premature senescence as TABLE 21

~~GROWTH PARAMETERS MEASURED OVER 4 SAMPLING DATES IN RELATION TO MILDEW INFECTION~~

~~Treatment Sample Days after Mean leaf Mean green No. sowing area leaf Mildew Senescence produced (cm2) area~~

~~Control 19.25 19.25 IWO ONO Mildew 15 21.20 21.20 0.41~~

~~Control 38.55 38.55 Oa/ 2 20 Mildew 32.70 31.63 2.58 3.28~~

~~Control 53.97 53.97 Mildew 3 25 59.56 53.21 9.69 11.11~~

~~Control 72.35 72.35 Oar 30 Mildew 70.57 54.31 8.47 23.01+ -95-~~

demonstrated by the green leaf area in sample 4 (30 days after sowing). The control plants showed no senescence at all within the period of the experiment, while nearly 25% senescence only 29 days after the initial mildew inoculation was shown by infected plants.

The chlorophyll levels of the various leaves are shown in Fig.3+ Appendix table 68 and reflect the rapid senescence of infected leaves. Also an interesting fact emerges, that successively produced leaves do not seem to have as high an initial chlorophyll content as the first and second leaves.

~~Mildew appears to be present on the leaf some 7 - 10 days before causing rapid senescence i.e. 2 or 3 days after the production of visible pustules.~~

~~Experiment (2)~~

This experiment was designed to examine the effect of ethirimol on the growth of barley in the presence or absence of mildew infection. Plants were kept free of mildew using the spore-free cabinets as before.

~~Seeds were sown singly in 3in. (7.5cm) pots of peat and sand mixture on 14 January 1973. The experiment was set up as a split plot design having four treatments as below : FIG 34~~

~~QUANTITY OF CHLOROPHYLLS A & B (MG/CM2 )~~

~~CONTAINED WI THIN THE INITIAL LEAVES~~

~~IN RELATION TO MILDEW INFECTION~~

~~AND TIME~~

~~LEAF NUMBER~~

~~0 = CONTROL~~

~~MILDEW INFECTED~~

~~CHLOROPHYLL A~~

~~CHLOROPHYLL B LI L2 LI L2 U L2 L3 LI L2 L3 LI L2 L3 L4 LI L2LS L4 L2L3I4 L5 LI LL3 L4 1.5 0 0 0 M~~

~~SAMPLE I SAMPLE 2 SAMPLE 3 • SAMPLE -99--~~

~~Spore-free cabinet tMildew'cabinet Control Ethirimol treated Control Ethirimol treated~~

~~The pots were randomly arranged within each cabinet, and where required grain was treated with ethirimol at the rate of 0.8% w/w a.i. on the seed.~~

~~On 24 January (10 days after sowing) plants infected with mildew were shaken over the plants within the 'mildew' cabinet. After this mildew infection was allowed to progress naturally.~~

The first sample for chlorophyll determination was taken on 31 January (17 days after sowing) and thereafter every 3 days until 44 days after sowing i.e. ten samples. Five plants from each treatment were selected at random, the leaf area, mildew infection and senescence of these measured as before (p 93 ). The chlorophyll was then extracted using the second method (p 22 ) i.e. With methanol as solvent. The remaining plant material was dried, weighed and the quantity of chlorophyll per plant expressed in mg/g of this dry weight.

~~Results~~

Mildew again had little effect on leaf area (Fig.35 Appendix tables 69, 70) but by sample 10 there was a significant difference in this respect between ethirimol-treated and untreated plants. This difference is reflected in the slightly greater green leaf area of -99-

ethirimol-treated plants over those not so treated but kept in a mildew-free cabinet (Fig.36 Appendix tables 71, 72). The major effect of the chemical in reducing senescence through mildew control is clearly seen in this figure.

However, one of the most interesting effects relates to shoot dry weight of ethirimol-treated plants in a 'mildew-environment' (Fig.37 Appendix table 73 and 7+). This was significantly greater than that from any other treatment. Correspondingly, so was the root dry weight (Fig.38 Appendix table 75, 76). The possible significance is discussed later.

Plants with mildew show substantial loss of root dry weight, and significantly, this effect appears first (Fig.39) at the time when green leaf area of these plants departs significantly from that of plants in the other treatments (Fig.36).

The chlorophyll levels (mg/g) of the treatments during the experiment is shown in Fig.39 Appendix table 77. These values were found to exhibit a straight line relationship and therefore regression lines have been drawn Fig.40 Table 22 Appendix table 78.

~~This demonstrates a point made in the last experiment that leaves after 1 and 2 are produced with less chlorophyll per cm2 or per g. Since there is no -100-~~

~~KEY TO FIGURES 35- 40~~

~~NO o - CON TROL~~

~~ETHIRIMOL o MILDEW~~

~~ETHIRIMOL- - CONTROL~~

~~DRESSED m - MILDEW -101- FIG 35~~

~~M EAN LEAF AREA PRO DUCE D PER PLAN T~~

~~IN RELATION TO INFECTION AND CHEMICAL~~

~~TREATMENT~~

~~O fl O a.~~

~~2 U -102-~~

~~FIG 36~~

~~MEAN GREEN LEAF AREA PER PLAN T~~

~~IN RELATION TO INFECTION AND CHEMICAL~~

~~TREATMEN T~~

~~(9 Z_~~

~~0 tn~~

~~cX w 1- u. <~~

~~U) >- 0~~

~~(NI 2 () -103-~~

~~FIG 37~~

~~MEAN SHOOT DRY WEIGHTS IN~~

~~RELATION TO IN FECTION AND CHEMICAL~~

~~TREATMENT FIG 38~~

~~MEAN ROOT DRY WEIGHTS IN~~

~~RELATION TO INFECTION AND CHEMICAL~~

~~TREATMENT~~

~~ci 9 vi 0 _I a_~~

~~(9 z~~

~~0 U)~~

~~cr w Lt.~~

~~)- cc -105—~~

~~FIG 39~~

~~MEAN TOTAL CHLOROPHYLL LEVELS MG./G.~~

~~PER PLANT IN RELATION TO INFECTION~~

~~AND CHEMICAL TREATMENT~~

~~_,0~~

~~0 U) _0 cc w u.~~

~~U) >-~~

~~0 0 0 ce) cv~~

~~CHLOROPHYLL MG.! G. -10 6 -~~

~~F 1G 40~~

~~Fl TTED REGRESSION LINES - TOTAL~~

~~CHLOROPHYLL LEVEL MG./ G. AGAINST~~

~~TIME IN RELATION TO INFECTION~~

~~AND CHEMICAL TREATMENT~~

~~0 / g / /~~

~~/ / / /~~

~~CHLOROPHYLL MG./G. -107-~~

~~TABLE 22~~

~~REGRESSION OF TOTAL CHLOROPHYLL AGAINST TIME IN RELATION TO INFECTION AND CHEMICAL TREATMENT.~~

~~Treatment Intercept Regression L.S.D. Coeff p=0.05~~

~~No Milstem No Mildew +35.50 -0.50~~

~~Milstem No Mildew +36.77 -0.56 + 0.72 No Milstem Mildew +35.57 -0.62~~

~~Milstem Mildew +35.15 -0.52~~

~~Correlation of total chlorophyll per plant against time in control situation~~

~~-0.917 -108-~~

significant difference in either the slopes or intercepts of these lines, we could postulate that although senescence is occurring in mildew infected plants, there may be some compensation with regard to the amount of chlorophyll initially produced in leaves higher up the plant.

A third experiment was designed to further investigate the interaction between ethirimol and mildew on the plant and also the take-all mildew interaction noted in the field in 1971. However, due to circumstances beyond our control, there was unfortunately found to be no take-all evident when roots were examined. Also, extremely high levels of mildew caused some anomalous results, and as the experiment yielded no new information on either of the interactions considered, it has been omitted from this section, but a more detailed account is recorded in Appendix III. -109-

~~DISCUSSION~~

Earlier experiments which have sought to investigate the effects of mildew on the growth of barley have been limited in their success by the nature of the methods used to control infection. The experiments of Last (1955, 1962) used sprays of lime-sulphur to control mildew infection. The development of ethirimol by I.C.I. Plant Protection Ltd., (Bebbington et al, 1969) allowed us to assess the effects of mildew more critically, in particular by limiting the period of infection. Erysiihe graminis DC. seems less dependent on weather than other foliar pathogens of barley (Brooks, 1972) and therefore can attack very early in the life of the crop. Critical estimates of the yield losses caused by mildew (Large and. Doling, 1962) are based on as,3essments of the level of mildew at heading though it has been noted that an early attack of mildew decreases plant vigour and the size of all plant parts especially the root system (Last, 1962). This was further confirmed by Paulech (1969) and Brooks (1972) who noted that these severe mildew attacks were usually limited to winter barley, but occasionally spring barley could suffer the same fate.

~~These observations led to the questions to which we have in this work attempted to find answers :~~

~~What is the effect of mildew at various stages in growth and how do natural infections influence yield? -110-~~

Using ethirimol in the first glasshouse experiment we were able to limit mildew infections to three major periods of plant growth (A) Tillering, (B) Stem extension, (C) Heading. Yield loss seemed to be greatest when infection occurred during stem extension. In part this results from the rapid production of susceptible tissue at this time but an increase in susceptibility cannot be discounted. Whatever the underlying reason in most years infection in the field reaches its peak during this stage also, and the weather is often more favourable for mildew development at this stage.

However, the effect of infection by Et_gratinis during tillering only, was also noted as being quite severe, (although no infection would be registered over the period chosen by Large and Doling). This decrease in yield may have been due in part to a reduction in tiller number, but this could not be ascertained in this experiment because of the abnormal later growth. A reduction in tiller number when early mildew attacks occur has been noted by Last (1962) and Brooks (1972). This, however, may not have been the sole cause in the experiment as there was no reduction in the dry weight of whole plants which suggests no loss of tiller number. Possibly, early reduction in the size of the root system markedly affected the subsequent growth of the plant.

The yields from the various treatments suggest that some compensation in host growth may occur following mildew attach although this could be a result perculiar to the artificial conditions within the glasshouse.

A major fact noted was that mildew infection did not bring about a change in the size of individual leaves produced on the plants, and therefore there was very little difference in the total area of leaves produced under the various infection periods. Last (1962), however, noted large scale reductions in leaf area brought about by mildew infection but in his measurement of leaf area used two different constants for the calculation of the areas of inoculated and non- inoculated leaves; this, to account for the premature death of the tips of leaves of inoculated plants. This corresponds roughly to the corrections made in this work for the amount of senescence. When considering these figures we do note a loss in leaf area. For example, samples taken 37 days after sowing showed 15-20% leaf senescence while still in the tillering phase. This became progressively more extensive during stem extension e.g. 57 days after sowing infected plants showed up to 60% leaf senescence, while plants on which mildew was controlled showed approximately 25% senescence.

The effect which mildew has on the duration of photosynthetic tissue was also evident in the field trials. These, especially the first, show the number of complex factors which interact in determining the yield of cereal crops (Brooks, 1972). -112-

The first (1971) trial illustrates that the losses caused by take-all are due to a reduction in the number of fertile tillers, while the losses caused by mildew relate to the smaller grain produced by infected plants, the natural field infection of mildew not being early or severe enough to lead to a reduction in tiller number.

Both Last (1962) and Brooks (1972) have commented that they feel yield reductions would be very severe if plants were infected with both G. graminis and E. graminis. This was found not to be so; the yield reduction with both pathogens present was only marginally greater than that from take-all alone. The reasons for this 'non-additive' effect are not clear but certainly there was a significant reduction in the level of mildew where take-all was present. The reason for this is not known; there may be some competition for substrates within the plant. Also there was a significant increase in the level of take-all when mildew was present. This observation agrees with the ideas of Brooks and Last that a plant with a reduced root system (due to mildew attack) is unable to grow away from infection by G. graminis and therefore becomes more severely affected.

Mildew caused very little change in leaf area, whereas take-all and also drought during tillering caused reductions in the sizes of leaves produced. This may indicate that a reduction in the efficiency of the root system at a particular time can cause subsequent reductions in the growth of the plant, especially when this occurs early, during tillering. This may partly -113- explain the stunting of plants f011owing very early mildew attacks (Last, 1962, Brooks, 1972) since the root system is reduced both in size and efficiency. This is also demonstrated by the work of Dale and Felippe (1972) who have shown the importance of first leaf photosynthesis on root development in barley.

~~Apart from this the drought treatment. had very little effect, mainly due to their inherent inefficiency and the weather during the period of the experiment.~~

~~Field trials in 1972 gave a very similar picture with drought having little effect, but mildew hastening the onset of senescence and markedly reducing yields.~~

As has been discussed (Literature Review page 9) most of the assimilates which pass into the grain do in fact come from the ear itself and the flag leaf and sheath. Only 15% of the assimilates pass from the leaves below the flag leaf. However, if mildew causes a premature senescence of the lower leaves and also of the flag leaf itself, the effect on yield is obvious. There may also be a redistribution of the products of photosynthesis as a result of the mildew infection. Edwards and Allen (1966) showed that the products of photosynthesis from a leaf infected with powdery mildew passed rapidly into the parasite mainly in the form of sucrose which was then quickly metabolised into many compounds. They found that the photosynthetic uptake of 14CO2 by the mildew-host complex decreased steadily after inoculation and this we feel reflects a steady -114-

~~decline in the level of chlorophyll present in the leaf.~~

The chlorophyll experiments have shown that senescence is related to a rapid loss of chlorophyll from the leaf tissue about 7-10 days after inoculation with E,gramLn.i2. The 'killing' effect of mildew On leaf tissue was discussed by Last (1955, 1962) and taken into account in Large and Doling's calculations of the severity of mildew infection. However, we have noted that senescence proceeds at a definite rate and the degree of senescence recorded will therefore depend on the time after the initiation of senescence at which one examines the leaf. Therefore, on Large and Doling's scale the percentage of mildew assessed would alter leading to discrepancies in the calculation of percentage yield loss. Last (1963) arrived at a figure of percentage yield loss as being 5 times the square root of the mildew percentage at growth stage 10.5 not 2.5 times this latter value as did Large and Doling; and the above may be the reason for this difference. It is surprising that mildew does not in fact accelerate the process of senescence, it merely appears to trigger it earlier in the life of the leaf. The speed at which this triggering takes place may be dependent upon the amount of mildew present i.e. there may be a threshold infection level above which senescence is rapidly initiated. In this country inoculum is very rarely a limiting factor and therefore the threshold level will almost always be exceeded. -115-

Last (1963) studied the metabolism of barley leaves infected with E.zrarainis and showed that there were decreased rates of photosynthesis after an initial lag period coupled with increased respiration. However, he noted that although increasing the area of leaf inoculated progressively decreased rates of photosynthesis, the effects could not be attributed to a simple loss of leaf area. When less than 30% of a leaf was inoculated, decreases were equivalent to area losses greater than those inoculated; when more than 30% was inoculated the photosynthetic losses were equivalent to area losses less than those inoculated. This may reflect the triggering of senescence, the threshold level being less than 30% of the leaf area infected, inoculation of a greater area not accelerating the senescence rate as much as might be supposed.

It should be noted also that Last's measurements of photosynthetic rate were made 7-10 days after inoculation with E. graminis, at a time when we have shown that the level of chlorophyll in the leaf is rapidly declining, and hence lower photosynthetic rates must ensue.

Last (1963) also noted an increase in the respiration rate of infected leaves some 48 hours after inoculation as did Allen (1942). This has been found by Scott and Smillie (1963) to be linked with a change to the Hexose Monophosphate shunt pathway (HMP) in the infected leaf. -116-

The fact that this increase in respiration is evident only when photosynethesis is decreasing, together with the observation that respiration is not increased in infected etiolated leaves,- suggests that in a highly susceptible variety the decrease in photosynthesis and respiratory rise are related. Since both photosynthesis and the HMP are major metabolic sources of NADPH one possibility is that increases in respiratory activity are tied to a loss of capacity to photoreduce NADPf. This increase in respiration may lead to a further drain on the resources of the plant.

The chlorophyll work has also shown that leaves produced after the first two do not have, as high an initial level of chlorophyll. This may serve to explain the effect that early infection has on subsequent yield. Dale and Felippe (1972) have shown the importance of the first leaf to the development of the root system, and we have shown how heavy infection of these early leaves causes their premature senescence and thus could affect this development.

There remains the interesting effects of the chemical ethirimol on the growth of the plant. The structure of ethirimol is related to benzimidiazole and thus is likely to possess certain hormonal properties within the plant, one of these being the maintenance of green leaf tissue. Thus, we have a fungicide with two roles, the first the prevention of mildew infection and the second to keep the -117-

leaf tissue green. This latter'is perhaps the most important, the most notable feature of a sprayed or treated crop being the amount of green leaf tissue in comparison with an untreated crop. However, it has the advantage that it only seems to delay senescence of diseased plants not of uninfected plants. The latter could in some cases be to the detriment of the crop, if leaves were maintained green longer than the period over which they were of photosynthetic usefulness to the plant. It is perhaps this, that leads to or can lead to increases in growth particularly when the pathogen does in fact infect to quite a high degree. The chemical though not wholly preventing mildew attacks maintains the leaves green longer leading to better root development and a larger yield. Over the first period of growth we have seen this is of particular importance where plants can be treated very easily by application of the chemical to the seed.

There is another perhaps more interesting application of our studies. Do different varieties have different reactions to senescence? Do different varieties have different threshold levels at which senescence is initiated? Is this the basis, or could it become the basis for breeding for tolerance to rather than resistance to mildew attack? -118-

We have said that we consider the premature senescence initiated by mildew most important in the reduction of crop yields, this senescence being measured most critically as a reduction in chlorophyll level. Brenchley (1968) discussed the use of aerial photography in the identification and assessment of plant diseases. While Colwell (1956) investigated the identification and tracking of Puccinia striiformis infections on wheat crops in this country, and in later papers has shown that the degree of infection with various diseases can be assessed with a fair degree of accuracy from the air. The advantage being that the whole crop is sampled not just isolated plants. Aerial photography basically measures the amount of chlorophyll present in plants in the field (depending on the type of film used) and we have shown that chlorophyll content may be a sensitive pointer to the general 'health' of the crop. Thus the myriad of factors which interact and control crop yields, are automatically taken into account, in ay assessment of potential crop loss made by this means. -119-

~~SUMMARY~~

~~1) In a greenhouse experiment with Zephyr barley yield loss due to Erysiphe araminis was found to be greatest when infection occurred during stem extension.~~

~~2) Yield loss was less marked when infection occurred during tillering, but was still significant and probably due to a reduction in tiller number, possibly caused by mildew's affect on root growth.~~

~~3) Powdery mildew caused no change in the size of individual leaves and thus had no effect on the total leaf area produced per plant.~~

~~Ii) Mildew infection caused the premature initiation of senescence within the affected leaf, though this senescence did not proceed at a greater rate • than normal.~~

~~5) In a field trial with Zephyr barley mildew caused an 18% yield reduction, take-all 32% and both diseases together 34%.~~

~~6) Reduction in yield due to infection with Gaeumannomyces araminis possibly due to a reduction in the number of fertile tillers, while mildew caused a reduction in grain size. -120-~~

~~7) There was a significant reduction in the level of mildew where take-all was present, while the level of take-all was greater where mildew was present.~~

~~8) Leaf senescence was found, in greenhouse experiments, to be related to a rapid loss of chlorophyll from the tissue some 7-10 days after inoculation with E. graminis.~~

9) Ethirimol, used as a seed-dressing was shown to lead to an increase in the dry weight of both mildew infected and uninfected plants, and also an increase in the size of leaves of ethirimol treated plants.

~~10) Ethirimol, led to the maintenance of green leaf tissue in mildew infected plants. -121-~~

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~~ARCHBOLD H.K. (1942) Physiological studies in Plant Nutrition. viii Experiments with Barley on defoliation and shading of the Ear in relation to Sugar metabolism. Ann.Bot. N.S. 6 487-531~~

~~ARNON D.I. (1949) IllanIEhisiol. 24 1-15~~

~~BEBBINGTON R.M. BROOKS D.H. GEOGHEGAN M.J. & SNELL B.K. (1969) Ethirimol : a new systemic fungicide for the control of cereal powdery mildews. fh1MaIrldi p.1512~~

~~BROOKS D.H. (1972) Observations on the effect of mildew Erysiphe Laminilt on the growth of spring and winter barley. Ann.Appl.Biol. 22 149-156~~

~~BRENCHLEY G.H. (1968) Aerial photography for the study of plant diseases. Ann.FifiLt PhztsaaL.t- 6 1-22 -122-~~

~~BRUINSMA J. (1963) The quantitative analysis of chlorophylls a and b in Plant Extracts. Photochem.Photobiol. 2 241~~

~~COLWELL R.N. (1956) Determining the prevalence of certain cereal crop diseases by means of aerial photography. j-jila20La 26 223-86~~

~~DALE J.E. & FELIPPE G.M. (1972) Effects of shading the first leaf on growth of barley plants. 2. Effects on photosynthesis. Ann.Bot. 36 397-409~~

~~EDWARDS H.H. & ALLEN P.J. (1966) Distribution of the products of photosynthesis between powdery mildew and barley. Plant Physiol. 41 683-688~~

~~HOLDEN E.M. (1965) Chlorophylls Chapter 17 Pages 461-485 The Chemistry and Biochemistry of Plant Pi ments. Academic Press Editor T.W. Goodwin.~~

~~JAMES W.C. (1969) A survey of foliar diseases of spring barley in England and Wales in 1967. Ann. Appl.Biol. 3 253-63 -123-~~

~~LARGE E.C. (1954) Growth stages in Cereals. Illustration of the Feekes scale. Plant Path. 3. 128-129~~

~~LARGE E.C. & DOLING D.A. (1962) The measurement of cereal mildew and its effect on yield. Plant Path. 11 47-57~~

~~LAST F.T. (1955) Effect of powdery mildew on the yield of spring- sown barley. Plant Path. 4 22-24~~

~~LAST F.T. (1962) Analysis of the effects of Erysiphe graminis DC. on the growth of barley. Ann.Bot. N.S. 26 279-89~~

~~LAST F.T. (1963) Metabolism of barley leaves inoculated with E. graminis. Ann.Bot. N.S. 7 685-690~~

~~MACKINNEY (1941) J. Biol. Chem. 140 315 MILLERD A. & SCOTT K. (1956) Host pathogen relation in Powdery Mildew of barley. II Changes in Respiratory pattern. Aust.J.Biol. Sci. 2 37-44~~

~~PAULECH C. (1969) Influence of ErvsiDhe graminis DC..on the amount of dry substance and on the growth of vegetative organs. Biologia.Bratisl. 24 (10) 709-720~~

PORTER H.K. PAL N. & MARTIN R.V. (1950) Physiological studies in plant nutrition. XV. Assimilation of carbon by the Ear of Barley and its relation to the accumulation of dry matter in the Grain. Ann.Bot. N.S. 14 54-67

~~SCOTT K.J. & SMILLIE R.M. (1963) Possible relationship between photosynthesis (decrease) and the rise in respiration in E. graminis diseased barley leaves. Nature 192 1319-1320~~

~~THORNE G.N. (1959) Photosynthesis of lamina and sheath of barley leaves. Ann. Bot. N.S. 23 365-370 -125-~~

~~WATSON D.J. THORNE G.N. & FRENCH S.D.W. (1958) Physiological causes of differences in grain yield between varieties of barley. Ann.Bot. N.S. 22 321-352~~

~~WELBANK P.J. FRENCH S.D.W. & WITTS K.J. (1966) Dependence of yields of wheat varieties on their leaf area durations. Ann.Bot. N.S. 352 291-299 -126-~~

~~APPENDIX~~

~~-127-~~

~~APPENDIX I~~

An experiment to determine the effect of mildew at different growth stages was first set up in November 1970. It was designed to study the effect of mildew during one or more of four distinct phases in the growth of the plant, based asfollows on the Feekes scale (Large, 1954): Growth stage Infection Period Tillering 1-5 A

~~Stem Extension 6-7 B~~

~~Heading 8410 C~~

~~Grain Filling 10-11 D~~

In all there were sixteen treatments in which plants were allowed to become infected with mildew during the following growth periods:- Treatment Infection Period 1 A 2 A + B 3 A + B + C 4 A + B + D 5 A + C + D 6 A +B+C+ D 7 A + C 8 A + D 9 10 B + C 11 B + C + D 12 B + D -129-

~~Treatment Infection Period 13 14 C + D 15 16 Nil~~

~~Other-rise plants were kept free of mildew by spraying them with ethirimol as described (p 13 and below).~~

Pots (25cm diameter) of soil from the Walled Gatden at Silwood, were sown on 5 November 1970 and arranged in four randomized blocks with provision for additional pots of batley which, when inoculated would serve subsequently as sources of inoculum throughout the experiment.

The first spray of ethirimol was applied on 16 November, 11 days after sowing, to plants in treatments 9, 10, 11, 12, 13, 14, 15, 16 i.e. treatments requiring no mildew in growth period A. Two hours later all plants in the experiment were dusted with conidia of E. graminis. There were further aoplications of ethirimol to meet the requirements of the experiment as follows:

~~Date Days after sowing Applied to treatment No. 23 November 18 9, 10, 11,12,13,14,15,16 14 December 39 9,10,11,12,13,14,15,16 6 January 62 11 5,719,13,14,15,16 15 January 71 1,2,4,9,9,12,15,16 -129-~~

To allow a continuous record of growth, measurements were carried out on the main shoot of one marked plant per plot at approximately seven day intervals from 12 days after sowing (17 November) to 92 days after sowing (26 January).

~~The area, degree of mildewAmfection and senescence were recorded for each leaf onthe plant.~~

~~On 19 January (75 days after sowing several shoots were dissected to check for the presence of ears, none were in fact found. Also the mildew level was very low and a second inoculation was applied.~~

~~This second inoculation of. mildew was not successful and the plants showed signs of calcium deficiency, which was traced eventually to the soil used in the experiment.~~

~~For this reason the experiment was abandoned and repeated in its more simplified form described on page 25 . -130-~~

~~APPENDIX II~~

~~KEY TO TABLES 23 - 28~~

~~GROWTH STAGE INFECTION PERIOD~~

~~Tillering 1 - 5 A~~

~~Stem Extension 6 - 9~~

~~Grain Filling 10 - 11~~

~~ANALYSIS OF VARIANCE - SIGNIFICANCE TEVELS~~

~~Significance level~~

~~0.1%~~

~~Not significant NS TABLE 23~~

~~DRY WEIGHT OF EARS (g) FROM MARKED PLANTS IN RELATION TO MILDEW INFECTION~~

~~Infection Replicate Period I II III IV V VI VII VIII Mean~~

A 1.6654 9.1947 3.5071 2.7320 0.6027 3.8798 - 3.6977 3.1599 Lo H A-i-B 3.0725 1.6038 1.8129 - 1.5183 1.2475 3.1816 0.3817 1.6022 1 AA-B-FC 1.5831 4.5640 1.3818 - 2.0617 4.9000 1.5140 5.8156 2.7228 A+C 5.7573 9.5105 6.7181 15.1000 3.1923 - - 5.9441 5.7778 B - 3.1539 4.8776 0.2680 - 0.9336 4.8893 0.9249 1.9685 B-1-C 1.6355 4.0840 4.8825 2.0776 0.7790 0.4103 3.0813 4.0336 2.6230 C 5.1214 10.3957 5.3928 3.2462 5.3765 4.8848 5.9959 5.1142 Nil 3.0054 3.3454 11.2983 9.9952 10.5111 4.5665 9.8217 2.4314 6.8719 TABLE 24

~~TOTAL DRY WEIGHT (g) OF EARS FROM OTHER PLANTS IN.RELATION TO MILDEW INFECTION~~

~~Infection Replicate Period I IV V VI VII VIII Mean~~

A 30.6 33.9 38.1 11.3 14.4 20.5 9.0 8.1 19.4 A+B 31.6 12.0 19.1 9.3 9.o 19.4 24.5 7.5 16.4 A+B+C 20.6 22.8 16.2 7.1 22.7 13.7 23.0 29.0 19.4 A+C 20.5 42.7 40.1 24.5 14.7 18.8 10.5 36.7 26.1 B 16.0 20.6 26.9 13.5 12.1 11.2 21.2 20.1 17.7 B+C 11.1 32.5 20.9 16.3 10.5 26.1 13.7 19.9 19.9 C 29.0 45.6 19.6 14.8 32.1 34.3 35.9 21.9 29.2 Nil 35.0 28.6 62.4 40.5 25.9 29.9 65.6 9.7 37.2 -133-

~~TABLE 23 (continued)~~

~~ANOVA - DRY WEIGHT EARS FROM MARKED PLANTS~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 7 73.75 10.54 1.26 NS~~

~~Treatments 7 212.24 30.32 3.63 lE 3i~~

~~Error 49 409.90 9.36~~

~~Total 63 695.79~~

~~S.E. =1.446~~

~~TABLE 24 (continued)~~

~~ANOVA - DRY WEIGHT OF EARS FROM OTHER PLANTS~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 7 1369.36 195.62 1.90 NS~~

~~Treatments 7 2907.64 415.38 4.03 3€~~

~~Error 49 5052.44 103.11~~

~~Total 63 9329.44~~

~~S.E. = 5.078 TABLE 25~~

~~DRY WEIGHT (g) MARKED PLANTS IN RELATION TO MILDEW INFECTION~~

~~Infection Replicate Period I , II III IV V VI VII VIII Mean~~

A 3.1 7.8 5.6 5.0 4.3 7.7 4.1 7.7 5.7 A+B 5.6 3.1 4.4 1.6 5.5 4.6 4.2 6.6 4.5 A+B+C 3.3 6.o 4.2 3.7 6.1 9.8 3.4 5.9 5.3 A+C 7.1 9.1 6.6 12.6 6.1 3.7 4.3 7.3 7.1 B 2.7 5.9 4.1 1.6 2.8 4.o 5.o 2.6 3.6 B+C 6.6 4.1 6.1 3.6 6.4 4.9 3.7 7.4 5.4 6.4 10.0 4.7 5.7 7.5 4.3 6.1 3.5 6.0 Nil 3.3 3.7 10.5 8.8 10.4 4.6 9.0 5.2 6.9 -135-

~~TABLE 25 (continued)~~

~~ANOVA - DRY WEIGHT OF MARKED PLANTS~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 7 15.17 2.17 0.45 NS~~

~~Treatments 7 77.84 11.12 2.30~~

~~Error 49 237.17 4.84~~

~~Total 63 330.18~~

~~S.E. = 1.1 TABLE 26~~

~~LEAF SIZE (CM2) IN RELATION TO MILDEW INFECTION~~

~~LEAF NUMBER (1)~~

~~Infection Replicate Period III IV V VI VII VIII Mean~~

A 5.35 7.45 5.10 4.86 4.62 4.62 4.96 6.16 5.38 A+B 7.78 5.10 6.49 7.13 7.13 7.13 4.86 6.48 6.51 A+B+C 6.48 4.86 7.45 6.8o 6.43 7.13 4.86 6.90 6.36 A+C 7.78 4.86 5.35 6.48 4.96 6.8o 7.13 5.83 6.13 B 4.37 4.86 4.62 6.43 5.10 7.45 6.90 4.62 5.34 B+C 7.78 6.48 7.45 6.16 4.62 6.90 4.86 7.13 6.41 C 7.13 7.13 7.78 6.90 6.90 7.13 6.8o 7.13 7.09 Nil 7.78 5.59 7.45 7.13 5.10 7.78 4.13 7.13 6.51 TABLE 26 (continued)

~~LEAF NUMBER (2)~~

~~Infection „ Replicate Period I IV V VI VII VIII Mean~~

A 8.26 10.69 5.83 9.72 8.51 q.75 8.51 8.75 8.63 A+B 10.94 8.75 9.72 10.69 9.72 11.18 9.23 9.96 10.02 A+B+C 10.94 9.96 9.48 13.12 9.23 9.72 7.7(1 9.72 9.99 A+C 15.56 9.72 6.48 8.26 8.26 10.21 10.21 5.51 9.28 B 4.86 9.23 9.23 9.96 9.72 11.18 9.72 9.23 9.14 B+C 16.20 9.72 10.69 8.26 8.02 10.94 8.02 12.15 10.50 10.69 10.94 11.91 8.75 10.69 12.15 10.21 11.18 10.82 Nil 13.61 9.48 11.42 12.96 6.32 10.69 4.37 9.72 9.82 TABLE 26 (continued)

~~LEAF NUMBER (3)~~

~~Infection Replicate Period I II III IV V VI VII VIII Mean~~

A 14.09 19.44 13.61 18.14 13.28 17.17 16.20 15.55 15.94 A+B 17.82 15.55 3.14 18.79 16.52 18.14 16.20 17.50 16.08 A+B+C 16.20 17.50 17.17 20.09 15.56 15.88 14.58 18.47 16.93 A+C 19.12 17.50 17.50 14.90 14.90 18.14 14.14 19.14 16.79 B 11.18 17.17 17.82 17.82 14.90 19.14 19.14 16.85 16.50 B+C 19.12 17.82 19.12 12.64 14.90 19.14 15.23 19.12 17.01 C 17.50 19.79 20.09 16.85 19.44 16.85 17.50 16.52 17.94 Nil 4.86 16.52 20.09 17.50 15.88 19.12 9.48 16.20 14.96 TABLE 26 (continued)

~~LEAF NUMBER (4)~~

~~Infection Replicate Period IV V VI VII VIII Mean~~

A 19.44 29.97 25.92 27.54 18.47 27.14 25.92 26.73 25.14 A+B 27.14 24.30 28.35 24.30 21.06 28.35 27.54 27.54 26.07 uo A+B+C 14.26 26.33 25.92 28.35 23.49 23.49 23.09 26.33 23.91 ■SD A+C 29.97 28.76 29.57 26.73 24.30 22.03 27.54 25.11 26.75 B 19.44 27.54 27.54 28.35 24.30 28.35 26.73 25.92 26.02 3+C 28.76 27.14 29.97 24.30 20.41 28.35 27.54 29.16 26.95 C 25.92 29.57 31.19 27.54 29.16 25.11 27.54 26.73 27.85 Nil 28.40 28.35 29.16 25.92 25.11 29.97 23.90 25.92 27.09 TABLE 26 (continued)

~~LEAF NUMBER (5)~~

~~Infection Replicate Period IV V VI VII VIII Mean~~

A 27.54 35.48 36.94 33.05 26.33 37.91 34.99 34.02 33.28 A+B 35.48 33.05 37.42 37.91 37.91 38.88 31.59 33.05 35.66 A+BfC 31.59 36.45 35.96 35.96 34.02 34.02 26.33 36.45 33.85 A+C 38.39 35.96 38.39 29.97 3208 37.42 37.91 29.57 34.96 1 B 34.51 36.94 32.08 35.48 35.48 38.88 33.53 35.96 35.36 B+C 33.05 38.39 38.88 35.48 36.94 37.91 37.91 33.39 37.12 C 37.91 37.42 39.37 31.19 36.94 31.59 37.91 36.45 36.10 Nil 22.36 36.45 37.91 29.16 34.51 40.34 30.62 34.99 33.29 TABLE 26 (continued)

~~LEAF NUMBER (6)~~

~~Infection Replicate Period III IV V VI VII VIII Mean~~

A 34.99 32.56 41.80 37.42 33.53 40.82 39.85 38.39 37.42 A+B 39.95 36.45 38.88 37.91 41.31 39.37 35.96 35.96 38.21 A+B+C 37.91 38.88 40.92 40.82 34.02 34.51 25.52 38.88 36.42 A+C 40.82 37.91 40.82 34.51 34.02 37.91 44.71 32.00 37.84 B 32.40 35.96 32.56 38.39 37.91 41.40 37.91 40.82 37.17 B+C 40.34 43.25 44.23 40.82 41.31 37.91 41.90 41.31 41.37 C 40.34 42.28 35.96 38.39 42.77 37.42 39.85 39.37 39.55 Nil 34.99 43.25 35.43 33.53 34.99 42.77 38.88 40.82 39.08 TABLE 26 (continued)

~~LEAF NUMBER (7)~~

~~Infection Replicate Period I II III IV V VI VII VIII Mean~~

A 41.96 44.23 51.03 43.66 37.91 38.88 40.82 39.85 42.29 A+B 34.99 37.42 42.28 45.36 43.74 44.79 35.49 39.85 40.49 A+B+C 38.39 38.88 43.25 43.09 34.02 42.52 36.45 44.23 40.10 A+C 44.23 44.23 44.23 37.91 40.82 35.96 49.90 34.51 41.47 B 40.82 37.91 38.39 35.96 48.20 49.33 44.23 38.88 41.72 B+C 40.82 48.76 43.09 47.63 44.71 40.82 50.86 39.69 44.50 C 48.20 41.30 34.02 45.93 48.76 39.85 44.23 41.96 43.09 Nil 34.51 39.85 47.63 43,09 35.96 47.63 43.09 45.36 42.14 -143-

~~TABLE 26 (continued)~~

~~ANALYSIS OF VARIANCE - INDIVIDUAL LEAF SIZE~~

~~LEAF NUMBER (1)~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 7 15.6926 2.2418 2.36 €~~

~~Treatments 7 17.2503 2.4643 2.59 m~~

~~Error 49 46.6210 0.9514~~

~~Total 63 79.5639 Correction 1 2492.8800~~

~~S.E. = 0.4872~~

~~TFAF NUMBER (2)~~

~~Blocks 7 50.0259 7.1466 1.71 NS~~

~~Treatments 7 29.4899 4.2128 1.01 NS~~

~~Error 49 205.1936 4.1876~~

~~Total 63 284.7094 Correction 1 6115.0445~~

~~S.E. = 1.025 TABLE 26 (continued)~~

~~LEAF NUMBER (3) S.V. D.F. S.S. M.S. V.R. H Blocks 7 65.842 9.406 1.22 NS~~

~~Treatments 7 43.900 6.271 0.82 NS~~

~~Error 49 376.706 7.688~~

~~Total 63 486.448 Correction 1 17464.613~~

~~S.E. = 1.386~~

~~LEAF NUMBER (4)~~

~~Blocks 7 165.194 23.599 3.11 m m~~

~~Treatments 7 86.343 12.335 1.62 NS~~

~~Error 49 372.311 7.598~~

~~Total 63 623.948 Correction 1 44009.221~~

~~S.E. = 1.378 -145-~~

~~TABLE 26 (continued)~~

~~LEAF NUMBER (5)~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 7 228.157 32.593 3.29 m m~~

~~Treatments 7 107.485 15.355 1.55 NS~~

~~Error 49 486.062 9.920~~

~~Total 63 821.704 Correction 1 78186.645~~

~~S.E. = 1.575~~

~~LEAF NUMBER (6)~~

~~Blocks 7 19.664 2.809 0.21 NS~~

~~Treatments 7 134.655 19.236 1.47 NS~~

~~Error 49 641.547 13.093~~

~~Total 63 795.866 Correction 1 93671.958~~

~~S.E. = 1.809 -146-~~

~~TABLE 26 (continued)~~

~~LEAF NUMBER (7)~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 7 61.229 8.747 0.39 NS~~

~~Treatments 7 110.176 15.739 0.71 NS~~

~~Error 49 1090.302 22.251~~

~~Total 63 1261.707 Correction 1 11276+.998~~

~~S.E. = 2.359 TABLE 27~~

~~TOTAL LEAF AREA PRODUCED (CM2) IN RELATION TO MILDEW INFECTION (Fifty seven days after sowing)~~

~~Infection Replicate Period IV V VI VII VIII Mean~~

A 141.63 264.87 261.98 265.11 239.04 220.08 215.94 215.38 227.99 A+B 221.01 248.51 244.74 224.62 268.67 272.89 247.05 256.53 248.12 A+B+C 244.97 255.07 268.42 272.59 237.90 258.55 220.18 220.00 247.20 A+C 279.79 266.93 269.09 244.95 247.12 211.00 276.59 189.79 243.16 B 227.45 251+.66 243.08 172.100 270.30 272.01 264.38 249.96 244.29 B+C 275.66 275.47 277.91 221.78 274.11 190.77 185.82 196.95 236.06 C 273.87 263.26 180.32 216.84 285.28 246.65 226.00 271.20 245.43 Nil 170.81 255.47 274.71 258.47 246.32 285.61 196.43 272.57 245.05 TABLE 27 (continued)

~~ANOVA - TOTAL LEAF AREA PRODUCED PER PLANT (57 days after sowing)~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 7 9584.9 1369.271 1.21 NS~~

~~Treatments 7 3278.6 468.371 0.41 NS~~

~~Error 49 55664.2 1136.004~~

~~Total 63 68527.7 Correction 1 3772019.4~~

~~S.E. = 16.85 TABLE 28~~

~~GREEN LEAF AREA (CM2 ) IN RELATION TO MILDEW INFECTION (Fifty seven days after sowing)~~

~~Infection Replicate Period I II III IV V VI VII VIII Mean~~

A 135.11 201.26 173.27 201.01 204.26 158.61 173.60 156.49 175.45 A+B 154.50 130.68 90.47 65.92 144.75 154.89 121.79 85.24 118.53 A+B+C 127.37 138.59 110.65 167.34 132.11 143.93 102.35 82.01 126.17 A+C 177.97 200.14 188.96 171.87 209.95 146.13 198.62 159.89 181.69 B 128.79 104.01 115.39 - 138.07 144.69 159.98 126.77 114.71 B+C 160.67 131.29 116.33 112.15 173.89 - 87.42 C 241.39 173.89 52.00 149.10 208.01 175.90 184.61 242.53 178.42 Nil 110.57 191.52 187.64 165.80 235.67 209.74 135.35 204.85 180.14 -150-

~~TABLE 28 (continued)~~

~~ANOVA - GREEN LEAF AREA PER PLANT (57 days after sowing)~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 7 19119.9 2731.414 1.38 NS~~

Treatments 7 79309.5 11329.929 5.74 m * *

~~Error 49 96731.6 1974.114~~

~~Total 63 195161.01 Correction 1 1351502.15~~

~~S.E. = 22.21 -151-~~

~~KEY TO TABLES 29 - 1+8~~

~~G.S. Do No drought~~

~~Dl Drought during tillering 1-5~~

~~D2 Drought during stem extension 6-9~~

~~D3 Drought during grain filling 10-11~~

~~0 Control~~

~~M Mildew only~~

~~T Take-all only~~

~~T 8c M Take-all and mildew TABLE 29 Field Experiment 1971~~

~~GRAIN YIELD PER PLOT (Kg) (Corrected for moisture content)~~

~~Treatments Blocks II III IV Mean Do 0 2.39 2.42 1.94 2.25 Do M 1.59 1.76 2.04 1.79 Do T 1.13 1.41 1.48 1.34 Do T & M 1.30 0.97 1.52 1.26~~

~~D1 0 1.45 2.89 2.24 2.19 D1 M 1.32 1.14 1.68 1.38 Dl T 0.97 1.54 1.13 1.21 D1 T & M 1.10 0.66 1.42 1.06~~

~~,D2 0 1.54 2.20 2.13 1.95 D2 M 1.54 1.76 1.83 1.71 D2 T 0.96 1.54 1.52 1.34 D2 T & M 1.23 1.76 1.57 1.52~~

D3 0 0.45 2.02 1.57 1.34 D3 M 1.11 1.98 1.31 1.46 D3 T 1.11 1.78 1.19 1.36 D3 T & M 1.11 1.65 0.96 1.24 Anova grain yield S.V. D.F. S.S. M.S. V.R. Blocks 2 1.723 0.8615 5.098 NS Drought 3 0.765 0.255 1.509 NS Plot Error 6 1.017 0.169 Treatments 3 3.395 1.132 11.79 KIM Bi x Tr 6 0.55 0.141 1.47 NS Dr x Tr 9 1.47 0.163 1.70 NS Bl x Dr x Tr 19 1.46 0.091 0.84 NS Total 47 10.69 Correction ,' 1 111.965 Sub Plot Error 24 2.31 0.096 -153-

~~TABLE 30 Field Experiment 1971~~

~~NUMBER OF SHOOTS PER PLOT~~

~~Treatments Blocks II III IV Mean Do 0 1806 1899 2171 1958 Do M 1460 1516 2816 1931 Do T 970 1032 123 5 1079 Do T & m 1036 786 1910 1245~~

~~Dl 0 1281 2411 1821 1838 D1 M 1391 1032 1929 1451 D1 T 829 1098 867 932 D1 T & M 965 731 1296 997.~~

~~D2 0 1023 1845 1478 1448 D2 M 1450 1630 1673 1584' D2 T 706 1111 1207 1008 D2 T & M 1149 1716 1531 146 5~~

D3 0 663 1694 1532 1293 D3 m 1544 2185 1226 16 52 D3 T 1028 1463 941 1144 D3 T & M 1168 1471 949 1196 Anova shoot number S.V. D.F. S.S. M.S. V.R. Blocks 2 1349036 674518 2.37 NS Drought 3 465489 155163 0.54 NS Plot Error 6 1709451 284908 Treatments 3 3345937 1115312 12.01 KMM B1 x Tr 6 759237 126539 1.36 NS Dr x Tr 9 1202320 133591 1.44 NS Bl x Dr x Tr 18 1469864 81603 0.98 NS Total 47 10300336 Correction 1 92 583740 Sub Plot Error 24 2228101 92837 TABLE 31 Field Experiment 1971 MEAN EAR DRY WEIGHT (g) IN RELATION TO DROUGHT AND DISEASE

~~Treatments Days after sowing 78 93 108 0 0.3433 0.9409 1.1579 M o.3044 0.8496 0.9955 T 0.3495 1.0134 1.2643 T & M 0.3155 0.9634 1.0522~~

~~Do 0.3133 0.9403 1.1234 D1 0.3671 1.0026 1.1247 D2 0.3415 0.9600 1.1919 D3 0.2906 0.8644 1.0199 -155-~~

~~TABLE 32 Field Experiment 1971~~

~~MEAN EAR DRY WEIGHT (93 days after sowing)~~

~~Treatments Blocks II III IV Mean Do 0 1.1850 0.9591 0.9372 1.0270 Do M o.7734 0.6376 0.8795 0.7631 Do T 0.9739 1.0752 0.9149 0.9896 Do T & M 1.0842 0.9282 0.9318 0.9313~~

~~D1 0 1.0040 0.8743 0.9369 0.9383 D1 M 1.1014 0.9427 0.9653 1.0031 D1 T 1.1598 1.0302 1.1497 1.1132 D1 T & M 0.9135 0.8384 1.0660 0.9559~~

~~D2 0 1.1294 1.0236 1.0076 1.0299 D2 M 0.7971 0.8333 0.3113 0.3139 D2 T 1.0850 0.7590 0.9337 0.9275 D2 T & M 1.0739 1.1875 0.9446 1.0686~~

D3 0 0.5776 0.8908 0.9375 0.'7686 D3 M 1.7298 0.8932 0.8317 1.1515 D3 T 0.9858 0.9470 1.1369 1.0232 D3 T & M 0.8045 0.6563 0.8829 0.8479 Anova Ear weight 93 days after sowing S.V. D.F. S.S. M.S. V.R. Blocks 2 0.0924 0.0462 14.90 NH Drought 3 0.0278 0.0093 3.00 NS Plot Error 6 0.0185 0.0031 Treatments 3 0.0444 0.0148 0.50 NS Bl x Tr 6 0.1074 0.0179 0.60 NS Dr x Tr 9 0.5367 0.0596 2.01 NS Bl x Dr x Tr 18 0.6046 0.0336 1.13 NS Total 47 1.4318 Correction 1 44.6238 Sub Plot Error 24 0.7120 0.0297 -156-

~~TABLE 33 Field Experiment 1971 MEAN EAR DRY WEIGHT. (108 days after sowing)~~

~~Treatments Blocks TI III IV Mean Do 0 1.3237 1.2743 0.9936 1.1639 Do M 1.0893 1.1607 0.7243 0.9914 Do T 1.1655 1.3666 1.1984 1.2435 Do T & M 1.2553 1.2334 0.7959 1.0949~~

~~D1 0 1.1321 1.1989 1.2298 1.1869 D1 M 0.9486 1.1045 0.8707 0.9746 D1 T 1.1694 1.4024 1.3032 1.2917 D1 T & M 1.1386 0.9023 1.0960 1.0456~~

~~D2 0 1.5059 1.1923 1.4415 1.3799 D2 M 1.0619 1.0800 1.0936 1.0795 D2 T 1.3592 1.3866 1.2594 1.3351 D2 T & M 1.0708 1.0259 1.0252 1.0406~~

D3 0 0.6782 1.1995 1.0251 0.9676 D3 M 0.7185 0.9062 1.0681 0.9976 D3 T 1.0799 1.2165 1.2643 1.1969 D3 T & M 0.9501 1.1218 1.0112 1.0277 Anova Ear dry weight 108 days after sowing S.V. D.F. S.S. . M.S. V.R. Blocks 2 0.0787 0.0394 0.61 NS Drought 3 0.2146 0.0715 1.11 NS Plot Error 6 0.3978 0.0646 Treatments 3 0.5577 0.1859 14.64 xxii Bl x Tr 6 0.0451 0.0075 0.59 NS Dr x Tr 9 0.1351 0.0150 1.18 NS Bl x Dr x Tr 18 0.260 0.0144 1.13 NS Total 47 1.6790 Correction 1 60.1198 Sub Plot Error 24 0.3051 0.0127 -157-

~~TABLE 34 Field Experiment 1971~~

~~SIEVING TEST DATA~~

~~Treatment mean % grain in each sieve Top Middle Bottom 2.9mm 2.5mm 2.2mm 2.2mm Do 0 25.10 35.80 19.23 16.81 Do M 16.64 37.60 26.55 19.21 Do T 19.87 39.00 26.75 14.38 Do T & M 16.12 32.97 29.67 21.24~~

~~D1 0 19.08 37.35 25.10 18.47 Dl M 13.95 39.20 28.90 17.95 Dl T 22.03 32.14 26.00 19.93 D1 T & M 14.10 35.00 32.00 18.90~~

~~D2 0 21.30 34.15 23.00 21.55 D2 M 15.20 36.64 27.10 21.06 D2 T 19.10 31.33 26.60 22.97 D2 T & M 12.56 30.80 30.40 26.24~~

~~D3 0 17.47 34.47 28.55 19.51 D3 m 10.93 37.00 31.55 20.52 D3 T 17.00 33.65 29.00 20.35 D3 T & M 13.95 33.50 30.60 21.95~~

~~Do 15.40 36.34 25.56 22.70 Dl 17.29 35.92 28.00 18.79 D2 17.04 33.23 26.78 22.95 D3 14.84 34.66 29.93 20.57~~

~~0 20.74 35.44 23.97 19.85 M 14.18 37.61 28.53 19.68 T 19.50 34.03 27.09 19.38 -158-~~

~~TABLE 35 Field Experiment 1971~~

~~TRANSFORMED DATA % GRAIN SAMPLE IN LARGE SIEVE~~

~~Treatments Blocks II III IV Do 0 27.63 31.37 31.11 Do M 23.42 25.10 23.73 Do T 23.34 31.50 24.04 Do T & M 21.72 24.35 24.88~~

~~Dl 0 21.97 27.42 27.97 D1 M 21.47 23.11 21.22 D1 T 20.44 33.34 29.13 D1 T & M 13.24 21.30 26.06~~

~~D2 0 29.67 24.95 27.69 D2 M 21.47 19.55 27.28 D2 T 24.80 24.27 28.52 D2 T & m 19.73 19.28 23.11~~

D3 0 12.25 31.24 27.28 D3 M 10.94 21.97 22.95 D3 T 16.85 25.55 29.40 D3 T & M 17.46 19.00 28.18 Anova transformed data S.V. D.P. S.S. M.S. V.R. Blocks 2 288.51 144.26 3.80 NS Drought 3 101.56 33.85 0.89 NS Plot Error 6 227.87 37.98 Treatments '3 238.72 79.57 10.32 RHM Bl.x Tr 6 53.01 8.83 1.15 NS Dr x Tr 9 43.72 5.41 0.70 NS Bl x Dr x Tr 18 131.96 /7.33 0.95 NS Total 47 1090.35 Correction 1 27900.57 Sub Plot Error 24 184.97 7.71 TABLE 36 Field Experiment 1971

~~MEAN TOTAL SHOOT DRY WEIGHT (g,)' IN RELATION TO DROUGHT AND DISEASE.~~

~~Treatments Days after sowing 36 5o 64 78 93~~

~~0 0.1870 0.5893 1.0915 1.5961 2.0297 M 0.1951 0.5496 1.0094 1.3721 1.7794 T 0.1643 0.5399 1.0546 1.5540 2.0869 T & M 0.1707 0.5460 0.9781 1.3736 1.9497~~

~~Do 0.1844 0.5754 1.0294 1.4791 2.0307 Dl 0.1986 0.5440 1.0275 1.4430 1.9790 D2 0.1744 0.5593 1.0419 1.5515 1.9463 D3 0.1690 0.5476 1.0347 1.4221 1.8909 -160-~~

~~TABLE 37 Field Experiment 1971~~

~~MEAN TOTAL SHOOT WEIGHT (93 days after sowing)~~

~~Treatments Blocks II III IV Mean Do 0 2.4730 2.0843 2.1999 2.2523 Do M 1.7245 1.3207 1.9576 1.6676 Do T 1.9499 2.2951 2.0881 2.1110 Do T & M 2.2575 1.9663 2.0518 2.0918~~

~~D1 0 2.0947 1.9490 1.9963 1.9799 D1 M 2.1607 1.8245 1.9637 1.9494 Dl T 2.1987 2.1078 2.1587 2.1550 D1 T & M 1.6839 1.7212 2.0777 1.8275~~

~~D2 0 2.2407 2.1574 2.2398 2.0981 D2 M 1.6636 1.6447 1.9128 1.7403 D2 T 2.1010 1.5909 1.8734 1.8551 D2 T & M 2.0680 2.2699 1.9374 2.0917~~

D3 0 1.5047 2.0512 1.8099 1.7886 D3 M 1.4150 1.9531 1.9130 1.7603 D3 T 2.1806 2.0410 2.4588 2.2267 D3 T & M 1.7325 1.7206 1.9106 1.7878 Anova total shoot weight 93 days after sowing S.V. D.F. S.S. M.S. V.R. Blocks 2 0.0855 0.04275 0.95 NS Drought 3 0.1203 0.0401 0.90 NS Plot Error 6 0.2688 0.0448 Treatments 3 0.6984 0.2328 6.18 xm B1 x Tr 6 0.0911 0.0135 0.36 NS Dr x TR 9 0.9109 0.1012 2.69 € Bl x Dr x Tr 18 0.8235 0.0458 1.21 NS Total 47 2.9895 Correction 1 186.0319 Sub Plot Error 24 0.9046 0.0377 -161-

TABLE 38 Field Experiment 1971 MEAN INDIVIDUAL LEAF AREAS IN RELATION TO DROUGHT AND DISEASE. LEAF (1) Treatments Blocks II III IV Mean Do 0 4.45 4.79 4.62 4.62 Do M 4.82 4.23 4.65 4.57 Do T 4.45 4.65 4.56 4.55 Do T & M 4.97 4.35 4.69 4.67

~~Dl 0 4.31 4.88 5.48 4.89 D1 M 4.91 4.66 4.77 4.78 Dl T 4.27 4.42 5.05 4.58 D1 T & M 4.53 4.44 4.54 4.50~~

~~D2 0 4.33 4.62 4.65 4.53 D2 M 4.72 4.38 4.97 4.69 D2 T 4.03 4.85 4.82 4.57 D2 T & M 5.46 4.38 4.32 4.72~~

D3 0 4.33 5.08 4.35 4.59 D3 M 4.83 4.54 4.58 4.65 D3 T 3.78 4.67 4.73 4.39 D3 T & M 4.72 4.29 4.31 4.44 Anova Leaf 1 S.V. D.F. S.S. M.S. V.R. Blocks 2 0.17 0.087 1.05 NS Drought 3 0.18 0.060 0.72 NS Plot Error 6 0.50 0.083 Treatments 0.17 0.057 0.41 NS Bl x Tr g 2.35 0.391 2.80 H Dr x Tr 9 0.35 0.039 0.28 NS B1 x Dr x Tr 18 1.09 0.061 0.43 NS Total 47 4.81 Correction 1 1019.64 Sub Plot Error 24 3.10+ 0.14 -162-

~~TABLE 38 (continued) LEAF (2) Treatments Blocks II III IV Mean Do 0 7.25 7.18 7.76 7.38 Do M 6.97 6.95 8.21 7.37 Do T 7.99 8.07 8.36 8.14 Do T & M 7.35 7.13 7.93 7.47~~

~~D1 0 7.29 9.15 8.74 8.39 D1 M 7.29 7.4o 7.99 7.56 D1 T 6.71 7.94 8.51 7.39 Dl T & M 7.47 7,19 8.33 7.66~~

~~D2 0 6.73 7.16 7.54 7.14 D2 M 6.97 8.13 8.54 7.88 D2 T 5.82 7.93 7.23 6.99 D2 T & M 7.00 6.98 6.61 6.86~~

D3 0 6.73 9.64 7.62 8.00 D3 M 7.62 9.05 8.21 8.29- D3 T 6.31 7.85 8.13 7.43 D3 T & M 8.85 8.02 7.75 8.21 Anova Leaf 2 S.V. D.F. S.S. M.S. V.R. Blocks 2 6.35 3.18 5.88 A Drought 3 3.98 1.33 2.46 NS Plot Error 6 3.21 0.54 Treatments 0.46 0.15 0.41 NS Bl X Tr 6 4.10 0.68 1.84 NS Dr x Tr 9 5.24 0.58 1.60 NS B1 x Dr x Tr 18 4.71 0.26 0,.:70W NS Total 47 28.05 Correction 1 2814.90 Sub Plot Error 24 8.81 0.37 -163-

~~TABLE 38 (continued) LEAF (3)~~

~~Treatments Blocks II III IV Mean Do 0 11.61 11.79 11.85 11.75 Do M 10.47 10.48 12.93 11.29 Do T 10.80 11.01 10.25 10.69 Do T & M 10.98 10.99 11.36 11.11~~

~~Dl 0 10.74 13.71 12.58 12.34 Dl M 9.98 11.63 13.95 11.35 Dl T 9.88 10.77 11.65 10.77 Dl T & M 11.39 10.95 11.1+9 11.28~~

~~D2 0 10.04 11.54 10.88 10.82 D2 M 11.43 11.86 12.29 11.86 D2 T 8.70 11.49 12.01+ 10.74 D2 T & M 10.94 11.07 10.96 10.99~~

D3 0 10.65 12.73 12.04 11.81 D3 M 12.42 14.03 11.86 12.77 D3 T , 3.81 12.30 11.95 11.02 D3 T & M 12.49 12.44 11.58 12.17 Anova Leaf 3 S.V. D.F. S.S. M.S. V.R. Blocks 2 13.37 6.68 7.03 m Drought 3 5.18 1.73 1.82 NS Plot Error 6 5.67 0.95 Treatments 8.62 2.87 3.41 € Bi x Tr g 7.63 1.27 1.51 NS Dr x Tr 9 4.56 0.51 0.61 NS Bi x Dr x Tr 18 12.58 0.70 0.83 NS Total 47 57.61 Correction 1 6297.04 Sub Plot Error 24 20.21 04'84 -164-

~~TABLE 38 (continued) LEAF (4)~~

~~Treatments Blocks II III IV Mean Do 0 16.48 i4.4o 17.65 16.18 Do M 19.15 19.57 15.74 17.82 Do T 16.11 10.72 11.25 12.69 Do T & M 16.86 17.79 12.61 15.79~~

~~Dl 0 15.95 21.53 22110 19.83 D1 M 15.25 16.13 16.53 15.99 D1 T 14.19 15.10 15.25 14.85 D1 T & M 12.56 12.04 12.39 12.33~~

~~D2 0 21.63 19.31 13.22 18.05 D2 M 17.84 15.29 16.70 16.61 D2 T 13.74 15.72 14.80 14.75 D2 T & M 14.25 15.02 15.62 14.63~~

D3 0 14.83 21.91 13.70 16.81 03 M 13.66 20.77 18.53 17.65 D3 T 15.21 16.70 17.91 16.61 D3 T & M 15.84 23.45 15.52 18.27 Anova leaf 4 S.V. D.F. S.S. M.S. V.R. Blocks 2 25.29 12.64 0.97 NS Drought 3 22.21 7.40 0.57 NS Plot Error 6 77.88 12.98 Treatments 3 70.89 23.63 4.64 x Bl xTr 6 16.03 2.67 0.52 NS Dr x Tr 9 84.76 9.42 1.85 NS B1 x Dr x Tr 18 106.11 5.90 1.16 NS Total 47 403.16 Correction 1 12593.56 Sub Plot Error 24 122.14 5.09 -165-

~~TABLE 38 (continued)~~

~~LEAF (5) Treatments Blocks II III IV Mean Do 0 26.89 25.28 27.84 26.67 Do M 20.77 26.33 24.92 24.00 Do T 24.82 16.20 28.37 23.13 Do T & M 25.31 23.88 17.65 22.28~~

~~Dl 0 21.04 29.75 25.49 25.42 D1 M 18.56 17.30 21.37 19.08 D1 T 18.39 19.19 21.37 19.65 D1 T & M 18.54 13.39 17.31 16.41~~

~~D2 0 16.82 26.76 20.85 21.48 D2 M 25.02 20.11 23.92 23.02 D2 T 22.46 23.81 22.67 22.98 D2 T & M 22.91 17.08 20.07 20.02~~

D3 0 25.24 28.64 21.83 25.24 D3 M 23.55 25.88 20.17 23.20 D3 T 22.65 26.21 24.26 24.37 D3 T & M 27.34 23.04 21.98 24.12 Anova leaf 5 S.V. D.F. S.S. M.S., V.R. Blocks 2 0.29 0.15 0.02 NS Drought 3 135.04 45.01 5.51 N Plot Error 6 49.02 8.17 Treatments 3 96.89 32.30 2.66 NS Bl x Tr 6 120.39 20.06 1.65 NS Dr x Tr 9 89.95 10.00 0.82 NS B1 x Dr x Tr 18 171.19 9.51 0.78 NS Total 47 662.77 Correction 1 24445.57 Sub Plot Error 24 291.58 12.15 -166-

~~TABLE 38 (continued) LEAF (6)~~

~~Treatments Blocks II III IV Mean Do 0 33.03 31.71 35.01 33.25 Do M 18.62 32.61 32.21 27.81 Do T 22.92 27.34 30.78 27.01 Do T & M 29.50 28.86 29.97 29.44~~

~~Dl 0 22.79 34.25 27.84 28.29 D1 M 22.36 19.12 27.22 22.90 D1 T 15.72 24.88 26.90 22.50 D1 T & M 20.23 16.17 24.08 20.16~~

~~D2 0 17.79 29.91 29.96 25.89 D2 M 29.58 26.87 28.35 28.27 D2 T 23.17 25.30 26.77 25.08 D2 T & M 27.00 76.29 30.43 27.91~~

• D3 0 32.36 35.44 30.55 32.78 D3 M 27.32 34.80 27.11 29.74 D3 T 22.22 34.81 29.39 28.80 D3 T & M 20.55 29.28 29.89 26.57 Anova leaf 6 S.V. D.F. S.S. M.S. V.R. Blocks 2 248.77 124.39 10.33 A Drought 3 288.57 96.19 8.00 € Plot Error 6 72.20 12.03 Treatments 3 135698 45.33 3.13 w B1 ,x Tr 6 61.62 10.27 0.71 NS Dr x Tr 9 120.74 13.42 0.93 NS B1 x Dr x Tr 18 286.30 15.91 1.10 NS Total 47 1214.18 Correction 1 35711.70 Sub Plot Error 24 347.92 -167-

~~TABLE 38 (continued)~~

~~LEAF (7) Treatments Blocks SI III IV Mean Do 0 31.06 34.56 33.61 33.08 Do M 34.53 25.41 33.91 31.28 Do T 30.79 27.47 29.58 29.28 Do T & M 32.98 32.66 30.94 32.19~~

~~D1 0 19.74 29.79 28.07 25.87 D1 M 27.70 26.54 28.76 27.67 D1 T 18.20 30.27 26.48 24.98 D1 T & M 20.86 21.79 25.89 22.85~~

~~D2 0 34.61 31.30 34.86 33.59 D2 M 28.39 29.65 33.29 30.44 D2 T 34.21 30.72 30.25 31.73 D2 T & M 28.29 28.80 30.77 29.29~~

D3 0 27.53 38.53 32.83 32.96 D3 M 29.26 37.15 33.05 33.15 D3 T 31.50 34.89 35.26 33.88 D3 T & M 28.53 31.46 33.64 31.21 Anova leaf 7 S.V. D.F. S.S. M.S. V.R. Blocks 2 63.13 31.56 1.50 NS Drought 3 397.12 132.37 6.30 x Plot Error 6 126.11 21.02 Treatments 40.24 13.41 1.83 NS Bl x Tr 2 39.39 6.57 0.90 NS Dr x Tr 9 61.86 6.87 0.94 NS Bl x Dr x Tr. 18 135.73 7.54 1.03 NS Total 47 863.58 Correction 1 43823.84 Sub Plot Error 24 175.12 7.30 -168-

~~TABLE 38 (continued)~~

~~LEAF (8) Treatments Blocks II III IV Mean Do 0 26.80 28.80 31.07 28.89 Do M 34.77 22.58 30.38 29.24 Do T 27.24 22.47 26.88 25.53 Do T & M 31.45 30.06 28.01 29.84~~

~~Dl 0 15.37 25.99 25.86 22.41 Dl M 20.46 22.12 22.99 21.86 Dl T 12.78 24.75 23.65 20.39 Dl T & M 15.12 17.71 20.52 17.78~~

~~D2 0 30.70 29.56 36.09 32.12 D2 M 25.52 25.00 30.61 27.04 D2 I 30.49 27.61 25.58 27.89 D2 T & M 25.05 22.24 28.32 25.20~~

D3 0 26.35 33.16 30.29 29.93 D3 M 23.72 34.21 30.54 29.49 D3 T 24.63 29.46 30.16 28.08 D3 T & M 23.56 30.52 29.43 27.84 Anova leaf 8 S.V. D.F. S.S. M.S. V.R. Blocks 2 99.98 49.99 0.98 NS Drought 3 553.32 194.44 3.61 NS Plot Error 6 306.76 51.13 Treatments 3 76.41 25.47 7.74 H** Bl x Tr 6 29.92 5.00 1.52 ns Dr x Tr 9 82.46 9.16 2.78 R Bl x Dr x Tr 18 48.98 2.72 0.83 NS Total 47 1197.83 Correction 1 33635.1+3 Sub Plot Error 24 78.90 3.29 -169-

~~TAELE 38 (continued)~~

~~LEAF (9) (Flag Leaf)~~

~~Treatments Blocks Mean Do 0 8.72 10.29 11.34 10.12 Do M 14.72 9.36 12.64 12.24 Do T 10.08 7.69 8.07 8.61 Do T & M 13.54 11.04 9.96 11.51~~

~~D1 0 4.55 9.26 9.62 7.47 D1 M 6.62 6.36 9.92 6.63 D1 T 4.19 8.17 8.22 6.86 D1 T & M 4.10 5.30 6.12 5.17~~

~~D2 0 11.81 11.45 14.81 12.69 D2 M 9-35 8.07 12.79 10.07 D2 T 12.31 10.99 9.35 10.88 D2, T & M 8.79 6.67 11.34 8.93~~

D3 0 10.48 13.24 10.95 11.56 D3 M 7.84 15.35 11.80 11.66 D3 T 7.69 12.19 9.92 9.93 D3 T & m 8.42 12 01 9.55 9.99 Anova leaf 9 S.V. D.F. S.S. M.S. V.R. Blocks 2 12.40 6.20 0.52 NS Drought 3 155.0o 51.33 4.28 NS Plot Error 6 71.90 11.98 Treatments 3 21.58 7.19 3.24 x B1 x Tr 6 11.16 1.86 0.84 NS Dr x Tr 9 40.80 4.53 2.0+ NS Bl x Dr x Tr 18 42.14 2.34 1.05 NS Total 47 354.98 Correction 1 4466.99 Sub Plot Error 24 53.30 -170-

~~TABLE 39 Field Experiment 1971~~

~~MEAN LEAF AREA PRODUCED PER PLANT IN RELATION TO DROUGHT PERIOD AND DISEASE.~~

~~Treatments Days after sowing 36 50 64 78 Do 0 44.90 116.11 159.02 159.02 Do M 45.95 112.35 163.83 163.83 Do T 38.92 100.29 145.28 145.29 Do T & M 42.17 109.25 160.88 160.88~~

~~D1 o 53.35 115.31 148.01 148.01 Dl M 51.45 98.95 139.26 139.26 D1 T 46.65 94.20 128.82 128.82 Dl T & M 40.30 83.55 117.73 117.73~~

~~D2 0 44.32 102.47 171.05 171.05 D2 M 50.63 104.53 157.34 157.31+ D2 T 40.43 97.83 151.58 151.58 D2 T & M 41.77 102.64 148.05 148.05~~

~~D3 0 42.87 113.77 163,49 163.49 D3 M 47.51 111.46 168.55 168,55 D3 T 38.70 101.59 159.93 159.93 D3 T & M 43.86 105.40 161.62 161.62~~

~~Do 42.99 109.50 157.25 157.25 D1 47.94 98.00 133.46 133.46 D2 301.30 101.87 157.01 157.01 D3 43.24 108.05 163.40 163.40~~

~~0 46.36 111.92 160.39 160.39 M 48.90 106.82 157.25 157.25 T 41.18 98.48 146.40 146.40 T & M 42.03 100.21 147.07 147.07 Drought Drought Drought Phase Phase Phase 1 2 3 -171-~~

~~TABLE 4o Field Experiment 1971 MEAN LEAF AREA PRODUCED PER PLANT (78 days after sowing) IN RELATION TO DROUGHT PERIOD AND DISEASE.~~

~~Treatments Blocks II III IV Mean~~

~~Dd 0 146.76 159.50 170.81 159.02 Do M 174.52 147.04 169.94 163.83 Do T 154.56 134.29 146.99 145.28 Do T & M 167.96 164.10 150.59 160.88~~

~~D1 0 116.79 167.42 159.82 148.01 D1 M 134.42 133.36 150.01 139.26 D1 T 99.86 145.54 141.07 129.82 D1 T & M 113.40 111.50 128.28 117.73~~

~~D2 0 191.29 165.31 166.55 171.05 D2 M 157.95 144.62 169.46 157.31+ D2 T 159.49 153.43 141.83 151.58 D2 T & M 148.56 137.15 158.44 148.05~~

D3 0 150.79 185.69 153.99 163.49 D3 M 150.22 191.06 164138 168.55 D3 T 144.76 165.16 169.96 159.93 D3 T & M 155.30 168.16 161.40 161.62 Anova leaf area produced 78 days after sowing S.V. D.F. S.S. M.S. Blocks 2 751.42 375.71 0.72 NS Drought 3 6233.46 2096.15 4.03 NS Plot Error 6 3120.72 520.12 Treatments 3 1914.46 604.82 4.49 H Bl x Tr 6 675.80 112.63 0.83 NS Dr x Tr 9 1383.89 153.77 1.14 NS Bl x Dr x Tr 18 2551.91 141.77 1.05 NS Total 47 16586.66 Correction 1 1120381.57 Sub Plot Error 24 3227.71 134.49 -172-

~~TABLE 41 Field Experiment 1971~~

~~MEAN GREEN LEAF AREA (CM2) PER PLANT IN RELATION TO DROUGHT PERIOD AND DISEASE~~

~~Treatments Days after sowing 36 50 64 78 Do 0 44.90 104.42 98.13 54.06 Do M 45.95 80.57 76.85 23.82 Do T 38.92 85.28 84.58 29.59 Do T & M 42.12 79.61 76.55 29.75~~

~~D10 53.09' 95.94 90.32 39.58 D1 M 51.45 75.71 76.15 24.36 D1 T 46.4o 78.15 81.37 27.37 Dl T & M 40.13 58.45 52.92 17.11~~

~~D2 0 40.97 89.12 100.73 48.48 D2 M 50.66 75.94 70.61 23.37 D2 T 40.41 93.02 94.37 39.51 D2 T & M 41.77 73.24 65.60 22.65~~

~~D3 0 42.84 94.75 101.34 41.21 D3 m 47.50 77.63 79.04 22.92 D3 T 39.54 83.96 102.55 35.78 D3 T & M 43.65 73.25 70.38 18.89~~

Do 42.98 87.47 84.03 34.30 D1 47.77 77.06 75.19 27.10 D2 44.28 90.33 82.83 33.5o D3 43.13 92.40 88.33 29.70 o 46.28 96.06 97.63 45.83 M 48.89 77.46 75.66 23,62 T 41.07 82.60 90.72 33.06 T & M 41.93 71.14 66.36 22.10 Drought Drought Drought Phase Phase Phase 1 2 3 -173-

~~TABLE 42 Field Experiment 1971~~

MEAN GREEN LEAF AREA (CM2) PER PLANT IN RELATION TO DROUGHT PERIOD AND DISEASE ( 78 days after sowing) Treatments Blocks II III IV Mean Do 0 53.28 49.92 58.97 54.06 Do M 26.61 16.49 28.35 23.82 Do T 28.07 17.4o 43.29 29.59 Do T & M 33.4o 24.47 31.39 29.75

~~D1 0 10.59 48.31 59.83 39.58 D1 M 17.48 22.92 32.68 24.36 D1 T 9.99 45.31 26.90 27.37 D1 T & M 11.26 17.84 22.23 17.11~~

~~D2 0 43.73 45.91 55.80 48.48 D2 M 24.53 13.97 31.62 23.37 D212 37.95 41.45 39.14 39.51 D2 T & M 18.49 15.88 33.55 22.64~~

D3 0 5.93 65.57 52.14 41.21 D3 M 10.05 29.59 29.13 22.92 D3 T 15.11 42.99 419.25 35.78 D3 T & M 14.75 21.24 20.69 18.89 Anova mean green leaf area 78 days after sowing S.V. D.F. S.S. M.S. V.R. Blocks 2 2052.95 1026.43 3.24 NS Drought 3 406.06 203.03 0.64 NS Plot Error 6 1902.57 317.10 Treatments 3 4292.98 1430.99 17.12 m3ix Bl x Tr 6 888.23 149.04 1.77 NS Dr x Tr 565.46 62.83 0.75 NS Bl x Dr x Tr 18 1118.16 62.12 0.74 NS Total 47 11226.41 Correction 1 46585.45 Sub Plot Error 24 2006.39 83.60 -174-

TABLE 43 Field Experiment 1971 SENESCENCE PER PLANT IN RELATION TO DROUGHT PERIOD AND DISEASE. Treatments Days after sowing 36 50 64 78 Do 0 - 10.07 38.29 66.01 Do M - 28.28 53.09 85.46 Do T 0.02 14.97 41.78 79.63 Do T & M 0.04 27.13 52.42 81.51

~~D1 0 0.48 16.80 38.97 73.26 Dl M - 23.49 45.32 82.51 Dl T 0.52 17.04 36.84 78.76 Dl T & M 0.44 30.05 55.05 85.47~~

~~D2 0 0.05 13.03 41.11 71.66 D2 M 0.02 27.35 55.12 85.15 D2 T 0.05 15.14 37.74 73.93 D2 T & M 0.02 28.64 55.69 84.70~~

~~D3 0 0.07 16.72 38.01 74.79 D3 m 0.04 30.35 53.11 86.4o D3 T 0.41 17.35 35.88 77.63 D3 T & M 0.48 30.50 56.45 88.31~~

~~Do 0.01 20.12 46.57 78.19 D1 o.35 21.37 43.66 79;69 D2 0.03 21.14 47.25 78.66 D3 0.24 23.75 45.94 81.82~~

~~0 0.17 14.17 39.13 71.43 M 0.01 27.48 51.88 84.98 T 0.26 16.12 38.04 77.42 T & M 0.24 29.01 54.88 84.97 Drought Drought Drought Phase Phase Phase 1 2 3 -175-~~

~~TABLE 44 Field Experiment 1971~~

~~TRANSFORMED DATA % SENESCENCE PER PLANT~~

~~Treatment Blocks Days after sowing 50 64 78 II 9.28 38.94 52.95 0 Do III 21.64 35.12 55.98 IV 21.22 40.45 54.03~~

~~II 19.55 46.26 72.44 0 DI III 28.04 37.64 57.48 IV 23.03 33.90 52.30~~

~~II 6.02 42.76 60.60 0 D2 III 27.69 42.30 58.18 IV 22.63 34.14 54.63~~

~~II 21.81 46.83 78.61 0 D3 III 25.10 34.94 53.55 IV 24.88 32.90 54.39~~

~~Ii 34.20 44.03 67.05 M Do III 31.31 50.94 70.45 IV 31.31 46.03 65.88~~

~~II 24.95 45.17 68.87 PI D1 III 28.18 37.94 65.50 IV 32.71 43.57 62.17~~

~~II 25.84 54.88 66.82 M D2 III 32.01 43.97 71;85 IV 35.91 45.06 64.38~~

~~II 33.46 54.76 75.00 III 28.11 42.07 66,82 IV 38.88 45.11 65.12 -176-~~

~~TABLE 44 (continued)~~

~~Treatment Blocks Days after sowing 50 64 78 II 12.11 40.69 64.75 T Do III 27.35 34.20 68.87 IV 25.70 45.17 57.17~~

~~II 22.71 46.15 71.66 T Dl III 24.12 33.58 56.10 IV 25.55 34.82 64.09~~

~~II 8.91 40.40 60.80 T D2 III 24.95 36.09 58.69 IV 29.13 37.05 58.31~~

~~II 23.89 42.25 71.19 T D3 III 22.79 32.01 59.31+ IV 26.92 36.57 57.42~~

~~II 30.98 44.66 63.51 T & M Do III 29.87 48.04 67.29 IV 33.34 46.55 62.87~~

~~II 34.45 52.77 71.66 T & M D1 III 32.71 48.97 66.42 IV 32.65 42.76 65.42~~

~~II 23.52 43.91 69.33 T & M D2 III 36.51 43.85 70.09 IV 31.76 51.53 62.58~~

~~II 35.18 55.67 72.05 T & M D3 III 34.51 42.99 69.21 IV 30.92 48.22 69.04 -177-~~

~~TABLE '4F (continued)~~

~~ANOVA - REGRESSION LINES FROM TRANSFORMED DATA~~

~~Between disease treatments~~

~~S.V. D.F. S.S. M.S. V.R. p = 0 1 32991.93 32991.93 1197.53 €€ Pi = P2 3 75.3o 25.10 0.91 NS Residual 136 3746.40 27.55~~

~~S.E. between slopes = 1.237~~

~~Between drought treatments~~

~~S.V. D.F. S.S. M.S. V.R. p = o 1 32991.93 32991.93 7019.56 HNN Pi = P2 3 0.359 0.120 0.025 NS Residual 136 639.4o 4.7o~~

~~S.E. between slopes = 0.51 -178-~~

~~TABLE 45 Field Experiment 1971~~

~~MILDEW PER PLANT IN RELATION TO DROUGHT PERIOD AND DISEASE.~~

~~Treatments Days after sowing 36 50 64 78~~

~~Do 0 - o.o6 0.26 1.14 Do M 0.199 1.70 8.02 19.41 Do T - 0.08 0.25 1.12 Dd T & M 0.297 1.05 6.31 8.46~~

~~Dl 0 - 0.16 0.22 1.62 D1 M 0.117 0.63 4.o8 16.49 D1 T - 0.05 1.09 0.26 Dl T & M 0.087 0.49 4.69 6.43~~

~~D2 0 - o.o6 0.63 1.34 D2 M 0.293 1.74 5.31 14.73 D2 T - o.o6 0.62 0.62 D2 T & M 0.248 1.60 6.99 10.69~~

~~D3 0 - 0.07 1.00 1.41 D3 M 0.218 0.76 7.36 19.82 D3 T - 0.05 0.64 0.89 D3 T & M 0.294 1.89 6.46 17.75~~

~~Do 0.117 0.67 3.41 5.89 Dl 0.049 0.31 2.22 5.37 D2 0.142 0.81 2.88 5.04 D3 0.135 o.64 3.40 7.4o~~

~~0 - 0.09 0.54 1.36 M 0.206 1.22 6.22 17.60 T - o.o6 0.64 0.73 T & M 0.224 1.29 6.20 10.62~~

~~Drought Drought Drought Phase Phase Phase 1 2 3 -179-~~

TABLE 46 Field Experiment 1971 ANGULAR TRANSFORM MILDEW LEVEL (%) PER PLANT (78 days after sowing) Treatments Blocks TI TII IV Mean Do 0 - 7.71 7.27 4.99 Do M 21.22 32.27 26.56 26.68 Do T - 9.63 6.29 5.35 Do T & M 20.00 10.94 17.26 16.07

~~D1 0 - 5.47 9.10 4.36 D1 M 23.03 16.35 28.52 22.80 D1 T - 3.09 3.14 2.08 D1 T & M 12.11 8.72 19.19 13.34~~

~~D2 0 , - 8.53 7.49 5.34 D2 M 14.06 33.58 22.46 23.37 D2 T - 4.97 6.02 3.66 D2 T & M 16.11 20.62 19.82 13.85~~

D3 0 - 3.76 9.63 4.46 D3 M 17.26 27.97 27.63 24.29 D3 T - 3.63 7.27 10.90 D3 T & M 9.63 33.71 22.79 22.04 Anova angular transform mildew level 78 days after sowing S.V. D.F. S.S. M.S. V.R. Blocks 2 440.50 220.25 7.00 x Drought 3 58.18 19.39 0.62 NS Plot Error 6 188.80 31.48 Treatments', 3601.1901.19 1200.40 65.52 mix Bl x Tr 32.99 5.50 0.30 NS Dr x Tr 9 110.47 12.27 0.67 NS B1 x Dr x Tr 18 406.71 22.60 1.23 NS Total 47 4938.34 Correction 1 7633.34 Sub Plot Error 24 439.70 18.32 -180-

~~TABLE 47 Field Experiment 1971~~

~~TAKE ALL DISEASE INDEX PER TREATMENT.~~

~~Treatment Blocks II III IV Mean Do 0 12.18 8.82 3.44 8.14 Do M 2.94 18.45 1.63 7.67 Do T 95.94 75.00 61.76 77.56 Do T & M 98.32 89.70 78.36 88.79~~

~~D1 0 11.54 10.89 4.55 8.99 D1 M 2.56 14.28 11.67 9.50 D1 T 95.01 64.75 80.76 80.17 D1 T & M 90.26 81.26 88.16 86.56~~

~~D2 0 4.00 12.90 7.69 8.19 D2 M 13.24 26.37 10.62 16.74 D2 T 89.65 68.15 61.20 73.00 D2 T & M 92.86 82.35 85.18 86.79~~

D3 0 11.43 3.49 4.97 D3 M 3.22 30.30 16.21 16.57 D3 T 55.20 72.86 91.31 73.12 D3 T & M 91.07 87.60 92.86 90.51 ANOVA DISEASE INDEX TAKE-ALL S.V. D.F. S.S. M.S. V.R. Blocks 2 138.788 69.394 0.36 NS Drought 3 4.745 1.582 0.008 NS Plot Error 6 1152.794 192.132

Treatments 3 63192.546 21064.183 239.77 mui B1 x Tr 6 1107.221 184.537 2.10 NS Dr x Tr 9 366.708 40.745 0.46 NS Bl x Dr x Tr 18 1001.252 55.625 0.63 NS Total 47 66964.0539 Correction 1 101935.411 Sub Plot Error 24 2108.473 87.853 S.E. between drought means = 5.659 S.E. between disease means = 3.826 -181-

TABLE 49 Field Experiment 1971 SHOOT HEIGHT (64 days after sowing) (cm) Treatments Blocks II III IV Mean Do 0 75.65 81.20 94.35 90.40 Do M 32.85 80.20 84.90 92.65 Do T 66.70 76.00 73.15 71.95 Do T & M 79.80 73.05 79.70 77.51

~~D1 0 63.60 83.80 83.05 76.81 D1 M 70.20 79.25 79.35 76.26 Dl T 52.70 75.80 71.35 66.61 Dl T & M 60.20 64.70 72.90 65.93~~

~~D2 0 78.60 83.90 83.95 82.15 D2 M 73.60 80.70 87.55 80.61 D2 T 71.75 75.45 68.85 72.01 D2 T & M 69.85 68.85 76.65 71.78~~

D3 0 62.55 87.05 81.90 77.16 D3 M 66.90 87.85 36.05 80.26 D3 T 66.45 79.70 77.25 74.46 D3 T & M 6o.6o 92.30 79.20 74.03 Anova shoot height 64 days after sowing S.V. D.F. S.S. M.S. V.R. Blocks 2 1110.056 555.03 6.62 A Drought 3 309.785 103.26 1.23 NS Plot Error 6 502.930 83.82 Treatments 3 731.813 243.94 4.29 x Bl x Tr 6 147.510 24.59 0.43 NS P1 x Tr 9 125.969 14.00 0.25 NS Bl x P1 x Tr 18 1217.977 67.67 1.19 NS Total 47 3146.040 Correction 1 274813.76 Sub Plot Error 24 1365.437 56.90 S.E. between drought means = 3.74 S.E. between disease means = 3.08 -182-

~~TABLE 49~~

~~MEAN GROWTH (CM) OF COLONIES OF G. GRAMINIS ON AGAR TREATED WITH ETHIRIMOL~~

~~Days after Ethirimol Control inoculation 8% 0.8% 0.08% H2O~~

~~3 - 1.21. 1.03 1.91~~

~~4 - 1.75 1.55 2.92~~

~~5 - 2.48 2.17 4.18~~

~~6 - 3.11 2.70 5.31~~

~~7 - 3.79 3.30 6.61~~

~~9 - 5.00 4.30 7.67~~

~~9 - 6.00 5.10 8.00~~

~~10 - 6.90 5.86 8.00 -183--~~

~~KEY TO TABLES 50 - 61~~

~~Do No drought D Drought~~

~~0 Control M Mildew~~

~~KEY TO TABLES 62 - 67~~

~~N.S. No spray S.B. Spray during stem extension S.C. Spray during grain filling S.B. + C. Spray at both times TABLE 50 Field Experiment 1972~~

~~% MILDEW INFECTION PER PLANT IN RELATION TO TREATMENT~~

~~Treatment Days after sowing 45 55 66 79 91 Do 0 0.01 0.28 0.59 0.89 5.00 Do M 1.23 11.04 27.50 33.95 33.89~~

~~D 0 0.03 0.12 0.35 1.54 D M 1.19 x.53 21.23 39.36 40.61~~

~~Do ' 0.60 5.19 12.21 11.74 13.71 D 0.58 3.59 8.72 12.71 14.76~~

~~0 0.02 0.19 0.47 1.20 4.54 M 1.20 9.77 24.48 36.37 36.51 -185-~~

~~TABLE 51 Field Experiment 1972~~

~~YIELD OF GRAIN (Kg) PER PLOT IN RELATION TO DROUGHT AND MILDEW (Corrected for moisture)~~

~~Treatments Blocks I II III IV Mean~~

~~Do 0 3.127 1.256 1.495 2.057 1.984 Do M 2.729 1.891 1.122 1.344 1.772~~

~~D 0 2.299 2.179 2.058 1.757 2.073 D M 1.354 1.660 1.363 1.333 1.428~~

~~Anova yield~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 3 1.9045 0.6015 1.24 NS Drought 1 0.0649 0.0649 0.13 NS Plot Error 3 1.4540 0.4947~~

~~Treatments 1 0.7362 0.7363 7.45 m El x Tr 3 0.3264 0.1083 1.10 NS Dr x Tr 1 0.1879 0.1979 1.90 NS B1 x Dr x Tr 3 0.2666 0.0889 0.90 NS~~

~~Total 15 4.9404 Correction 1 52.6495 Sub Plot Error 6 0.5930 -186-~~

~~TABLE 52 Field Experiment 1972~~

~~SHOOT NUMBER PER PLOT~~

~~Treatments Blocks I II III IV Mean~~

~~Do 0 3,978 3,720 3,580 4,180 3,864 Do M 2,962 3,260 3,040 3.500 3,191~~

~~D 0 3,280 3,140 3,640 3,080 3,285 D M 3,220 3,390 2,620 2,660 2,970~~

~~Anova shoot number~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 3 62500 20833 0.14 NS Drought 1 640000 640000 4.41 NS Plot Error 3 43460o 144966~~

~~Treatments 1 978121 978121 11.05 w Bl x Tr 3 234323 78107 0.88 NS Dr x Tr 1 128881 129881 1.45 NS Bl x Dr x Tr 3 296603 98867 1.12 NS~~

~~Total 15 2775028 Correction 1 177156100 Sub Plot Error 6 530926 98497 -187-~~

~~TABLE 53 Field Experiment 1972~~

~~SIEVING TEST DATA~~

~~Treatments Mean % grain in each sieve Top Middle Bottom 2.9mm 2.5mm 2.2mm 2.2mm~~

~~Do 0 1.94 26.89 51.60 19.57 Do M 1.58 24.41 50.3 23.18~~

~~D 0 4.66 37.65 46.77 10.92 D M 1.36 22.81 47.44 29.39~~

~~Do 1.76 25.65 51.21 21.37 D 1.50 30.23 47.10 19.65~~

~~0 1.65 32.27 49:418 15.24 1.47 23.61 49.13 25.78 -188-~~

~~TABLE 54 Field Experiment 1972~~

~~ANGULAR TRANSFORM % GRAIN SAMPLE IN TOP SIEVE~~

~~Treatments Blocks I II III IV~~

~~Do 0 9.63 4.87 8.33 8.53 Do M 7.92 9.46 5.23 5.29~~

~~D 0 14.30 11.97 12.92 10.47 D M 7.71 6.02 7.27 5.74~~

~~Anova sieving test~~

~~S.V. D.F. S.S. M.S. V.R. Blocks 3 12.3826 4.1275 5.21 NS Drought 1 18.3612 18.3612 23.17 € Plot Error 3 2.3779 0.7926~~

~~Treatments 1 43.4940 43.4940 12.17 m Bi x Tr 3 9.2118 3.0706 0.86 NS Dr x Tr 1 23.6683 23.6683 6.62 € Bi x Dr x Tr 3 12.2388 4.0796 1.14 NS~~

~~2otal 15 121.7346 Correction 1 1150.2272 Sub Plot Error 6 21.4506 3.5751 -189-~~

~~TABU. 55 Field Experiment 1972~~

~~MEAN INDIVIDUAL LEAF AREA (0142 ) IN RELATION TO DROUGHT AND MILDEW.~~

~~Leaf (1)~~

~~Treatments Blocks I SI III IV Mean~~

~~Do 0 3.35 3.56 3.51 3.66 3.52 Do M 3.57 3.30 3.45 3.39 3.43~~

~~D 0 3.32 3.67 3.72 3.46 3.54 DM 3.53 3.58 3.43 3.52 3.52~~

~~Anova Leaf 1~~

~~S.V. D.F. S.S. M.S. V.R. Blocks 3 0.020 0.007 0.7 NS Drought 1 0.010 0.01 1.00 NS Plot Error 3 0.040 0.01~~

~~Treatments 1 0.020 0.02 0.80 NS B1 x Tr 3 0.100 , 0.033 1.32 NS Dr x Tr 1 0.002 0.002 0.08 NS Bl x Dr x Tr 3 0.050 0.017 0.68 NS~~

~~Total 15 0.24 Correction 1 196.07 Sub Plot Error 6 0.150 0.025 -190-~~

~~TABLE 55 (continued)~~

~~Leaf (2)~~

~~Treatment Blocks I II III IV Mean~~

~~Do 0 4.99 5.20 4.31 5.79 5.05 Do M 5.38 4.90 5.15 5.29 5.18~~

~~D 0 5.17 5.72 5.63 5.79 5.58 D M 5.41 5.00 5.59 5.35 5.34~~

~~Anova Leaf 2~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 3 0.3958 0.1286 0.92 NS Drought 1 0.4761 0.4761 3.40 NS Plot Error 3 0.4196 0.1399~~

~~Treatments 1 0.0121 0.0121 0.82 NS B1 x Tr 3 0.7668 0.2556 1.73 NS Bl x Dr x Tr 3 0.1177 0.0392 0.27 NS~~

~~Total 15 2.3150 Correction 1 446.8996 Sub Plot Error 6 0.8945 0.1474 -191-~~

~~TABU, 55 (continued)~~

~~Leaf (3)~~

~~Treatments Blocks I TI III IV Mean~~

~~Do 0 7.78 8.42 7.31 9.21 8.19 Do M 7.90 7.40 7.76 8.66 7.91~~

~~D 0 7.79 9.20 8.67 8.99 8.66 D M 8.66 9.22 9.22 8.85 8..99~~

~~Anova Leaf 3~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 3 1.9159 0.63% 1.35 NS Drought 1 2.4493 2.4493 5.18 NS Plot Error 3 1.4192 0.4727~~

~~Treatments 1 0.0025 0.0025 0.016 NS Bl x Tr 3 0.8145 0.2715 1.71 NS Dr x Tr 1 0.3600 Q.3600 2.28 NS Bl x Dr x Tr 3 0.1356 0.0452 0.29 NS,T,~~

~~Total 15 7.0960 Correction 1 1139.0502 Sub Plot Error 6 0.9501 0.1594 -192-~~

~~TABLE 55 (continued)~~

~~Leaf (4)~~

~~Treatments Blocks I IT III IV Mean~~

~~Do 0 13.83 14.55 10.92 13.49 13.20 Do M 10.74 12.15 14.50 13.97 12.94~~

~~D 0 13.67 13.04 15.29 17.05 14.76 D M 12.77 12.81 15.84 14.31 13.93~~

~~Anova Leaf 4~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 3 9.6374 ' 3.2125 1.62 NS Drought 1 7.0756 7.0756 3.57 NS Plot Error 3 5.9523 1.9941~~

~~Treatments 1 1.4042 1.4042 2.00 NS Bl x Tr 3 9.9349 3.2783 4.66 NS Dr x Tr 1 0.2256 0.2256 0.32 NS Bl x Dr x Tr 3 7.0541 2.3514 3.34 NS~~

~~Total 15 41.1841 Correction 1 2995.3729 Sub Plot Error 6 16.9890 0.7037 -193-~~

~~TABLE 55 (continued)~~

~~Leaf (5)~~

~~Treatments Blocks I II III IV Mean~~

~~Do 0 16.30 17.00 17.84 20.21 17.84 Do M 12.85 17.80 22.87 23.11 19.18~~

~~DO - 14.66 16.86 17.96 19.55 17.26 DM 23.10 20.21 24.64 23.26 22.90~~

~~Anova Leaf 5~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 3 62.5133 20.8378 5.35 NS Drought 1 9.0860 9.086o 2.33 NS Plot Error 3 11.6933 3.8978~~

~~Treatments 1 46.8200 46.8200 9.83 N Bl x Tr 3 8.9147 2.9716 0.62 NS Dr x Tr 1 19.1599 19.1599 3.81 NS BI x Dr x Tr 3 19.6544 6.5515 1.38 NS~~

~~Total 15 176.9406 Correction 1 5937.7312 Sub Plot Error 6 29.5691 4.7615 -194-~~

~~TABLE 55 (continued)~~

~~Leaf (6)~~

~~Treatments Blocks I II III IV Mean~~

~~Do 0 21.75 22.46 24.63 25.95 23.67 Do M 22.02 22.56 22.14 27.44 23.54~~

~~D 0 25.24 23.98 25.02 25.69 24.98 D M 23.18 22.63 22.38 25.21 23.35~~

~~Anova Leaf 6~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 3 25.8025 9.6008 4.09 NS Drought 1 1.2544 1.25)01 0.60 NS Plot Error 3 6.3105 2.1035~~

~~Treatments 1 3.1152 3.1152 13.18 € Bi x Tr 3 4.9637 1.6546 7.00 N Dr X Tr 1 2.2500 2.2500 9.51 € B1 x Dr x Tr 3 0.7097 0.2366 1.00 NS~~

~~Total 15 44.4060 Correction 1 9179.8470 Sub Plot Error 6 5.634 0.2364 -195-~~

~~TABLE 55 (continued)~~

~~Leaf (7)~~

~~Treatments Blocks I II? III IV Mean~~

~~Do 0 23.99 23.88 22.33 25.34 23.89 Do M 25.01 23.93 24.90 27.94 25.45~~

~~D 0 26.67 25.70 27.18 24.16 25.93 D M 22.04 21.14 25.44 25.50 23.53~~

~~Anova Leaf 7~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 3 9.1630 3.0543 0.85 NS Drought 1 0.0163 0.0163 0.0045 NS Plot Error 3 10.7791 3.5930~~

~~Treatments 1 0.7614 0.7014 0.29 NS Bl x Tr 3 11.6949 3.3993 1.63 NS Dr x Tr 1 15.6618 15.6618 6.54 m B1 X Dr x Tr 3 2.6729 0.8909 0.37 NS~~

~~Total 15 50.6392 Correction 1 9758.9701 Sub Plot Error. 6 14.3676 2.3946 -196-~~

~~TITLE 55 (continued)~~

~~Leaf (8)~~

~~Treatments Blocks I II III IV Mean~~

~~Do 0 15.60 15.44 17.74 16.72 16.39 Do M 16.82 20.44 16.04 17.70 17.75~~

~~D 0 14.10 17.61 16.75 15.82" 16.07 D M 15.57 14.90 19.20 14.51 15.90~~

~~Anova Leaf 8~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 3 7.5033 2.5013 1.81 NS Drought 1 5.1076 5.1076 3.70 NS Plot Error 3 4.1465 1.3822~~

~~Treatments 1 1.2100 1.2100 0.41 NS Bl x Tr .3 1.9529 0.6510 0.22 NS Dr x Tr 1 2.7225 2.7225 0.91 NS Bl x Dr x Tr 3 15.9459 5.3153 1.78 NS~~

~~total 15 38.5991 Correction 1 4354.6801 Sub Plot Error 6 17.9997 2.9831 -197-~~

~~TABLE 55 (continued)~~

~~Leaf (9) (Flag Leaf)~~

~~Treatments Blocks I II III IV Mean~~

~~Do 0 4.21 5.25 4.64 4.71 4.70 Do M 4.89 6.56 4.97 5.29 5.43~~

~~D 0 4.02 5.28 5.29 6.61 5.30 D M 5.02 4.75 6.06 4.24 5.02~~

~~Anova Le of 9~~

~~S .V. D.F. S.S. M.S. V.R.~~

~~Blocks 3 1.9220 0.6407 1.13 NS Drought 1 0.0351 0.0351 0.062 NS Plot Error 3 1.6954 0.5651~~

~~Treatments 1 0.1957 0.1957 0.31 NS Bl x Tr 3 1.7655 0.5985 0.92 Na Dr x Tr 1 1.0151 1.0151 1.58 NS B1 x Dr x Tr 3 2.0910 0.6937 1.08 Na~~

~~Total 15 8.7098 Correction 1 418.1003 SubPlot Error 6 3.9465 0.6411 TABLE 56 Field Experiment 1972~~

~~MEAN LEAF AREA (CM2.) PRODUCED PER PLANT IN RELATION TO TREATMENTS~~

~~Treatment Days after sowing 45 55 66 79 91~~

~~Do 0 46.72 91.02 119.10 116.02 116.02 Do M 44.94 92.90 123.17 120.42 120.42~~

~~D 0 55.20 103.66 126.07 121.87 121.87 D M 54.54 91.49 125.38 122.27 122.27~~

~~Do 45.83 91.96 120.63 113.22 118.22 D 54.87 97.57 125.73 122.07 122.07~~

~~0 50.96 92.34 122.09 113.95 119.95 49.74 97.19 124.28 121.34 121.34 -199-~~

~~TABLE 57 Field Experiment 1972~~

~~TOTAL LEAF AREA PRODUCED PER PLANT (79 days after sowing) IN RELATION TO DROUGHT AND DISEASE.~~

~~Treatments Blocks I TT IIT IV Mean~~

~~Do 0 111.98 115.21 113.19 123.70 116.02 Do M 108.03 119.10 121.79 132.77 120.42~~

~~D 0 114.66 119.80 125.66 127.37 121.87 D M 119.28 114.24 130.90 124.75 122.27~~

~~Anova Total leaf area produced 79 days after sowing~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 3 440.253 146.751 4.02 NS Drought 1 59.29 59.28 1.63 NS Plot Error 3 109.435 36.48~~

~~Treatments 1 22.98 22.98 1.42 NS Bl x Tr 3 35.36 11.79 0.73 NS Dr x Tr 1 16.06 16.06 0.99 NS Bl x Dr x Tr 3 61.765 20.59 1.27 NS~~

~~Total 15 745.133 Correction 1 230957.136 Sub plot Error 6 97.125 16.19~~

~~TABLE 58 Field Experiment 1972~~

~~MEAN GREEN LEAF AREA (CM2) PER PLANT IN RELATION TO TREATMENTS~~

~~Treatments Days after sowing 45 55 66 79 91~~

~~Do 0 46.55 72.75 75.67 44.73 19.55 Do M 44.42 61.21 57.45 21.87 8.44~~

~~D 0 54.59 88.72 80.02 42.96 12.77 D M 50.10 62.12 53.46 18.06 5.40~~

~~Do 45.49 66.98 66.56 33.30 14.00 D 52.34 75.41 66.74 30.51 9.09~~

~~0 50.57 80.73 . 77.84 • 43.85 16.16 M 47.26 61.66 55.46 19.96 6.92 -201-~~

~~TABLE 59 Field Experiment 1972~~

~~GREEN LEAF ARE PER PLANT (79 days after sowing) IN RELATION TO DROUGHT AND DISEASE.~~

~~Treatments Blocks II III IV Mean~~

~~Do 0 38.92 1+4.15 49.64 46.21 44.73 Do M 29.28 20.02 18.08 20.09 21.87~~

~~D 0 40.49 44.14 46.58 40.63 42.96 D M 16.65 20.68 15.04 19.85 18.06~~

~~Anova Green leaf area 79 days after sowing~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 3 2.6889 0.9963 0.15 NS Drought 1 31.136 31.136 5.40 NS Plot Error 3 17.2921 5.764~~

~~Treatments 1 2281.973 2291.973 93.74 30i* Bl x Tr 3 109.9963 36.6655 1.35 NS Dr x Tr 1 4.1619 4.1619 0.15 NS Blx Dr x Tr 3 53.5159 17.8386 0.65 NS~~

~~Total 15 2500.7641 Correction 1 16284.3121 Sub Plot Error 6 163.5122 27.252 TABTg 60 Field Experiment 1972~~

~~MEAN % SENESCENCE PER PLANT IN RELATION TO TREATMENT~~

~~Treatment Days after sowing 45 55 66 79 91~~

~~Do 0 0.35 10.21 35.93 61.45 83.15 Do M .1.16 26.15 53.35 81.94 92.99~~

~~D 0 1.11 14.41 36.53 64.75 89.52 D M 8.15 32.11 57.36 85.23 95.58~~

~~Do 0.75 18.27 44.82 71.83 99.16 D 4.61 22.71 46.92 75.01 92.56~~

~~0 0.77 12.57 36.24 63.14 86.41 M 4.92 29.28, 55.38 83.55 94.30 -203-~~

~~TABLE 61 Field Experiment 1972~~

~~ANGULAR TRANSFORM OF % SENESCENCE PER PLANT IN RELATION TO TREATMENT.~~

~~Treatment Block Days after sowing 56 66 79 91~~

~~I 19.46 62.71 53.95 66.11 15.23 37.82 51.77 654 50 0 Do III 13.69 34.99 49.50 61.48 IV 23.34 37.53 52.30 70.18~~

~~I 20.79 36.03 53.55 67.21 II 24.27 37.17 52.65 72.34 0 D III 23.34 36.93 52.49 71.09 IV 20.44 38.59 55.61 74.00~~

~~I 29.20 43.62 58.63 69.56 II 25.92 45.80 65.90 74.44 M Do III 31.37 48.33 67.37 76.82 IV 35.12 49.31 67.13 79.03~~

~~I 33.02 47.64 68.03 78.17 35,55 47.59 64.82 77.21 M D III 35.79 51.94 70.18 76.95 IV 33.52 49.43 66.50 79.22~~

~~-201+ -~~

~~TABLE 61 (continued)~~

~~Anova regression lines from transformed data~~

~~Between disease treatments~~

~~S .V. D.F. S.S. M.S. V.R.~~

~~p = o 1 18929.24 19929.24 1152.32 3i3Em~~

~~)32 1 15.60 15.60 0.95 NS~~

~~Residual 62 1017.82 16.42~~

~~S.E. between slopes = 1.013~~

~~Between drought treatments~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~= 0 1 19929.24 19929.24 4272.97 mei~~

~~131 = P2 1 3.100 3.100 0.70 NS~~

~~liesidual 62 274.94 4.43~~

~~S.E. between slopes = 0.5263 TABLE 62 Field Experiment 1972~~

~~MEAN % MILDEW PER PLANT IN RELATION TO SPRAY APPLICATION~~

~~Treatment Days after sowing 48 57 68 82 96 r.)~~

~~No spray 1.01 3.26 11.04 19.87 34.64~~

~~Spray B 0.75 2.51 3.43 1.99 10.21~~

~~Spray C 0.82 2.88 7.25 12.84 9.58~~

~~Spray B f C 0.72 2.38 2.56 2.11 2.22 -206-~~

~~TABLE 63 Field Experiment 1972~~

~~YIELD PER PLOT (Kg) IN RELATION TO SPRAY APPLICATION (corrected for moisture).~~

~~Treatment Blocks I II III IV~~

~~No spray 3.144 3.232 2.766 4.289 2.656 2.453 3.617 3.140~~

~~Spray B 4.175 4.043 4.580 4.730 3.208 3.914 3.847 3.453~~

~~Spray C 2.619 3.203 3.554 4.329 2.984 3.512 4.092 3.402~~

~~Spray B + C 3.109 4.341 4.932 4.935 2.706 3.031 4.413 4.145~~

~~Anova Yield~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~Blocks 3 4.93 1.66 6.19 €€~~

~~Treatments 3 3.76 1.25 0.47 NS~~

~~Error 25 6.702 0.268~~

~~Total 31 15.442 Correction 1 424.227 TABLE 64 Field Experiment 1972~~

~~MEAN LEAF AREA '(CM2) PRODUCED PER PLANT IN RELATION TO SPRAY APPLICATION~~

~~Treatment Days after sowing 48 57 68 82 96~~

~~No spray 50.34 82.82 127.76 131.23 131.23~~

~~Spray B 50.52 82.49 124.34 129.04 129.04~~

~~Spray C 47.95 80.96 127.86 130.31 130.31~~

~~Spray B + C 49.14 83.00 130.45 131.83 131.83 TABLE 65 Field Experiment 1972~~

~~MEAN GREEN LEAF AREA (CM2 ) PER PLANT IN RELATION TO SPRAY APPLICATION.~~

~~Treatment Days after sowing 48 57 68 82 96~~

~~No spray 49.91 68.63 74.00 47.17 25.80~~

~~Spray B 49.96 72.54 80.69 67.22 32.51~~

~~Spray C 47.70 72.30 78.56 52.11 39.67~~

~~Spray B + C 48.98 73.08 93.56 73.65 44.62 TABLE 66 Field Experiment 1972~~

~~MEAN % SENESCENCE PER PLANT IN RELATION TO SPRAY APPLICATION.~~

~~Treatment Days after sowing 48 57 68 82 96~~

~~No spray 0.85 17.14 42.08 64.05 80.34~~

~~Spray B 1.10 12.05 35.11 47.91 74.81~~

~~Spray C 0.51 10.72 38.55 60.01 69.56~~

~~Spray B + C 0.53 11.95 28.28 44.14 66.15 -210-~~

~~TABLE 67 Field Experiment 1972~~

~~ANGULAR TRANSFORM OF PERCENTAGE SENESCENCE PER PLANT.~~

~~Treatment Days after sowing 57 68 82 96~~

~~N.S. 24.27 40.34 56.29 61.75 30.72 49.31 56.29 68.28 20.70 39.23 50.77 63.58 21.81 37.64 53.25 58.12 37.64 54,09 69.03 42.65 54.94 62.03 33.46 47.41 60.97 44.49 53.13 69.82~~

~~S. B. 13.05 35.30 44.25 55.73 16.22 36.27 45.75 63.87 22.14 39.47 42.42 58.37 26.49 34.57 43.17 63.29 35.73 43.17 59.74 39.23 46.15 64.90 32.77 39.93 55.98 37.41 46.03 59.50~~

~~S.C. 12.52 33.34 52.24 52.36 22.14 41.03 51.41 59.18 20.96 34.57 50.93 57.92 19.19 33.53 47.45 59.24 38.88 54.03 56.54 36.21 45,69 53.37 41.27 53.91 57.67 43.28 50.30 57.90~~

~~-211-~~

~~TABLE 67 (continued)~~

~~Treatment Days after sowing 57 68 82 96~~

~~S. B C 16.64 34.88 42.99 55.30 19.24 29.73 42.99 55.18 20.18 33.27 42.99 57.48 25.94 41.27 46.72 61.14 29.60 39.35 51.53 27.29 36.99 53.97 32.14 40.63 49.79 29.06 40.99 51.94~~

~~Anova - Regression lines fron above data~~

~~S.V. D.F. S.S. M.S. V.R.~~

~~ft = 0 1 17244.69 17244.69 893.04 *3Ex~~

~~P1 = P2 3 4995 16.65 0.86 NS~~

~~Residual 104 2008.17 19.31~~

~~Overall slope = 0.90 -212-~~

~~TABLE 68~~

~~MEAN CHLOROPHYLL LEVEL (mg/cm2) PER LEAF.~~

~~Control Mildew infected D.a.s. Leaf No. Chl a Chl b Chl a Chl b~~

~~15 1 0.027 0.009 0.026 0.008 2 0.022 0.007 0.019 0.006~~

~~20 1 0.022 0.007 0.021 0.007 2 0.026 0.008 0.023 0.007 3 0.017 0.005 0.017 0.005~~

~~25 1 0.025 0.008 0.012 0.005 2 0.022 0.007 0.010 0.004 3 0.019 o.006 0.022 0.005 4 0.016 0.005 0.016 0.005~~

~~3o 1 0.023 0.007 0.006 0.002 2 0.024 0.008 0.007 0.002 3 0.021 o.006 0.011 0.003 4 0.021 0.007 0.017 0.005 5 0.017 0.005 0.016 0.005 -213-~~

~~TABLE 69~~

~~MEAN LEAF AREA (CM2) PRODUCED PER PLANT IN RELATION TO TREATMENT~~

~~CONTROL ETHIRIMOL DRESSED Days after Control Mildew Control Mildew sowing infected infected~~

~~17 10.57 15.33 7.86 14.82~~

~~20 20.94 17.42 19.21 18.30~~

~~23 28.35 21.09 20.68 30.28~~

~~26 35.91 34.42 33.29 42.34~~

~~29 42.79 50.62 48.19 59.90~~

~~32 61.73 51.88 55.79 58.39~~

~~35 72.39 73.39 70.46 91.79~~

~~38 90.59 85.89 92.51 87.35~~

~~41 97.05 99.13 114.56 111.20~~

~~44 103.72 105.75 121.36 127.17 -214-~~

~~TABLE 70~~

~~LEAF AREA (CM2) PRODUCED PER PLANT 44 days after sowing~~

~~Treatment Replicate 1 2 3 4 5 Control Control 126.78 87.29 110.28 101.28 109.67 Mildew 119.08 113.36 117.77 77.20 122.68 Infected~~

~~Ethirimol Dressed Control 135.20 123.19 145.92 124.86 91.78 Mildew 129.91 117.63 130.74 133.42 126.78 Infected~~

~~Anova leaf area produced~~

~~Source D.F. S.S. M.S. V.R.~~

~~Replicates 4 1267.3544 316.84 1.68 NS Mildew 1 49.42 49.42 0.26 NS Plot Error 4 755.46 189.87~~

~~Chemical 1 1499.21 1499.21 6.03 x Reps x Ch 4 1220.66 305.17 1.23 NS Mil x Ch 1 0.14 0.14 0.00 NS Reps x Mil x Ch 4 767.56 191.39 0.77 NS~~

~~Total 19 5559,80 Correction 1 274646.4845 Sub plot Error 8 1938.22 248.53~~

~~-215-~~

~~TABLE 71~~

~~MEAN GREEN LEAF AREA (CM2) PER PLANT IN RELATION TO TREATMENT.~~

~~CONTROL ETHIRIMOL DRESSED Days after Control Mildew Control Mildew sowing infected infected~~

~~17 10.57 15.33 7.86 14.82~~

~~20 20.94 16.82 19.21 18.30~~

~~23 28.35 19.0o 20.68 30.28~~

~~26 35.91 30.59 33.29 42.94~~

~~32 61.57 27.79 54.10 57.59~~

~~35 71.44 49.49 65.87 90.96~~

~~38 78.79 45.73 82.79 76.01~~

~~41 94.23 46.25 99.65 90.62~~

~~44 94.2o 44.4o 102.76 103.96 -216-~~

~~TABLE 72~~

~~GREEN LEAF AREA (CM2) PER PLANT 44 days after sowing~~

~~Treatment Replicate 1 2 3 4 5 Control Control 111.35 66.96 95.16 95.07 86.59 Mildew Infected 51.03 50.63 48.23 28.05 65.32~~

~~Ethirimol Dressed Control 112.29 96.07 135.22 113.28 76.22 Mildew Infected 103.74 100.49 110.69 107.09 112.17~~

~~Anova green leaf area~~

~~Source D.F. S.S. . M.S. V.R.~~

~~Replicate 4 1073.42 268.36 0.67 NS Mildew 1 2116.04 2116.04 5.25 NS Plot Error 4 1611.21 402.90~~

~~Chemical 1 7365.89 7365.89 50.29 mix Reps x Ch 4 996.49 221.62 1.51 NS Mil x Ch 1 1958.62 1958.62 13.37 Hai Mil x Ch x Reps 4 285.22 71.31 0.49 NS~~

~~Total 19 15296.89 Correction 1 155003.22 Sub Plot Error 8 1171.71 146.46 -217-~~

~~TABLE 73~~

~~MEAN SHOOT DRY WEIGHT (g) IN RELATION TO INFECTION AND CHEMICAL TREATMENT~~

~~CONTROL ETHIRIMOL DRESSED Days after Control Mildew Control Mildew sowing infected infected~~

~~17 0.0149 0.0200 0.0150 0.0215~~

~~20 0.0324 0.0309 0.0289 0.0313~~

~~23 0.0453 0.0370 0.0364 0.0449~~

~~26 0.0603 0.0626 0.0629 0.0759~~

~~29 0.0903 0.1016 0.0868 0,1104~~

~~32 0.1093 0.1060 0.1141 0.1353~~

~~35 0.1460 0.1487 0.1522 0.2176~~

~~38 0.2066 0.1920 0.1941 0.2364~~

~~0.2137 0.2059 0.2647 0.3358~~

~~44 0.2827 0.2411 0.3119 0.4600 -218-~~

~~TABLE 74~~

~~SHOOT DRY WEIGHT (g) 44 days after sowing~~

~~Treatment Replicate 1 2 3 4 5 Control Control 0.4370 0.2077 0.2720 0.2010 0.2958 Mildew Infected 0.3490 0.2000 0.2090 0.1606 0.2870~~

~~Ethirimol Dressed Control 0.4193 0.2458 0.4060 0.3100 0.1782 Mildew Infected 0.4610 0.3850 0.4694 0.4495 0.5350~~

~~Anova shoot dry weight~~

~~Source D.F. S.S. M.S. V.R.~~

~~Replicate 4 0.0594 0.0149 2.53 NS Mildew 1 0.0142 0.0142 2.41 NS Plot Error 4 0.0234 0.0059~~

~~Chemical 1 0.0769 0.0769 20.24 €€ Reps x Ch 4 0.0206 0.0052 1.37 NS Mil x Ch 1 0.0451 0.0451 11.87 m* Mil x Ch x Reps 4 0.0099 0.0025 o.66 NS~~

~~Total 19 0.2495 Correction 1 2.0986 Sub Plot Error 8 0.0305 0.0038 -219-~~

~~TABLE 75~~

~~MEAN ROOT DRY WEIGHT (g) IN RELATION TO INFECTION AND CHEMICAL TREATMENT~~

~~CONTROL ETHIRIMOL DRESSED Days after Control Mildew Control Mildew sowing infected infected~~

~~17 0.0174 0.0222 0.0226 0.0259~~

~~20 0.0271 0.0243 o.0251 0.0270~~

~~23 0.0284 .0.0259 0.0269 0.0295~~

~~26 0.0346 0.0319 0.0347 0.0388~~

~~29 0.0491 0.0444 0.0489 0.0631~~

~~32 0.0674 0.0450 0.0780 0.0754~~

~~35 0.0919 0.0627 0.0966 0.1340~~

~~38 0.1561 0.0791 0.1147 0.2286~~

~~41 0.1414 0.0930 0.3046 0.2496~~

~~44 0.2199 0.1121 0.2.391 0.3333 -220-~~

~~TABLE 76~~

~~ROOT DRY WEIGHT (g) 44 days after sowing~~

~~Treatment Replicate 1 2 3 4 5 Control Control 0.2756 0.2120 0.1470 0.2144 0.2455 Mildew 0.0977 0.0757 Infected 0.1910 0.1074 0.0987~~

~~Ethirimol Dressed Control 0.3128 0.2123 0.2793 0.2817 0.1053 Mildew 0.3083 0.3236 Infected 0.4243 0.2607 0.3498~~

~~Anova root dry weight~~

~~Source D.F. S.S. M.S. V.R.~~

~~Replicate 4 0.0221 0.0055 2.50 NS Mildew 1 0.0002 0.0002 0.091 NS Plot Error 4 0.0097 0.0022~~

~~Chemical 1 0.0724 0.0724 21.94 xm Reps x Ch 4 0.0090 0.0023 0.697 NS Mil x Ch 1 0.0509 0.0509 15.42 RA Mil x Ch x Reps 4 0.0173 0.0043 1.303 NS~~

~~Total 19 0.1906 Correction 1 1.0194 Sub plot Error 9 0.0263 0.0033 -221-~~

~~TABLE 77~~

~~MEAN TOTAL CHLOROPHYLL LEVEL PER PLANT (mg/g) IN RELATION TO INFECTION AND CHEMICAL TREATMENT~~

~~CONTROL ETHIRIMOL DRESSED Days after Control Mildew Control Mildew sowing infected infected~~

~~17 27.194 25.000 26.630 27.561~~

~~20 24.670 21.754 25.007 24.327~~

~~23 23.405 22.182 23.115 23.488~~

~~26 25.392 21.347 24.426 22.620~~

~~29 21.728 17.591 21.967 21.119~~

~~32 20.948 14.663 18.927 19.738~~

~~17.800 13.598 15.425 15.226~~

~~38 14.757 11.128 15.243 14.979~~

~~41 15.549 9.924 13.861 12.916~~

~~44 13.297 9.090 12.181 11.042 -222-~~

~~TABLE 78~~

~~TOTAL CHLOROPHYLL LEVEL PER PLANT (mg/g) IN RELATION TO INFECTION AND CHEMICAL TREATMENT.~~

~~Control~~

~~Days after Replicates sowing 1 2 3 4 5~~

17 27.128 26.369 30.150 21.559 25.130 20 23.979 24.000 25.239 24.219 26.012 23 25.508 21.064 26.046 21.598 22.807 26 24.646 24.707 25.297 27.800 24.512 29 21.031 21.499 22.017 22.748 21.345 32 19.593 20.391 22.353 21.306 21.118 35 18.051 19.207 17.841 17.085 16.816 38 16.145 13.519 14.410 15.163 14.550 41 15.24o 16.959 16.o24 14.179 15.342 44 12.372 14.579 13.087 14.144 12.253

~~Mildew Infected~~

17 23.620 25.654 26.796 24.129 24.905 20 23.872 20.687 21.058 21.312 21.841 23 20.910 22.731 21.690 24.976 20.713 26 20.095 19.634 24.059 22.306 20.642 29 18.296 16.476 21.879 15.115 16.188 32 13.323 15.473 16.542 13.601 14.376 35 12.467 12.733 14.432 13.415 14.943 38 11.965 11.703 10.749 10.943 10.393 41 10.760 10.754 9.490 9.744 8.884 44 9.494 8.757 8.603 9.924 8.683 -223-

~~TABLE 78 (continued)~~

~~Days after Replicates sowing 1 2 3 4 5~~

Ethirimol dressed - no mildew 17 22.323 25.630 30.893 25.953 28.361 20 24.663 24.495 24.337 24.693 26.850 23 21.063 23.548 24.939 23.101 22.926 26 22.521 23.724 23.957 27.718 24.308 29 22.404 22.226 21.333 22.383 21.488 32 16.308 17.649 20.204 19.357 21.117 35 13.854 16.875 17.192 15.723 13.493 38 15.248 15.914 15.978 15.744 13.529 41 15.281 15.575 14.229 11.993 12.325 44 9.007 12.417 11.246 12.974 15.259

Ethirimol dressed - mildew infected 17 26.685 24.452 33.882 25.496 27.290 20 23.988 23.827 25.723 23.701 24.396 23 22.004 24.04o 23.409 24.047 23.941 26 21.629 23.131 23.777 22.930 21.635 29 21.562 20.573 19.972 21.404 22.086 32 18.921 20.457 19.867 21.036 18.408 35 13.699 14.498 14.968 15.198 17.779 38 14.167 15.758 16.092 13.712 14.669 41 11.210 12.001 15.565 13.402 12.402 44 10.530 10.816 9.321 11.635 12.908

Anova - Regression lines - chlorophyll level/time S.V. •D.F. S.S. M.S. V.R. 1 4799.345 4799.345 1465.002 RR.*

~~= P2 3 32.745 10.915 3.332 NS~~

~~Residual 192 628.971 3.276 FIG 41~~

~~°AD MILDEW PER PLANT IN RELATION TO CHEMICAL TREATMENT~~

~~KEY~~

~~NO • - MILDEW~~

~~ETHIRIMOL %~~

~~- MILDEW MILDEW ETHIR1MOL~~

~~DRESSED~~

~~DAYS AFTER SOWING -225-~~

~~TABLE 79~~

~~% MILDEW PER PLANT IN RELATION TO TREATMENT~~

~~CONTROL ETHIRIMOL DRESSED Days after Control Mildew Control Mildew sowing infected infected~~

~~17 - 5.28 - =11.~~

~~20 - 10.46 WEN 01111•~~

23 - 13.26 AO*

~~26 - 23.90 - -~~

~~29 - 38.79~~

~~32 - 30.48 - 2.48~~

~~35 - 21.92 - 4.50~~

~~38 - 40.98 - 1.82~~

~~41 - 37.17 - 4.87~~

~~44 - 9.14 - 4.50 -226-~~

~~APPENDIX III~~

~~Experiment (3)~~

This experiment was designed to yield further information on the effect of ethirimol on plant growth and also investigate more thoroughly the interaction between take-all and mildew noted in the field in 1971. It was decided that in this experiment sampling of chlorophyll should be delayed to later in the growth when measurements during stem extension could be made.

~~There were eight treatments, the experiment being sown on 15 February 1973 in Sin (7.5cm) pots as before.~~

~~Ethirimol No take-all~~

~~Ethirimol Take -all~~

~~Spore-free cabinet No ethirimol No take-all No ethirimol Take -all~~

~~Ethirimol No take-all Ethirimol Take-all 'Mildew' cabinet No ethirimol No take-all No ethirimol Take-all~~

A sufficient number of replicates was sown to allow for the destructive sampling of chlorophyll during growth. Seeds were treated with 0.8% w/w a.i. ethirimol as before, and take-all was introduced to -227-

~~pots by placing three grains infected with G. graminis (Materials and Methods p 17 ) in each pot before sowing the normal grain.~~

~~Mildew was introduced on 27 February (12 days after sowing) spread of infection being by natural means after this time.~~

Measurements of leaf area, mildew infection and senescence were made on five marked plants per treatment every three days from 2 March (15 days after sowing) to 39 days after sowing. At this time 5 other plants per treatment were also measured in the same way, but the shoots were then cut off at soil level, dried and the roots carefully washed out, examined for take-all and also dried for 49 h at 70°C.

No take-all whatsoever was found at this sample and therefore as one of the primary objectives had not been fulfilled the experiment was terminated. The five marked plants per treatment were measured, cut and dried as the others previously. For this reason, results for supposedly take-all infected plants have been omitted.

The results show a slightly different picture to that in the last experiment, although there is no change in the leaf area produced (Fig -+2 ) there is a sudden drastic reduction in the green leaf area of plants treated with ethirimol but subjected to mildew (Fig +3 ). -228-

This can only be attributed to a breakdown in the resistance to mildew granted by the chemical because of the massive attack of mildew present in the cabinet, which provided optimal condition for mildew development.

~~Here again, however, ethirimol has led to some increase in growth (Fig 42) and caused a significant reduction in the rate of senescence of plants not subjected to mildew attach.~~

~~Fig 411- shows the level of mildew attach prevalent, the figures being comparatively low because of the degree of senescence initiated.~~

~~Table 90 shows the mean dry weights of the roots and shoots of the marked plants.~~

~~Table 80 - Mean dry weight shoots and roots in relation to infection and chemical treatment.~~

~~Treatment Shoot L.S.D. Root L.S.D. p=0.05 p=0.05 No Milstem No Mildew 0.62 0.67 Milstem No Mildew 0.69 0.44 0.05 0.13 No Milstem Mildew 0.37 o.14 Milstem Mildew 0.72 0.53~~

~~This demonstrates again that ethirimol has led to an increase in growth even in the presence -229-~~

of mildew. Roots again show the most marked differences in weight, t)ough here the control plants have the largest root systems, but ethirimol does give some advantage where mildew is present. FIG 42 MEAN LEAF AREA PRODUCED PER PLANT IN RELATION TO 1 NFECTION AND CHEMICAL TREATMENT j20 L.S. D.

~~100~~

~~80 KEY AREA NO o - CONTROL CM 2 60 ETHIRIMOL ® - MILDEW~~

~~40 E THIRIMOL 0 - CONTROL~~

~~DRESSED ® - MILDEW 20~~

~~20 30 40~~

~~DAYS AFTER SOWING •FIG 43~~

~~MEAN GREEN LEAF AREA PER PLANT IN RELATION TO INFECTION~~

~~AND CHEMICAL TREATMENT~~

~~cH/>ci~~

~~80 0 ■ • KEY AREA I L.S. D. 2 ■ CM NO o - CONTROL~~

~~ETHIRIMOL • - MILDEW~~

~~ETHIRIMOL ❑ - CONTROL~~

~~DRESSED • — MILDEW~~

~~DAYS AFTER SOWING FIG 44~~

~~°/o MILDEW IN RELATION TO CHEMICAL TREATMENT~~

~~0/0~~

~~MILDEW s - NO ETHIRIMOL~~

~~25 o — ETHIRIMOL DRESSED~~

~~20 30 40~~

~~DAYS AFTER SOWING~~