Development of Burley 21, the First Wildfire-Resistant Tobacco Variety, Including Results of Variety Trials

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12-1960

Development of Burley 21, the First Wildfire-Resistant Tobacco Variety, including Results of Variety Trials

University of Tennessee Agricultural Experiment Station

Howard E. Heggestad

E. E. Clayton

M. O. Neas

H. A. Skoog

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Recommended Citation University of Tennessee Agricultural Experiment Station; Heggestad, Howard E.; Clayton, E. E.; Neas, M. O.; and Skoog, H. A., "Development of Burley 21, the First Wildfire-Resistant Tobacco Variety, including Results of Variety Trials" (1960). Bulletins. https://trace.tennessee.edu/utk_agbulletin/265

The publications in this collection represent the historical publishing record of the UT Agricultural Experiment Station and do not necessarily reflect current scientific knowledge or ecommendations.r Current information about UT Ag Research can be found at the UT Ag Research website. This Bulletin is brought to you for free and open access by the AgResearch at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Bulletins by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. '--::~-J development of BURLEY 21, the first wildfire-resistant• tobacco variety,

including results « i' of variety trials DEc G-1931 ~ Bulletin 321 Howard E. Heggestad E. E. Clayton December• M. O. Neas 1960 H. A. Skoog

Crops Research Division, Agricultural Research Service United States Department of Agriculture in cooperation with The University of Tennessee Agricultural Experiment Station John A. Ewing, Director . Knoxville SUMMARY

• Burley 21 released for planting in 1955 has high resistance to wildfire transferred from the species N. longiflora and resistance to tobacco mosaic of the local-lesion type originally obtained from N. glutinosa. It is the first wildfire-resistant tobacco variety of any type to be developed. The transfer of wildfire resistance and development of Burley 21 involved six backcrosses after successful production of the inter-specific hybrid. The last five of these were with burley varieties and breeding lines. When Burley 21 was released, there had been eight generations of selfing, with critical testing in each generation to stabilize resistance to wildfire and to select breeding lines with widest adaptability. Burley 21 combines disease resistance with good standup type, high quality, and high- yielding ability. It has been outstanding in production performance as measured by values for crop index and dollar returns per acre in variety tests conducted for the past 8 years in many locations in the burley-producing region . • Three experimental lines from the same cross as Burley 21, namely, Gr. 25A, Gr. 25B, and Gr. 25C and also other closely related lines, Gr. 26, Gr. 27, Gr. 28, Gr. 29, and Gr. 30, were included in advance variety trials; however, they were rejected for various reasons. Gr. 25A was unusually susceptible to a root disease believed caused by a strain of Phytophthora parasitica. Gr. 26 and Gr. 30 were inferior in quality as judged by manufacturing companies, although they were very high yielding and otherwise met burley variety requirements . • Gr. 25 released as Burley 21 was generally acceptable to the tobacco companies which took part in the quality evaluations of varieties and breeding lines. Tests for disease resistance in plant beds and fields and the breeding procedures are described. The most intensive selection work leading to the development of Burley 21 was performed from 1951 through 1954. Most tests were conducted at the Tobacco Experiment Station; however, Gr. 25 was included in many variety trials in Tennessee and elsewhere throughout the burley tobacco-producing region . • Yield and quality tests conducted in the presence of wildfire and tobacco mosaic showed that susceptible varieties Burley 1 and Kentucky 16 averaged only 54 percent of the yield of resistant Burley 21 when plants were inoculated with wildfire bacteria and tobacco mosaic virus, and 84 percent of Burley 21 yields

2 when inoculated only with wildfire bacteria. In another experiment, the susceptible varieties produced average yields which were 62 percent of Burley 21 yields when plants were inoculated with the pathogens causing both diseases and 81 percent when inoculated only with wildfire bacteria. Grade-index values of the susceptible varieties averaged 30 percent lower than Burley 21 values if inoculated with wildfire bacteria and 38 percent lower if inoculated with wildfire bacteria and tobacco mosaic virus . • Especially in the dry season of 1952 a stalk and root disease resulted in 45 and 21 percent reduction in stand of Gr. 25A at two variety test locations. Significantly less disease injury of this type was found in Gr. 25 and the other wildfire-resistant lines. Because of its susceptibility, Gr. 25A was discontinued. Attempts to reproduce the disease by inoculation were negative and only in 1953 at two locations were a few plants with similar symptoms found . • Analysis of tobacco grades over a 3-year period involving 28 replicated variety tests revealed that Burley 21 produced 2 percent more flyings and 3 percent more in cutter grades than Ken- tucky 16. It produced 6 percent less in leaf grades. Burley 21 produced about 10 percent more tobacco in the light-colored buff grades than Kentucky 16. • Burley 21, Burley 1, Burley 2, and Kentucky 16 produced almost the same nicotine level according to analyses of flyings, cutters, and leaf grades from three variety test locations during a 3-year period, 1951-1953. Continued plant selection in 1957, 1958, and 1959 within the foundation seed planting of Burley 21 resulted in additional quality improvement; that is, a reduction of nornicotine content was affected-especially in 1957-by using the paper chromatography technique to identify the plants which had a low level of this alkaloid, and then saving seed only from these plants.

COVER PHOTO (also Figure 8): Susceptible plants died because disease developed after the plants were inoculated weekly with wildfire bacteria. 3 ACKNOWLEDGMENTS

Grateful acknowledgment is made to J. Hugh Felts, Super- intendent of the Tobacco Experiment Station, Greeneville, Tennessee, who helped conduct the experimental work; to D. R. Bowman and R. N. Jeffrey, Plant Physiologists, Crops Research Division, Agricultural Research Service, U. S. De- partment of Agriculture, Knoxville, Tennessee, and Beltsville, Maryland, respectively, for chemical analysis; to the American Tobacco Company, the R. J. Reynolds Tobacco Company, and the Liggett & Myers Tobacco Company for quality determinations; to the Tobacco Division, Agricultural Marketing Serv- ice, USDA, for grading the experimental lots of tobacco; to Branch Tennessee Experiment Station superintendents and growers whose cooperation made the variety tests possible; and, to the personnel of the Extension Service who helped evaluate Burley 21.

4 CONTENTS

Page SUMMARY 2

INTRODUCTION 6

WILDFIRE, A BACTERIAL LEAF SPOT DISEASE _ 8

DESCRIPTION OF BURLEY 21 AND HISTORY OF ITS DEVELOPMENT______11 Pedigree of Burley 2111 Procedure for Testing for Wildfire Resistance and Yield and Quality _17 Agronomic Results with Breeding Lines and Varieties, 1950 ______19 Agronomic Results with Breeding Lines and Varieties, 1951 21 Results of Yield and Quality Tests conducted with Susceptible and Resistant Tobaccos in Presence of Wildfire and Tobacco Mosaic______25 Resistance to Blackfire, (Angular Leafspot) 28 Agronomic Results with Breeding Lines and Varieties, 1952 . 32 A "New" Disease Attacks some Wildfire-Resistant Breeding Lines...... ___ 35 Agronomic Results with Breeding Lines and Varieties, 1953______36 Agronomic Results with Breeding Lines and Varieties, 195441 Performance of Burley 21 in Regional Variety Tests 43 Cured Leaf Characteristics of Burley 21 44 Nicotine Content of Burley 21 and other Varieties 47

DISCUSSION ___49 LITERATURE CITED _. ____ 50

5 Development of BURLEY 21, The First Wildfire-Resistant Tobacco Variety, Including Results of Variety Trials

*Howard E. Heggestad, E. E. Clayton, M. o. Neas, and H. A. Skoog

INTRODUCTION

The bacterial leaf spot disease commonly known as wildfire [Pseudomonas tabaci (Wolf & Foster), F. L. Stevens] has been one of the most destructive diseases of tobacco. Wolf and Foster (21) reported that wildfire was first recognized in the United States in 1917 on flue-cured tobacco in North Carolina. The disease has caused severe damage in both plant beds and fields throughout the 8-state burley-producing region, and it has occurred in nearly all other tobacco-producing states. In 1948, Heggestad (9) esti- mated that 75 percent of the burley fields in eastern Tennessee showed some disease and, in the same year, Valleau and Diachun (19) reported the most extensive outbreak of wildfire in Kentucky in 30 years. Wildfire was unusually prevalent in plant beds in Kentucky also in 1950 and 1951 (20). Breeding work to develop wildfire-resistant varieties began at the Tobacco Experiment Sta- tion in eastern Tennessee in 1947. Wildfire continued to be a serious problem in burley tobacco production until 1955, when seed of Burley 21, the first wildfire-resistant variety, was released. Generally, in burley tobacco production, small seedlings in plant beds have been damaged more by wildfire than large plants in the field. Plants of susceptible varieties, depending upon plant size and the severity of attack, may be killed or severely stunted. Disease outbreaks in the field frequently follow transplanting wildfire-infected seedlings. The recommended chemical control measures including treatments with Bordeaux, fixed copper com- pounds, and the antibiotic streptomycin have been of value for disease control in plant beds but not in fields.

*Authors are principal agronomist. Beltsville, Md.: formerly principal pathologist, Beltsville; agricultural aide, Gre.eneville. Tenn.; and research agronomist, Greeneville. All are with the Crops Research Divis"ion. Agricultural Research Service. U. S. Department of Agriculture. 6 Studies on resistance of tobacco varieties and species to wildfire were reported first by Johnson, Slagg, and Murwin (16) in 1924 and by Anderson (1) in 1925. Significant progress in breeding tobacco resistant to wildfire was first reported in 1947 by Clayton (4). He reported that a source of high resistance, "im- munity," to wildfire and blackfire [Pseudomonas angulata, (Fromme & Murray) Holland] was found in the species Nicotiana longiflora C.; the resistance was transferred to a fertile breeding line designated TL 106. This line was obtained as a result of making an interspecific cross and one backcross to tobacco. After a few generations of selfing TL 106, a stable, resistant line was obtained. Planting of TL 106 and hybrids with it and standard burley varieties were made in Tennessee in 1947 and the breeding work to develop improved wildfire-resistant varieties has continued since. In 1955 the breeding line designated Greeneville 25 showed most promise and it was released as Burley 21. Burley 21 was the first wildfire-resistant tobacco variety of any type. In the development of Burley 21, thousands of seedlings from numerous crosses and backcrosses were tested for resistance in plant beds and field plots by inoculations, using sprays containing wildfire-bacteria. Each year hundreds of plants were selected on the basis of resistance and plant type after also inoculating plants in the field plots. Also, each year breeding lines in the F" and later generations were progeny-tested. This was done in replicated plots to determine yielding ability and quality of cured leaf in the absence of wildfire except for occasional natural outbreaks of the disease. Because resistance to tobacco mosaic and black root rot [Thielavi- opsis basicola (Berk & Br.) Farr.] was introduced in the wildfire- resistant breeding material, all promising selections in each generation were indexed to find the selections with combined resistance to the three diseases. This report provides a detailed historical account of the development of Burley 21, the first variety that incorporates wildfire resistance from N. longiflora. Burley 21 was tested as Greene- ville (Gr.) 25 before its release. Heggestad, Clayton, and Felts (13) in 1954 made a progress report on the development of wildfire- resistant tobacco, and Gr. 25 was referred to as the most promising breeding line at that time. In 1955, Heggestad and Clayton (11) published a brief account of the development and release of Burley 21.

7 WILDFIRE, A BACTERIAL LEAF SPOT DISEASE

Identifying symptoms of wildfire are shown in Figure l. At first the lesions are dark-colored. The yellow halos may require 2 or more additional days to develop or about 7 days

Figure 1. Wildfire on burley tobacco leaf. 8 from infection until typical symptoms appear. The lesions may be small or relatively large depending upon the severity of attack. Under conditions of high moisture, the disease may appear as a wet rot causing collapse of entire lower leaves and even death of small seedlings. Under these conditions in plant beds, wildfire has been confused with blue mold. Only on leaves with light infection, as at the middle or upper portion of the plant, do typical individual wildfire lesions with yellow halos develop (Figure 1). Though some other leaf spot diseases affecting tobacco also are characterized by lesions with yellow borders, with wildfire more yellowing develops and a sharp demarcation may be observed between the yellow halo and the normal green of the leaves. With wildfire, the isolated individual lesions are usually round, whereas lesions caused by other disease-producing pathogens tend to be more irregular in shape. The fully-developed lesions may be lh-inch or more in diameter and the original brown or dark centers bleach until they are light grey. A typical disease-infected plant bed (Figure 2) and severe attacks in the field (Figures 3A and 3B) are shown. Buds of some plants show systemic disease development being yellow and stunted. These symptoms resulted from entrance of bacterial toxin into the

Figure 2. Severe wildfire in a tobacco plant bed. Grower had about 1000 square yards of plants in a "new" ground area destroyed by wildfire. 9 A

Figure 3. Severe wildfire development in a tobacco field. A-A relatively early stage, about 1 week after bacterial infection, showing some lower leaves with the leaf spots causing complete collapse. B-A later stage showing stunting as a result of systemic infection ond the loss of severely injured lower leaves is evident. 10 vascular system of the leaf and stem. Usually, systemically- infected seedlings do not recover (Figure 2). However, if wildfire develops in the field after the plants have recovered from transplanting, the systemically-infected plants usually survive but are retarded in growth (Figure 3B). In disease-infested fields the lower leaves with severe leaf spot development shrivel and are lost and yield and quality of harvestable leaves are reduced (Figure 3B). Under relatively dry conditions, attacked seedlings usually recover and lesions are hard to find because infected leaves are lost from the plants. Sufficient bacteria, however, are usually brought to the field on susceptible varieties so that a new attack develops when weather conditions are favorable.

DESCRIPTION OF BURLEY 21 AND HISTORY OF ITS DEVELOPMENT

Burley 21 is a standup variety, holding its leaves more erect than any other variety of burley tobacco (Figures 4 and 5). In leaf number it is intermediate between the high-leaf number variety Burley 1 (10) and such commonly-grown varieties as Burley 2 (12) and Kentucky 16. Relatively few suckers are produced. Because it is a good standup variety, plants of Burley 21 are comparatively easy to cultivate and harvest without leaf-breakage. Plants grow rapidly in the plant beds and are ready to transplant as much as 1 week earlier than plants of other varieties. Burley 21 transplants are characteristically vigorous and usually make very good growth in the field. Studies in South Carolina (7) and un- published reports from Canada indicate that Burley 21 is more tolerant to meadow nematode, Pratylenchus species, than many other varieties. This may account at least in part for early vigorous growth after transplanting. Burley 21 has only a moderate level of resistance to black root rot so that in some seasons, especially on fields in continuous tobacco culture or in rotation with legumes susceptible to root rot, the level of resistance may be too low to produce highest yields. Burley 21 is very resistant to tobacco mosaic. The resistance is of the local-lesion type originally obtained from N. glutinosa L. but transferred to Burley 21 as a result of a cross with Kentucky 56.

Pedigree of Burley 21 The pedigree of Burley 21 (Figure 6) includes an account of 11 Figure 4. Burley 21 tobacco after topping, showing characteristic standup habit af growth in a field near Mountain City, Tennessee. the early breeding work which resulted in the development of TL 106 and later in a number of sister lines designated Gr. 25, Gr. 25A, Gr. 25B, and Gr. 25C. The line tested as Gr. 25 was the progenitor of Burley 21 and it will be frequently referred to in this report. All the Gr. 25 lines originated from Bel 0-22 (50-416), one of several breeding lines tested at Greeneville, Tennessee in 1950. 12 Figure 5. Plant af Burley 21 tobacco in the early bloom stage showing its characteristic habit of grawth.

13 1938 Nicotiana tabacum 4n x N. lon9illora 4n (N. tabacum x N. lon9illora) x N. tabocum BC-l

1942 In the F2 generation the selection TL 106 was made

(In 1945, and also 1946, the F6 lines of TL 106 were tested and all plants remained free of wildlire.)

1945-1949 (TL 106 x Ky. 16) BC2 x Gr. 5) BC3 x Ky. 41A) BC4 x Ky. 56) BC5 x Gr. 18) BC6

Generation 50-416 (Bel-0-22) I I F4 2 3 4 5 6 I T T -r T T (51-421 (Gr 25 in 1951) 51-456 51-457 51-453 51-459 51-460 I iii --r F5 -,--- ~ 1 234 5 1 2 3 1 1 ~~,,~~ ~ t I I t (52-446 447 448 449 450 (Gr. 25 in 1952, Gr.25A (Gr, 25A in 1952 F6 a composite of but discontinued ~~ 52-446 thru 4501 n1ll after 1952 season) Tiin (1 2 3 4 5 1 2 3 4 6 1 2 3 4 5 ITT T T T T T T T T T T T T (Gr. 25 in 1953, (Gr. 25C in 1953 1 15 a composite of a composite of 53-4111:~: :~: i: ;95: F7 53-406 thru 4101 53-424 thru 4231 "T ""~ ","" T a compos ite of 53-411 thru 415) IT'''111 1 ( 1 1 I 2 3 "T T T "T T Tl"""", T (Gr. 25 in 1954, 54-404 405 406 407 (Gr. 25C in 1954, a 54-408 (Gr. 25B in 1954, a composite of composite 0154-404 discontinued after F8 54-400 th ru 4031 thru 407, was dis- 1954) continued after 1954 j~ season) (In 1955 a number of Gr. 25 selections were F9 (composited to form the new variety known (as§~.

Figure 6. Pedigree of Burley and sister lines Gr. 25A, Gr. 25B, and Gr. 25C which were compared with it. All selections and hybrids were critically tested for disease resistance and evaluated for agronomic characteristics. Each year from 1949 to 1955, when Burley 21 was released, about 80 plant selections were progeny-tested in both plant beds and field plots. Each selection to be progeny-tested required at least 2 square yards of plant-bed space with an average of 1,000 seedlings in each plot. The plants were inoculated weekly with bacteria-causing wildfire and 100 to 200 resistant seedlings were pulled for setting in field plots. In this 6-year period, 495 selections required approximately 1,000 square yards of plant bed space and 7.5 acres of field plots to index critically for wildfire-resistance. At least 500,000 seedlings were indexed for resistance to wildfire in the plant beds. About 75,000 of the most vigorous surviving plants were pulled and transplanted to field plots where plants were further tested to determine resistance. The resistant plants with the most desirable agronomic characteristics were tagged and the seed heads bagged to insure self-pollination. In the absence of wildfire inoculations, parallel plant-bed seedings and field plantings were made. This was to determine potential yielding ability and quality of the breeding lines and to select the lines with best agronomic characteristics, especially plant type. The breeding line Gr. 25, which was later released as Burley 21, continued to segregate for wildfire resistance for several generations. The breeding lines which became homozygous for resistance earlier, such as Gr. 26, Gr. 27, Gr. 28, Gr. 29, Gr. 30, and many others, proved to be inferior to Gr. 25 in quality of cured leaf. All but line Gr. 25 were dropped at various stages of development. We believe that Gr. 25 has a smaller chromosome segment from the wild tobacco species than the other breeding lines. Conse- quently, the segment which carries wildfire resistance has become relatively free of undesirable linkages detrimental to quality. The resistance of Burley 21 to wildfire was very high after completion of tests in 1954. Burley 21 (Figure 7A) developed no wildfire in a plant bed where plants of Burley llA (Figure 7B) were nearly all killed after a natural outbreak of the disease. In 1957, a few wildfire-susceptible plants were found and removed from the foundation seed stock. Since 1957 there have been several critical tests for wildfire-resistance. Very few additional susceptible plants were found. In the tests conducted by Garber and Heggestad (6), Burley 21 was highly resistant. In these tests the 15 A

Figure 7. Compo rison of wildfire resistant and susceptible varieties in the same plant bed: A, Burley 21 plants making good growth and free of wildfire; B, Burley 11A plants stunted or destroyed by wildfire following a natural outbreak of the disease. Mountain City, Tennessee, May 1B, 1954.

16 bacteria were washed to remove accumulated toxin before making the plant inoculations. Burley 21 has been used in many crosses as a source of wildfire and mosaic resistance; for example, when combining resistance to these diseases with resistance to black shank [Phytophthora parasitica Dast. val'. nicotianae (Breda de Haan) Tucker] and fusarium wilt [Fusarium oxysporum Schlect f. nicotianae (J. John- son) Snyder & Hansen] from Burley llA and Burley llB. Wild- fire resistance is controlled by a single pair of dominant genes (5). In F~ populations involving resistant and susceptible parents, excellent fit to the simple ratio of three resistant to one susceptible plant was observed.

Procedure for Testing for Wildfire-Resistance and Yield and Quality Progeny of each selection was indexed for wildfire resistance in the plant beds. Seedings were made in boxed 2-square yard plots. After the inoculations with wildfire bacteria, most or all of the plants in plots of susceptible varieties used as checks were killed. After resistance was stabilized, as in the original resistant parent TL 106 (see pedigree Figure 6), no plants were killed by wildfire as determined by actual plant count before and after inoculation in marked 2-square foot areas of each plot. Weekly spray inoculation~ were made with wildfire bacteria for 5 to 6 weeks from the time the stands were established and plants were in 2- to 4-leaf stage until about 2 weeks before transplanting. About 2 gallons of inoculum were required to secure uniform coverage of the total plant bed area used for these studies, which was about 160 square yards each year (Le. about 80 selection or plots, with 2 square yards for each). The spray contained 1,000 ml. of a bacterial culture grown on potato-dextrose broth in each gallon of water. About 6 liters of culture medium were prepared at a time. Half-gallon Mason jars plugged with cotton to prevent contamination were suitable containers for a liter of the culture medium. Each jar was seeded with about 5 ml. of bacterial inoculum from a test-tube culture. The larger cultures were used immediately after about a 4-day incubation period or stored in a household refrigerator. The bacterial spray was applied with a hand-operated 3-gallon sprayer relatively early in the morning, when leaves were wet 17 by an evening shower or heavy dews. Early in the morning under moist conditions, lower leaves of susceptible plants would frequently show internal water congestion (8). Severe disease development on susceptible plants usually followed the first inoculations (Figure 8-also cover photo). After later inoculations, leaves of surviving susceptible plants developed wildfire lesions. Any susceptible plants showing leaf spots were avoided when plants were pulled for field transplanting. In an especially dry season, disease development was not as critical as in wet seasons and a few susceptible plants escaped infection in the plant bed or the disease was not detected when plants were pulled. At weekly intervals field inoculations were made by the procedure described for plant beds. In some seasons, no further disease development occurred except in rows of susceptible check varieties. Field plot size was 1/200-acre, or in a 50-plant row with plants 15 inches apart in rows 3V~ feet apart. Replications varied from two to four in different tests, depending on interest in the specific selections and the amount of plot area available. Advanced selections were seeded also in uninoculated beds to obtain plants for yield and quality evaluation. Critical information on these agronomic characteristics could not be obtained in plantings where plants were tested for wildfire and tobacco mosaic resistance and varying numbers of plants were selected and bagged to obtain seed. For the yield and quality evaluation, the field plots were 1/200-acre with 3 or 4 replications except for the most advanced uniform variety trials conducted at about 10 locations each year; for these, 1/100-acre plots and four replications were used. The procedure for yield and quality testing was the same as described for the black shank-resistant varieties Burley llA and llB (14). Values for smoking tobacco in the tables include all X, C, and BF grades. In several tables a grade index is used to indicate grade quality rather than price per hundredweight or in addition to information on price. The average grade index is computed after assigning index values for each grade of tobacco. The indices are based on average prices of each tobacco grade for 1934, 1935, 1937, 1938, 1939, and 1940 crops. The index values ranging be-

Figure 8 (See cover poge). Compo rison of a wildfire-susceptible burley variety of tobacco in the plot on the left with a wildfire-resistant variety. All plants were 'inoculated about five times at weekly intervals. Most susceptible plants died after they developed disease so the plant stand was reduced. 18 tween 0 and 1 were computed for each grade by comparing all grades with elL, the highest grade with a value of 1. As with dollar value per acre, the crop indices were obtained by multiplying the grade index value and yield in each replication. Burley 1, Burley 2, and Kentucky 16 were used for several years as standards of comparison in tests with the new breeding lines. Summary data on their performance in 45 replicated variety tests in 6 years are presented (Table 1). Highest yield and value per acre were obtained with Burley 2. The value per acre of Burley 2 was $12 more than for Burley 1 and $36 more than for Kentucky 16. Burley 1 produced the best quality tobacco as shown by average price per hundredweight. The advanced breeding line Gr. 25, progenitor of Burley 21, was tested most extensively in 1951, 1952, and 1953. As a standard of comparison for other data on varieties and breeding lines, the variability in yield, price, and value per acre-which may be attributed to seasons-is shown (Table 2). These data are from the same tests used in making up Table 1. The data for each year were obtained by averaging the data on the varieties Burley 1, Burley 2, and Kentucky 16 from 8 to 10 variety tests. In this 6-year period, highest yields were produced in 1948 and lowest yields in 1949. In 1952, a very dry growing season, yields per acre were low for all varieties. Best quality was produced in 1951, as indicated by greatest percentage of smoking tobacco and the price per hundredweight.

Agronomic Results with Breeding Lines and Varieties, 1950

The breeding line 50-416 in F4 generation, progenitor of Gr. 25 (Burley 21), is compared in Table 3 with the standard varieties

Table I-Average results from 45 replicated burley tobacco variety tests in Tennessee, 1948 through 1953, comparing Burley 1, Burley 2, and Kentucky 16 in yield and grade quality.

Smoking1 Price2 Value Variety Yield tobacco $/acre Lb./acre $/cwt. 1070 1942 1439 55.19 Burley 1 1082 2017 1367 53.39 Burley 2 52.90 1046 Kentucky 16 1969 1331 1. AU X. C. and BF grades were included. 2. In each year the price is based on the g'eason's average prices on all markets. 19 Table 2--Six years' data c011lparing tobac('() yields and grade quality tor different seasoNS, arranged ill descending order from high to loll' Faille per acre '.

---~--_._-- -_ ...._~._ ..~- . ------Smoking2 Yeor Yield PriceJ Volue tobocco ------'-,.,_ ..---'------. -,------,.------,'.------.-._---- Lb./acre Percent $/cwt. $/acre 1948 2434 76.5 51.20 1251 1953 2036 67.4 56.27 1156 1951 1922 80.8 59.76 1144 1950 1888 72.1 56.30 1071 1952 1829 53.1 50.99 920 1949 1746 69.1 48.44 852

1. Data are avC'rag'(' vaha's for Hurley I. Hurley 2. ann KC'ntucky 111 in replicRterl variety test~. Results were from 8 to 10 locations in TenneSR('(' each year. 2. All X, C. ami RF' g'raoC's were inclurlerl. :3. In eaeh year the price is based on the seRSOn'F! Rverage price!" on all burlC'y markelR.

TaMe 3-Yield m/(l grade If/fIllit y of resistmlt tof1l1CCOhrecdillg lim's follow i/lg set'eral irwcltlatiOlIS of the plants with wildfire hacteria, 1950'. ---_._._-- Line or Smoking Yield GradeJ Crop4 Price Value variety tobacco

Lb'/acre Percent2 Index $/cwt. $/acre 50-401 1721 90.1 .702 1206 60.49 1040 50-403 1742 85.6 .743 1295 60.71 1057 50-4046 2038 89.7 .731 1485 60.80 1238 50-4056 1829 85.3 .730 1329 60.12 1097 50-406 1986 84.1 .727 1443 60.29 1198 50-4076 2362 81.3 .727 1713 59.69 1408

50-4086 2408 77.5 .678 1636 57.75 1392 50-410 1890 91.6 .797 1507 62.31 1178 50-4116 1803 98.4 835 1515 63.26 1142 50-412 1652 87.4 .699 1154 59.38 981 50-415 1996 82.9 .752 1501 60.43 1206 50-4165 6 2124 92.2 830 1764 62.95 1337

50-417 2084 78.6 664 1388 58.11 1210 50-4376 2091 84.2 .726 1518 60.26 1261 50-4396 1918 87.4 829 1588 62.24 1194 50-441 1978 75.8 .694 1369 58.60 1158 Kentucky 16 2074 86.2 .750 1550 60.85 1260 Burley 1 1902 88.9 .759 1443 61.22 1164

1. Results bas eo on 50-plant plots. two repli('ation~. 2. Included all X. C. and BF grades. a. Based on average priceR of tobacco grades for In:H. 1930, 1na7. In3~. Inan. a.,nd 1!J40 crops. Index values rang-ing between 0 and 1 were computed for each ,graoe by comparing: all grades with Cl L. the highest grade with value of 1. 4. Crop index obtained by multiplying the grade index value and yield in each replication. 5. Progenitor of Burley 21 selection designated Gr. 25 in 1951. 6. Advanced a generation and continued in 1951. 20 Burley 1 and Kentucky 16, and with 15 of the 51 wildfire-resistant lines tested in 1950. In this series, 50-416 rated third in acre-yield and acre-value, second in price per hundredweight, percent smoking tobacco, and grade index and first in crop index. Under the conditions of the test 50-416 was superior to the two standard varieties in both acre-yield and quality of cured leaf. In this early generation the line 50-416 produced a high proportion of cured leaf classified as "cutter" grades, which normally bring better prices than "flyings" or "leaf" grades. A few wildfire-resistant lines were included in the 1950 uniform variety tests conducted at branch experiment stations in Tennessee and at farm locations, but the breeding line 50-416 was not included until the following year when a selection in it was designated Gr. 25.

Agronomic Results with Breeding Lines and Varieties, 1951 In 1951 five breeding lines designated Gr. 25, Gr. 26, Gr. 27, Gr. 28, and Gr. 29 were selected for test in the uniform variety trials conducted at 10 locations in Tennessee. Selection number 1 of 50-416 (Table 8) was designated Gr. 25. Gr. 26 was a line with breeding similar to Gr. 25, being a composite of selections 2, 3, and 4 in 50-407 (Table 3). This line had the highest acre- value in 1950. Gr. 27 was from a cross (TL 106 x Ky 16 x Gr. 5 x Ky 41A) x (TL 106 x Ky 16 x Gr. 10 x Ky 56 x Burley 1) being a composite of three selections in 50-408, the highest yielding line in Table 3. Gr. 28 and Gr. 29 were two additional lines with the same pedigree as Burley 21, but separated from it before the

F 1 generation. Of the nine entries in the 1951 uniform variety tests (Table 4), Gr. 25 was first in grade index at 7 locations, second at 2 locations, and third at the other location. It had the highest average crop index for the 10 locations. The average yield for Gr. 25 was lower than that for all except one of the experimental breeding lines, but it was about the same in yielding ability as Burley 1 and Ken- tucky 16. Data on cured leaf including nicotine content are provided (Table 5). In this series, the line designated 51-421 (Gr. 25, or Burley 21) rated fourth highest in grade-index value and second in percent of production included in better smoking tobacco grades. It had the highest percentage of nicotine in the series. Line 51-419, one of the selections which was composited to make Gr. 26, produced the highest crop-index value. In the group B series (Table 6), 21 Table 4-Disease resistance and summary of cured-leaf data on tobacco breeding lines and varieties at 10 locations in Tennessee, arranged in descending order according to crop index 195P.

Line Resistance to Yield Smoking tobacco Grade2 Crop2 or Black Tobacco Wildfire Lb./acre Percent Lb./acre index index variety roat rot mosaic

Greeneville 25 good good very 1909 83.1 1571 .709 1349 (Burley 21) (segregating) good Greeneville 17A good 1957 85.1 1668 .683 1343 Burley 2 good 1973 81.8 1589 .671 1303 Greeneville 26 fair very very 1982 79.7 1578 .640 1268 good good ~ ~ Burley 1 very 1891 81.2 1517 .667 1248 good Greeneville 29 good very very 1950 77.7 1513 .640 1246 good good Kentucky 16 good 1903 79.5 1479 .642 1203 Greeneville 28 good very fair 1886 73.0 1371 .620 1176 good (segregating) Greeneville 27 good very very 1992 70.1 1388 .578 1148 good good

1. Data based on four replications, 1/100-acre (100 plant) plots at each of 10 locations; C. Bettis, Loudon County; H. Gaby, Greene County; W. Mitchel, Jefferson County; W. Owens, Cocke County; F. Rupe, Washington County; H. Rutherford, Sullivan County; H. Sloan, Smith County; Middle Tennessee Experiment Station, Columbia; Plateau Experiment Station, Crossville; Tobacco Experiment Station, Greeneville. 2. See footnote 3 and 4, Table 3. Table 5-Yield and grade quality of resistant tobacco breeding lines following several inoculations of the plants with wildfire bacteria, Group A 1951'.

Line or Smoking Nicotine Family Yield Grade2 Crop2 variety tobacco content

Lb./acre Percent Index Percent3

51-401 1436 87.8 .638 930 4.10 51-402 1416 86.6 .682 982 3.96 51-403 1210 87.5 .647 777 4.26 51-404 1004 82.4 .587 590 4.19 51-405 50-416 1294 86.4 .725 946 3.81 51-406 Gr. 28 1296 84.6 .608 777 4.49

51-407 Gr. 28 1411 80.0 .619 878 3.67 51-408 1008 86.9 .591 599 3.94 51-409 1393 82.5 .663 936 4.47 51-410 Gr. 29 1392 86.5 .666 947 4.38 51-411 Gr. 29 1540 83.6 .689 1066 3.45 51-412 Gr. 29 1527 83.3 .628 1006 3.85

51-413 1576 84.4 .688 1078 3.83 51-414 1743 84.9 .675 1186 4.18 51-415 1400 81.8 .635 907 3.95 51-416 1449 86.5 .720 1049 4.31 51-417 1292 78.5 .599 790 4.14 51-418 Gr. 26 1254 85.7 .631 801 4.11

51-419 Gr. 26 1699 86.0 .723 1231 4.41 51-420 Gr. 26 1136 83.9 .589 674 4.28 51-421 Gr. 254 1279 89.8 .716 847 4.71 51-422 Gr. 27 1419 70.6 .571 820 4.16 51-423 Gr. 27 1250 77.4 .555 694 4.41 51-424 Gr. 27 1305 79.0 .569 761 3.49

51-425 1430 80.5 .629 936 3.71 51-426 1565 80.9 .599 955 3.84 51-427 1317 86.2 .676 906 2.38 51-428 1450 85.1 .675 985 2.64 51-429 1323 86.5 .646 860 2.49 Burley 1 1493 90.5 .691 1031 3.96 Kentucky 16 1298 85.9 .630 829 4.06

I. Three replications, 50-plant plots. 2. See footnotes 3 and 4. Table 3. a. Data are the averages from two replications; samples consisted of all tobacco in the third (cutter) farm grade from 15 plants taken at random from the 50-plant row plots. Analysis by D. R. Bowman, plant physiologist, Crops Research Division, Agricultural Re- search Service, U. S. Department of Agriculture. Knoxville, Tenn. 4. Progenitor of Burley 21. 23 Table 6-Yield and grade quality of resistant tobacco breeding lines following several inoculations of the plants with wildfire hacteria, Group B 1951',

------_ ..------_._------_._-----~._-- ---_.~--_. __ .--- .------Nicotine3 Line or Smoking Grade2 Crop2 Yield tobacco content Yoriety --_ ...... • _--~ ------_._---_ ..------__._--_._

Lb./acre Percent Indell Percent 2.47 51-430 1622 57.9 .573 914 2.08 51-431 1767 76.2 .655 1161 2.54 51-432 1532 60.7 .548 838 2.35 51-433 2010 42.5 .580 1162 231 51-434 2175 79.2 .642 1397 1.98 51-435 2122 65.4 .652 1389

2.52 51-436 2395 67.1 .651 1567 2.15 51-437 1716 87.9 .698 1204 1.81 51-438 1958 69.3 .652 1268 2.31 51-439 2016 49.8 .591 1189 3.20 51-440 2043 83.1 .655 1337 3.14 51-441 1874 81.5 .686 1280

3.16 51-442 1847 64.6 .640 1161 3.56 51-443 1664 85.3 .720 1187 3.44 51-444 1832 87.8 .728 1333 51-445 1558 84.8 .724 1128 51-446 1472 82.8 .716 1054 3.96 51-447 2078 81.4 .652 1355

345 51-448 2197 85.1 .673 1492 3.52 51-449 1956 85.0 .677 1316 3.30 51-450 2144 79.5 .614 1310 3.50 51-451 2138 68.6 .620 1314 3.52 51-452 2552 67.0 .638 1631 365 51-453 2097 64.3 .594 1254

3.89 51-454 2073 77.5 .678 1402 3.79 51-455 1867 78.4 .725 1355 4.14 51-4564 2028 79.8 .728 1483 4.26 51-4574 1830 78.3 .732 1340 .765 4.07 51-4584 2136 87.6 1633 3.58 51-4594 1941 871 .756 1467

3.86 51-4604 1846 85.6 .778 1435 .702 3.84 51-4614 1776 85.0 1251 2.74 51-462 1797 80.1 .677 1219 .708 2.25 51-463 1948 88.2 1381 2.44 51-464 1819 84.7 .712 1295 3.62 Kentucky 16 1466 84.6 .660 967

24 Table 6-Continued

3 Smoking Nicotine Line or Grade2 Crop2 Yield tobacco content variety ------_. __ .._._~... __ ._- -- ~_ .._~~_..--~ ..._---_.~--_..._~.-~._.~- Percent Lb./acre Percent Index

81.6 881 3.23 Burley 1 1441 .608 .652 930 360 Burley 1 1441 89.6 .789 1248 51-466 1582 95.3 .700 1135 51-467 1622 92.9 .653 973 51-468 1490 93.8 .540 802 51-469 1486 96.3

687 1096 51-470 1596 92.9 675 1092 51-471 1618 85.7 .719 1565 51-472 1642 95.3 .718 975 51-473 1358 94.7

1. Two replications. 50-plant. plot~. 2. See footnotes ~ and 4. TaLII!' :~. a. See fuotnote 2. TaLle 5. 4. Sister plant ~elt'dions f.'om f)O-416 \GI'. 25). Rplp(,tions from 51-458 Wf'l'e tested in 1952

ft:-i Gr. 25A. 51-458 produced the highest crop index. Lines 51-456 through 51-461 and 51-421 (Gr. 25) were sister-plant seleetions. All produced high grade indices with 51-460, -458, and -459 rating second, third, and fourth, respeetively, in value for the series. Lines 51- 427 through 51-439, and 51-462 through 51-464, were relatively low in nicotine (5), but study of later generations indicated that they produced relatively high levels of nornicotine and they were comparable with other lines in total alkaloid content. These low- nicotine lines were discontinued because it was discovered, in cooperative studies with The American Tobacco Company, reported by Moseley (17), that poor smoking charaeteristics were associated with high nornicotine content.

Results of Yield and Quality Tests Conducted with Susceptible and Resistant Tobaccos in Presence of Wildfire and Tobacco Mosaic Most of the wildfire-resistant lines also had combined re- :'\istance to tobacco mosaic of the local-lesion type from N. glutinosa. In 1951 experiments were initiated to determine the relative produetion performance of resistant breeding lines such as Gr. 25, Gr. 26, and Gr. 27 and standard susceptible varieties in presence of these diseases. The tests were conducted at the Tobacco Experi- ment Station and also at the R. Link farm, Greeneville, Tennessee. At the latter location in the 1950 season wildfire and blackfire 25 caused severe losses to the crop. In these experiments, the plants were inoculated with tobacco mosaic virus on July 3, about 5 weeks after transplanting. At this time the plants were making rapid growth after recovering from transplanting, being 1 to 2 feet in height. Also, beginning early in July and continuing at approximately 10-day intervals, wildfire inoculations were made by spray- ing a water suspension of bacteria on the plants as described previously when tests for resistance to this disease were made in the plant beds. Burley 1 and Kentucky 16 were included as susceptible checks with plants in some plots of each variety inoculated to produce both wildfire and mosaic and in other plots inoculated only with wildfire bacteria.

The breeding line Gr. 26 and a sister line 51-451 produced the highest crop-index values (Table 7). A value for crop index is comparable to dollars per acre. The differences between Gr. 25 (Burley 21) and Gr. 26 in values for crop index and the other characteristics were not statistically significant. Gr. 25 produced the best quality cured leaf as indicated by grade indices and the yield of tobacco in best smoking grades. The yield, grade, and crop indices for the susceptible varieties Burley 1 and Kentucky 16 were much lower than those for Gr. 25 (progenitor of Burley 21). The values for Gr. 25 and the susceptible varieties were significantly different as revealed by the L.S.D. values in Table 7. The yields of the two check varieties averaged only 54 percent of the Gr. 25 yield when the plants of all varieties were inoculated with wildfire bacteria and tobacco mosaic virus (Figure 9). When plants were inoculated only with wildfire bacteria, the yields of the check varieties were about 84 percent of the yield of Gr. 25. The grade-index value of check varieties was reduced to about 60 percent of Gr. 25 indices when plants of the check varieties were infected with both diseases and to 67 percent of Gr. 25 indices when infected only with wildfire bacteria. The differences in cured-leaf quality between the two susceptible varieties Kentucky 16 and Burley 1 inoculated with only wildfire bacteria were highly significant. Although the quality of Burley 1 was much better than that of Kentucky 16, the yields of the two varieties were about the same when only wildfire was present.

At the Link farm (Table 8), as well as at the Tobacco Ex- periment Station (Table 7), the wildfire- and mosaic-resistant lines were superior to Burley 1 and Kentucky 16 when wildfire only was present or in the presence of both diseases. Because transplants 26 Tahle 7- \Vildfire- and mosaic-resistant lines compared with susceptihle tohacco varieties under severe disease conditions, Tohacco Experiment Station, 195P.

3 Crop3 Plants Yield Smoking tobacc02 Grade Breeding line average Lb./acre -- Perc-;;;t---Lb./acre index index or variety number ------88.3 1951 .703 1370 Greeneville 254 50 1950 (50-416-1 ) 78.6 1346 .640 1087 51-459 46.5 1697 (50-416-5) 79.1 1691 .689 1469 Greeneville 26 48.3 2127 (50-407 -2, 344) 76.3 1704 .637 1426 51-451 48.0 2241 (50-407 -9) 50.8 963 .568 1076 Greeneville 27 48.5 1896 (50-408-0, 2 and 3) 61.0 1193 .575 1128 51-425 49.5 1960 (50-408-00 ) 65.9 1010 .524 829 Greeneville 285 49.0 1570 (51 -406 and 407) 67.9 1459 _649 1402 51-413 48.8 2161 (Gr. 26 selection) 81.8 757 .424 393 Burley 1 48.5 925 77.7 1258 .534 867 burley 16 49.8 1633 37.9 455 .411 488 Kentucky 16 49.0 1189 35.9 657 .411 677 Kentucky 166 47.3 1647 196 L.5.D. at 5-percent level 249 18.4 320 .065 .087 263 L.5.D. at 1-percent level _-334 24.7 432 347 L.5.D. at O.l-percent level - .438 32.6 564 .115

1. Data based on four replieations. 50-plant (1/Z00-acre) single-row plots. 2. Includes all X. C. and III' grades. 8. See footnotes 3 and 4, Table :~. 4. Progenitor of Burley 21. 5. Segregating for mosaic resistance. 6. Not inoculated with mosaic, remainder of vlots inoculated July :~; plants in all plots were inoculated with wildfire ba(.teria at nho\1t 10-duy intervals dul'ing the growing sem~on.

were poorer, the stands of some breeding lines were reduced more than those of the susceptible varieties. Transplants of the susceptible varieties were from a plant bed at the Tobacco Experiment Station because in the bed at the field site they were stunted as a result of wildfire which developed without inoculation. The average yields of the check varieties at the Link farm were 81 percent of Gr. 25 (Burley 21) yields when plants were inoculated with only wildfire bacteria, and 62 percent when they were inoculated with both wildfire bacteria and tobacco mosaic virus. The 27 Figure 9. Row plots at Experiment Station inoculated with both tobacco mosaic virus and wildfire bacteria. On left, Kentucky 16 and right Gr. 26, susceptible and resistant, respectively, to both pathogens.

combined average grade index values for the check varieties Burley 1 and Kentucky 16 were reduced to 72 percent of the value for Gr. 25 when only wildfire was present and to 65 percent of the Gr. 25 value when in presence of both diseases. These values compare with 67 and 60 percent of Gr. 25 values at the Experiment Station location. The yields of the two check varieties (Table 8) were about the same in the presence of wildfire or of both diseases; however, the quality of leaf of Kentucky 16 was poorer than that of Burley 1. Differences in plant growth of resistant and susceptible varieties after inoculation with tobacco mosaic virus and also wildfire bacteria are shown in Figures lOA and lOB. Figure 10C shows effect of inoculating plants of the susceptible variety with only wildfire bacteria.

Resistance to Blackfire (Angular Leafspot) At the Link farm in 1950 a severe outbreak of blackfire, as well as of wildfire, was noted. Resistance to blackfire, as well as wildfire, may be expected because the bacteria causing these two diseases are indistinguish- 28 Table 8-Wildfire- and mosaic-resistant lines compared with susceptible tobacco varieties under severe disease conditions, R. Lin"/?Farm, 195P.

Plants 3 Grade· Crap· Line or Yield Smoking tabacca variety2 average Lb./acre Index Number Lb'/acre Percent 911 85.2 1309 .595 255 94.3 1534 Greeneville 1198 .599 859 89.3 1438 83.3 51-459 1123 .569 848 26 87.3 1487 75.1 Greeneville 1429 .647 1106 94.3 1710 83.5 51-451 993 .526 786 27 93.7 1491 65.8 Greeneville 1229 .585 979 97.0 1664 72.9 51-425 .482 609 64.6 816 286 95.3 1262 Greeneville 1297 .554 1025 97.0 1709 74.7 51-413 653 .409 509 99.3 965 67.6 Burley 1 846 .458 596 j7 100.0 1297 65.0 Burley .361 354 991 50.9 509 Kentucky 16 96.3 .401 483 49.6 598 Kentucky 167 99.0 1205 (1/100 acre). 1- Data based on three replications, four 25-plant, single-row plots 2. Entries the same as in Table 7, 3. Includes all X, C, and BF grades. 4. See footnotes 3 and 4, Table 3. 5. progenitor or Burley 21- Segregating lor mosaic resistance. 6. Not inoculated with mosaic, plants in remainder or plots inoculated July 3; plants in all 7. plots inoculated with wildfire bacteria at about 10-day intervals during the growinlr season.

Figure 10A. Kentucky 16 plants in 4-raw plot of tobacco infected with tobacco mosaic and wildfire. 29 Figure lOB. Plants af a wildfire- and tobacco mosaic-resistant breeding line (Gr. 26) inoculated with the causol organism of both diseases ot -the same time as plants of Kentucky 16 in Figure lOA. Leof spot on lower leaves is Cercospora, "frog-eye:'

Figure 10C. A 4-row plot of Kentucky 16 tobacco showing effect of wildfire without tobacco mosaic. 30 A

Figure 11. A, Plants of a susceptible variety of tobacco with blackfire which appearr.d after transplanting and. B, Plants of Burley 21 were free of blackfire in the same plant bed indicating possible resistance also to this disease. link

farm, 1951.

31 able except for differences in toxin production and consequently in the appearance of symptoms (3). In addition, TL 106, which is the source of wildfire resistance in Burley 21, was found to be resistant to black fire (4). Because blackfire has been observed only rarely in recent years in the burley-producing area, critical tests to determine resistance of Burley 21 have not been eonducted. In one case blackfire did not develop on Burley 21 seedlings in a plant bed but it developed on plants of a susceptible variety (Figures 11A and 11B). In recent years we have evidence of blackfire on field plants of Burley 21. Critical studies are needed on resistance to black fire of Burley 21 and other wildfire resistant breeding lines.

Agronomic UesuIts with Breeding Lines and Varieties, 1952 The wildfire- and mosaic-resistant lines Gr. 25, Gr. 26, and Gr. 29 were tested again in 1952 in the uniform variety trials. A sister selection of Gr. 25 in the F;, generation, 51-458 (Table 6), was designated Gr. 25A and also included in the trials. Gr. 27 and Gr. 28 were not included because of inferior grade quality in the 1951 variety trials (Table 4). Because of the dry season in 1952, yields (Table 9) of all varieties were much lower than in 1951 (Table 4). Performance of Gr. 25 was satisfactory; however,

Tallie 9---511 'ILl/wry of cured-leaf data Oil tobacco IJrecdillg lillc~ mILL l'arietic.' at eight locatioll~ m Tel1/'IC~.,ec m 1952'. --- -.---. ---- s-",,·o-ki;;g2· Variety Yield GradeJ CropJ Price Value tobacco -_._------~---_.~---~---~------~._--_._---_.------, ------Lb./acre Percent Index $/cwt. $/acre Gr, 25 (Burley 21 ) 1761 59.4 .498 873 53.26 928 Gr. 25A 1686 54,9 504 836 Gr, 26 1887 54,0 .459 871 50,54 949 Gr, 29 1747 43.4 .437 765 Gr. 41 1673 642 516 848 53,93 884 Gr, 42 ( Burley 11A) 1811 68,1 .536 955 54,98 981 Burley 1 1763 59,7 .477 828 52,73 917 Burley 2 1901 47,6 .468 880 50,33 944 Kentucky 16 1823 52.2 .464 836 49,91 900 .. ------_."._._._-_ ..__ ._--- LSD. at 5-percent level 128 9,2 ,040 103 2,53 46 LSD. at I-percent level ___170 12,2 ,053 137 3,36 61 ------~-_. __ .~_._------_._,._. _ .. -.. _-~------_._---- 1. Variet.y t{"Rt~ were conducted at: Tohaec(} ~:xpC'rim(>nt St.ation. Grecneville; Plateau Experiment Station, Crossville; Highland Rim Experiment Station, Springfield; Middle Tennessee P~xperiment Station, Columbia; W. A. Owens, Cocke County; H. Gaby, Greene County; H. Moser, Jefferson County; H. F. Sloan. Smith County. 2. Includes all X. C. and BF grades. 3. See footnotes 3 and 4. Table 3. 32 performance of Burley 11A during the dry season was very good, significantly better than that of Kentucky 16 in all comparisons except yield. The values for Burley 11A were higher in all comparisons than those for Gr. 25, but the differences were not large enough to be statistically significant except in value per acre. Gr. 25A was poorer than Gr. 25 and the difference in yields between it and Kentucky 16 was significant.

Tal?le 10- Yield alld grade Ifllality of resistmlt tohacco hreeding lines follow- illg sel'eral inoclllatirms of tlze }Jlmlts with wildfire bacteria, 1952'.

Group and line Plant Yield Smoking tobacco Grade2 Crop2 of voriety stand Lb'/acre Percent Lb./acre Index index ------Group A 52-4463 42 1787 58.9 1027 581 1027 52-4473 47 1996 55.8 1108 522 1051 52-4493 50 1893 59.4 1097 .569 1080 52-453 49 1983 61.7 1255 .538 1067 Kentucky 16 49 2111 53.4 1131 .519 1095

Group B 52-4483 44 1945 66.4 1299 558 1086 52-4503 46 1996 62.6 1232 .488 972 52-452 48 1826 66.8 1226 .508 930 Kentucky 16 48 2051 50.9 1027 .425 867

Group C 52-454 47 2119 183 384 .453 957 52-455 50 2046 52.6 1075 .526 1050 52-456 50 2252 45_2 1018 469 1056 52-457 52 2268 30.2 674 .471 1063 52-458 45 1925 50.9 981 .542 1044 52-459 51 2204 45.2 997 .433 953 52-460 47 1868 67.3 1256 .508 942

52-461 51 2227 33.1 735 463 1031 52-462 47 2040 43.1 880 471 961 52-463 47 2284 49.3 1127 .500 1137 52-464 45 2135 44.2 938 .486 1039 52-465 46 2271 52.8 1198 .493 1115 52-466 48 1943 18.7 365 .470 918 Kentucky 16 47 2168 55.2 1202 .447 965

1. Three replicationR of each group (A, R. and C). Lines were randomized in different blocks because plants of different lines were ready to transplant at somewhat earlier dates. Group A was transplanted first and group Clast. 2. See footnotes 3 and 4, Table 3. 3. Lines l'ompositcd to make liP Gr. 25 proR'enitor of Burley 21 in 1952. 33 A

Figure 12. Tobacco plants shawing symptams of a disease apparently caused by a strain of Phytophthora parasitica. A, Light-colored and diseased plant in center 'foreground. B, Stem canker in region of adventitious roots on diseased plants as in A. Pith area of the stem was usually affected. The disease often attacked primary roots. A strain of Phytophthora was frequently isolated from advancing margins of the diseased areas. 34 Burley 21 in 1952 was tested as Gr. 25, and it was a composite of 52-446, -447, -448, -449 and -450, being five individual plant selections from 51-421. Progeny testing of the five selections showed very little difference in yielding ability and quality (Table 10). Two of the five lines were apparently homozygous for resistance to wildfire and one of these, 52-449, was selected to con- tinue the breeding line Gr. 25 because of somewhat better grade quality.

A "New" Disease Attacks some Wildfire-Resistant Breeding Lines

The poor performance of Gr. 25A was due largely to its extreme susceptibility to a disease (Figures 12A and 12B) which, according to identification of several fungus isolates and other studies, might have been caused by a species of Phytophthora. Although the fungus appeared to be a strain of P. parasitica var. Nicotianae which causes black shank, attempts to reproduce the disease by inoculation were not successful. Comparisons of susceptibility of strains and varieties at the Mills farm near Loudon, Tennessee, and at the Moser farm, Jef- ferson County, are shown in Tables 11 and 12. At the Mills and Moser farms, 45 and 21 percent, respectively, of plants of Gr. 25A were killed by the disease. At the Mills farm almost three times as many plants of Gr. 25A as of any other strain or variety,

Table Il-Resl)onse of to]1acco varieties to a stalk and root disease first observed in 1952, 1\1ills Farm, L(l11don, Tennessee\

Diseased plants in 100-plant plats in replicatian --~-_.~--~ Variety 2 3 4 Av.

Gr. 25A 39 39 53 47 45 Gr. 26 15 21 28 3 17 Gr. 25 (Burley 21) 17 20 25 2 16 Gr. 29 8 5 22 15 13 Gr. 42 (Burley l1A) 0 0 7 4 3

Gr. 24 (Burley 2) 1 0 1 0 0.5 Gr. 41 0 0 0 0 0 Burley 1 0 0 0 0 0 Kentucky 16 0 0 0 0 0 1. Observation~ made June :~O. 1952; Disease helipved caused by a strain of Phytophthora paralJitica val'. nicotianae. 35 Table 12-Response of vanetleS to a stalk and root disease first ohserl'ed in 1952, Moser Farm, Jefferson Counti·

Diseased plants in 100-plant plats in replication ------Av. 2 3 4 Variety -----_._--- _._.--- 19 21 16 18 32 Gr. 25A 2 4 5 4 5 Gr. 26 4 4 3 4 3 Gr. 25 (Burley 21 ) 2 0 2 6 1 Gr. 29 1 03 0 0 0 Gr. 42 (Burley l1A) 0 0 0 0 0 Gr. 24 ( Burley 2) 0 0 0 0 0 Gr_ 41 0 0 0 0 0 Burley 1 0 0 0 0 0 Kentucky 16

1. Believed ('au~ed by a strain of Phytophthora parasitica.

were diseased, and at the Moser farm about five times as many plants of Gr. 25A were diseased. No plants of Burley 1, Kentucky 16, and Gr. 41 were diseased at either location. Because of its greater susceptibility, Gr. 25A was not included in tests in 195B except where studies were made to check further on the disease. A farm location was selected in 1953 to test a number of selections which had shown susceptibility to the stalk and root disease first observed in 1952. The Mills location was not available: however, about 21j:! acres of the Hashe farm, Greeneville, Tennessee, were obtained. Plots were located in a field which was in tobacco in 1952. Enough diseased plants were present in the field in 1952 to result in severe losses of susceptible strains in 1953 if black shank in its usual form was present in the previous year. The disease did not appear in 195B on Gr. 25A selections or on any other strains at this location. A few diseased plants of Gr. 30 lines were found at the Owens and Moser locations in 1953. The stalk and root disease affected plants of Gr. 25A at both of these locations also in 1952. Yields of Gr. 25A were lowest of all entries at the Moser and Owens farm in 1952 (Table 13). At the other farms, yields of Gr. 25 (Burley 21) and Gr. 25A were more nearly the same.

Agronomic Results with Breeding Lines and Varieties, 1953 During 1953, which was a very dry season (similar to 1952) at Greeneville, Tennessee, and elsewhere throughout the State, 36 Table 13-Yield per acre of burley tobacco varieties and breeding lines at eight locations in Tennessee in 1952 to sholl' relative performance of strains at locations with and without the disease shown in Figure 12,

Highland Middle Owens' Gaby Moser1 Sloan R' T Plateau Tobacco Cocke Greene 1m enn~ssee Experiment Experiment Average Variety Jefferson Smith Experiment Experiment S' S' County County County County Station Station tatlon tahon

Pounds of tobacco 1901 Burley2 2003 1344 2592 1761 1505 2579 1733 1687 1761 Gr. 25 2088 1582 2213 1573 1588 2180 1411 1450 (Burley21) 1686 Gr. 25A 1880 1429 1771 1647 1575 2178 1593 1413 1579 1887 C;:I Gr. 26 2316 1625 2482 1659 1496 2413 1523 -::l 1747 Gr. 29 2075 1399 2258 1599 1540 2033 1466 1607 1673 Gr. 41 1944 1362 2138 1526 1396 2346 1354 1316 1811 Gr. 42 2041 1283 2323 1718 1488 2441 1614 1582 (Burley11A) Burley 1 2069 1360 2510 1614 1378 2391 1437 1345 1763 1823 Kentucky 16 2049 1546 2307 1719 1539 2175 1753 1494

Average 2052 1437 2288 1646 1501 2304 1543 1497 L.S.D.at 5-percentlevel= 128 L.S.D.at I-percentlevel= 170

1. A stalk and root di~ease was observed at the Owens and Moser farms especially on Gr. 25A. The number of diseased plants for each entry at the MOBer farm are Bhown in Table 12. Gr. 25 lines 53-406 through -410 (Table 14) showed only average performance. Gr. 25C lines 53-424 through -428 produced the highest average yield and they were best also in grade and crop indices. Of the Gr. 25 lines, 53-407 was poorest at the Station and also in a test at the Hashe farm about 10 miles northeast of the Station (Table 15). Line 53-407 also showed susceptibility to wildfire, so it was dropped from the 1954 series.

Table 14-Yield and grade quality of resistant tobacco breeding lines grown

in absence of wildfire, 19531• Family and Smoking Yield Grade2 Crop2 line or variety tobacco

Lb'/acre Percent Index Gr. 25 (Burley 2 I): 53-406 1614 79.3 .625 1012 3 53-407 161 I 79.1 .610 987 53-408 1767 75.4 .610 1076 53-409 1850 70.3 .621 1147 53-4 I0 1873 77.7 .614 1151 Average 1743 76.4 .616 1075

Gr. 258: 53-4 11 1749 82.0 .654 1146 53-412 1778 75.4 .618 1102 53-413 1864 83.6 .628 1178 53-4 I4 1674 79.5 .660 1106 53-415 1864 85.4 .650 1207 Average 1786 81.2 .642 1148

Gr. 25C: 53-424 1861 84.9 .663 1229 53-425 1808 80.4 .659 1202 53-426 1941 83.0 .647 1255 53-427 1744 79.5 .629 1097 53-428 1747 79.0 .624 1089 Average 1820 81.4 .644 1174 Gr. 30 53-433 1657 73.6 .567 936 53-434 1648 71. I .566 942 53-435 1591 66.0 .560 891 Average 1632 70.2 .564 923 Kentucky 16 1827 74.7 .595 1084 l. Four replications. 50-plant plots. 2. See footnotes 3 and 4, Table 3. 3. Discontinued as a part of Gr. 25 in 1954. 38 I I

I Tal?le 15-Yield and grade quality of resistant tobacco breeding lines grown in al?sence of wildfire, Hashe Farm, 1953'. I Family and Smaking I Yield Grade2 Crop2 line ar variety tobacca

Lb./acre Percent Index I Gr. 25 (Burley 21) : 53-406 2123 90.0 .741 1594 53-4073 2093 89.3 .725 1522 53-408 2149 77.2 .766 1659 53-409 2247 85.1 .720 1624 53-410 2164 90.5 .749 1622 Average 2155 86.4 .740 1604

Gr. 25B: 53-411 2037 90.9 .744 1516 53-412 2426 92.5 .740 1796 53-413 2385 85.0 .730 1749 53-414 2671 87.3 .751 2034 53-415 2149 91.0 .717 1588 Average 2334 89.3 .736 1737

Gr. 25C: 53-424 2404 82.4 .765 1836 53-425 2293 91.1 .770 1764 53-426 2483 90.4 .754 1878 53-427 2239 93.2 .783 1753 53-428 2192 83.0 .763 1669 Average 2322 88.0 .767 1780

Gr. 30: 53-433 2621 93.9 .798 2094 53-434 2476 92.8 .760 1883 53-435 2496 89.1 .772 1926

Average 2436 91.9 .769 1877 Burley 2 2431 89.2 .705 1720 1. Two replications, 50-plant plots. 2. See footnotes 3 and 4. Table 3. 3. Discontinued as a part of Gr. 25 in 1954.

As previously discussed under "new" disease believed caused by a strain of Phytophthora, plantings were made in 1953 at the Hashe farm to check on susceptibility of breeding lines. Because no plants of Gr. 25A or any of the large number of breeding lines planted were killed at this location in 1953, a harvest was made to determine yield and quality potential of a few of the lines in which there was special interest. Gr. 30 lines 53-433 through 39 -435 showed best average performance, but they were poorest at the Tobacco Experiment Station (Table 14). Gr. 30, first tested in extensive variety trials in 1953, has the same pedigree as Burley 21 (Figure 6) but it resulted after two more backcrosses with the variety Burley 1. During 1953, Gr. 25B and Gr. 25C, the sister lines of Gr. 25, were compared at 7 and 6 farm locations, respectively, in Tennessee (Table 16). Gr. 25 and the remaining seven entries were planted at 10 locations. Gr. 25B was superior to Gr. 25 in average yield (Table 16). The two lines were about the same in average price. According to the appraisal of leaf quality by one major company, Gr. 25B was inferior to Gr. 25. It produced only 65 percent of leaf in their best grades compared with 76 percent for Gr. 25. Another company evaluating the tobacco also preferred Gr. 25 to Gr. 25B. Consequently, Gr. 25B was dropped from variety tests in 1954. Gr. 25C performance was inferior to that of Gr. 25 in yield and crop index, but its grade quality was about the same as that of Gr. 25. Burley 2 produced the highest yield and crop index and Burley 11B was poorest. Value per acre for the entries except Burley 11B was about the same ranging from $1,111 for Burley

Table 16-Summary of cured-leaf data on tolJacco hreedirlg lines llful vane- ties at several locations in Tennessee, 1953.

Number of locations Yield Price Value and line or variety Lb./acre $/cwt.1 $/acre 7 locotions: 57.31 1162 Gr. 25 (Burley 21 ) 2006 57.23 1184 Gr. 25B 2059

6 locotions: 57.72 1202 Gr. 25 (Burley 21 ) 2075 57.88 1152 Gr. 25C 1982

10 locations: 56.70 1147 Gr. 25 (Burley 21 ) 2003 56.31 1172 Gr. 30 2059 57.27 1115 Gr. 42C 1931 57.33 1111 Burley 11A 1919 57.62 1077 Burley 11B 1848 57.01 1128 Burley 1 1960 55.60 1183 Burley 2 2113 56.19 1156 Kentucky 16 2036 Jan. 7, 1954. 1. Based on 1953 season's average prices through 40 llA to $1,183 per acre for Burley 2. Gr. 25 was intermediate with a value of $1,147 per acre.

Agronomic Results with Breeding Lines and Varieties, 1954 Progeny of individual plant selections used in making up each composite wildfire-resistant line in 1954 were evaluated for yield and quality. As shown in Table 17, significant differences were

Table 17- Yield and grade quality of resistllnt to/weco breeding lines grown ill ahsence of wildfire, 1954.

------_._-----~---_.- ..._----- Family and Smaking Yield! Grade2 Crop23 line ar variety tobocco

Lb./acre Percent Index Gr 25: 54-400 1904 67.2 .635 1207 54-401 1714 67.7 .623 1065 54-402 1769 67.5 .605 1068 54-403 2123 71.7 .638 1356 Gr 25C: 54-404 1773 81.1 .643 1146 54-405 1810 66.2 .614 1109 54-406 1969 62.3 .627 1237 54-407 1909 75.4 .665 1273 Gr 25B ( 54-408) 2007 70.6 .638 1284 Gr 30A: 54-409 2152 67.4 .658 1420 54-410 1926 72.6 .595 1145 54-411 1897 75.6 .607 1157 54-412 1867 64.7 .620 1162 54-413 1873 63.4 .606 1138 Gr. 30B: 54-415 1926 76.2 .646 1245 54-416 1814 71.9 .648 1167 54-417 1960 59.1 .583 1145 54-418 1772 78.1 .629 1117 54-419 1835 67.1 .612 1134 54-420 1809 73.3 .614 1112 Gr. 30: 54-414 1914 64.2 .608 1159 54-421 1858 73.1 .650 1208 54-422 1884 73.3 .653 1232 54-423 1877 74.0 .636 1192 Burley 1 (54-424 ) 1719 74.4 .625 1075

l. Yield. L.S.D. at 5-percent level ----- 306. 2. See footnotes ;{ and 4. Table 3.

3. Crop index L.S.D. at 5-percent level ---- 265. 41 obtained between the selections in the Gr. 25 composite. Con- sidering yield, smoking tobacco, grade index, and crop index, the average performance of Gr. 25 selections was slightly inferior to that of Gr. 25B or the Gr. 25C selections. All selections produced yields and crop indices about equal to or higher than those of the variety Burley 1.

In 1954 the performance of Gr. 25, progenitor of Burley 21, was somewhat poorer than that of other wildfire-resistant lines in the test (Table 17) of breeding lines at the Tobacco Experiment Station; however, the average performance of Burley 21 in the uniform variety trials at 12 locations was equal to or better than that of the wildfire-resistant experimental varieties Gr. 25C, Gr. 30A, and Gr. 30B (Table 18). Burley 21 was not significantly different in value per acre from the standard varieties Burley 2, Burley lIA, and Burley lIB. Gr. 31 produced the highest value per acre, being significantly better than the other entries in the test at the I-percent level of significance. Gr. 31 was not satisfactory, however, in smoking tests according to the appraisal of at least one company. In addition, it did not have resistance to wildfire or tobacco mosaic. Consequently, Gr. 31 was not considered for release as a variety even though average returns per acre were high.

Table IS-Summary of cured-leaf data on tohacco breediNg liNes (IHd varieties at twelve locations in Tennessee, 1954.

Smoking Variety Yield Gradel Crop! 2 3 tobacco Price Value

Lb'/acre Percent Index $/cwt. $/acre Burley 2 2198 70.4 .611 1412 53.22 1197 Burley 11A 2044 73.5 .622 1334 54.66 1139 Burley 11B 2009 73.0 .625 1324 54.58 1121 Gr. 25 (Burley 21 ) 2149 67.7 .605 1370 53.15 1172

Gr. 25C 2097 70.5 .623 1378 53.77 1152 Gr. 30A 2162 66.7 .589 1350 52.71 1170 Gr. 30B 2069 68.4 .597 1302 54.06 1144 Gr. 31 2404 73.2 .624 1579 54.05 1325 Gr. 32 2225 67.2 .596 1395 53.01 1205 Gr. 33 2027 69.1 .613 1312 53.86 1119

1. See footnotes 3 and 4. Table 3. 2. Based on 1954 season's average prices. 3. L.S.D. at 5-percent level-67. L.S.D. at I-percent level-88. 42 Performance of Burley 21 in Regional Variety Tests Results of variety tests in Virginia from 1953 through 1957 showed that Burley 21 was superior in yield, price, and acre-value to Burley 1, Burley 2, Va. B29, Kentucky 16, and Burley llA (Table 19). Henderson (15) has published results of burley variety tests conducted in 1958 and 1959 in Virginia. In variety tests at Waynesville and Laurel Springs, North Carolina over the 5-year period 1953-1957, Burley 21 was the best of five varieties showing an acre-value 11 percent greater than that of Kentucky 16 (Table 20). It was also highest in yield and rated second in average price. Further information on North Caro- lina variety tests conducted before 1955 are provided by Shaw (18). In tests comparing three varieties and seven experimental lines conducted at two locations in Kentucky in 1957, Bortner, Wallace and Hamilton (2) show Burley 21 produced the highest average yield, value per 100 pounds, and value per acre. In their studies, Burley 21 was intermediate with respect to the other

Tahle ]9-Co1l1parison of Burley 2] 'with five other hurley tobacco varieties at four locations in Virginia in the 5-year period ]953-1957',

Yield Price Value Variety Rank Lb./acre Rank $/cwt. Rank $/acre

1486 1 Burley 21 2402 1 61.81 1 1446 2 Burley 1 2354 2 61.42 2 1430 3 Burley 2 2334 5 61.26 4 1422 4 Va. B29 2352 3 60.45 6 1420 5 Kentucky 16 2348 4 60.47 5 1334 6 Burley 11A 2174 6 61.36 3 Blacksbu rg, Va. I. Information provided hy R. G. Henderson, Va. Agr. ~jxpt. Sta.,

Tahle 20-Co1l1parison of Burley 2] and other hurley varieties in tests at 1 two locations in North Carolina in the 5-year period 1953-]957 •

Yield Price Value Variety .- Lb.7~~--;e--R;-"-k-- --$Ic~t.---R;':;k- - - $/acre Rank

~_. ._------~-_ .._.------~.-- ~- _.------__ 1108 1 Burley 21 2307 1 48.17 2 1098 2 Burley 2 2264 2 48.63 1 1009 3 Burley 11B 2113 4 47.71 3 999 4 Burley 11A 2113 4 47.25 4 989 5 Kentucky 16 2156 3 45.87 5 1. Data pl'oviJed by Luthpl' Shaw. Mountain Research Station, Waynesville, N. C. 43 entries in concentration of potassium, nitrogen, and total alkaloid in the leaf web. In Tennessee, 9 burley varieties were grown in variety tests at four locations over a 5-year period, 1955-1959. The combined results of these tests show Burley 21 rated second in grade index and crop index. Burley 1, a high-leaf-number variety susceptible to wildfire and mosaic, was first in yield and crop index. Burley 21, however, was superior to Burley 2, Va. B29, Kentucky 16, Kentucky 35, Burley llB, Burley llA, and Kentucky 41A, which rated in that order considering crop-index values.

Cured-Leaf Characteristics of Hurley 21

When cured leaves of burley tobacco are stripped from the stalk, they are usually placed in 5 or 6 farm grades. Each farm grade in the experimental tests was assigned an appropriate U. S. Standard Grade by an experienced Federal Grader. These grades indicate the grade group, also, the quality values ranging from 1 to 5 and the color of the tobacco; e.g., grade elL means cutters of best quality and buff. A study of the amounts of tobacco produced by a variety or treatment in each grade group or color re- veals inherent characteristics of the varieties to produce tobacco with these quality characteristics. Data are provided according to grade group for Burley 21 and three other varieties (Table 21). These data were obtained by analyzing the grades assigned in a total of 28 replicated variety teRts over the ~-year period 1951- 1953. The new variety, Burley 21, produced about 2 percent more of the tobacco in flyings grade and 3 percent more in cutters grade than Kentucky 16. It produced about 6 percent less of its tobacco in leaf grades than Kentucky 16. Burley 1 was Rimilar to Burley 21 in amount of the tobacco in flying and cutter grades produced. All the varieties were about the same with reRpect to amount of tip grades. The amount of tobacco in the nondescript grade was greatest for Burley 1, which also produced the highest percentage of tobacco in the flyings grade. Both Burley 1 and Burley 21 are relatively high-leaf-number varieties, which tend to produce more thin-bodied tobacco. The four varieties varied with respect to production of tobacco in grades of different colors as shown in Table 22. Burley 21 and Burley 1 produced about 10 percent more tobacco in the buff grade 44 than Kentucky 16, but averaged less in darker grades. Tobacco leaves light in color and in flyings and cutter grades are usually in greatest demand for use in cigarette blends.

Table 21-Cmed loliacco in each g,mde group for f(J1jr hurley varieties in

Ihree seasons I.

Grade and l'olumber of Burley 21 Burley 1 Burley 2 Ky. 16 year locations2

Percent Flyings (X): 1951 10 24.3 30.4 21.8 22.1 21.0 1952 8 22.9 22.2 18.6 21.7 1953 10 23.3 24.8 20.2 Average 23.5 25.8 20.2 21.6

Cutter (C): 32.4 1951 10 35.2 32.2 33.2 1952 8 23.1 23.3 24.0 15.7 1953 10 33.4 33.7 36.5 34.3 31.2 27.4 Average 30.6 29.7

LEAF (B): 37.4 1951 10 32.2 28.3 37.8 1952 8 29.6 29.8 32.5 42.7 1953 10 29.2 26.0 26.5 28.0 Average 30.3 28.0 32.3 36.0

TIP (T): 1951 10 7.5 7.2 6.2 6.9 1952 8 12.0 11.8 14.1 12.7 1953 10 10.6 10.4 10.9 11.9 Average 10.0 9.8 10.4 10.5

NONDESCRIPT (N) : 1.0 1.2 1951 10 .8 2.0 1952 8 12.4 13.0 10.9 8.0 1953 10 3.6 5.1 6.0 4.2 Average 5.6 6.7 5.9 4.5

1. Ofridal U. S. Standard Grades as assiglwd by federal gr·ader. 2. FOllr replieations of I/IOO-sere plots PR('h at eaf'h loC'stion.

45 Table 22-Cured tobacco in different color grades for four hurley varieties in three seasons!.

Color Humber Ky. 16 grade and lacatians2 Burley 21 Burley 1 Burley 2 year tested

Percent Buff or straw color (L): 29.4 1951 10 41.3 40.4 34.7 5.6 1952 8 14.7 24.3 10.5 26.8 1953 10 36.6 37.0 23.7 20.6 Average 30.9 33.9 23.0

Tan (F): 1951 10 45.6 46.2 50.2 1952 8 58.3 53.1 60.3 1953 10 43.2 55.1 52.1 Average 49.0 51.5 54.2

Reddish tan (FR): 10.4 1951 10 9.4 99.0 12.1 7.4 6.9 1952 8 7.4 5.9 1953 10 11.1 8.4 10.3 10.5 Average 9.3 7.8 9.9 9.3

Red (R): 5.1 1951 10 2.4 4.5 5.2 9.0 1952 8 6.4 8.5 10.1 4.8 1953 10 5.3 3.7 4.6 Average 4.7 5.6 6.6 6.3

Dark red (D): 1951 10 1.2 0.5 0.8 2.4 1952 8 o o o o 1953 10 o 0.2 0.5 0.2 .4 .4 Average .2 .8

Green (G): 1.0 1951 10 0.1 0.4 2.5 1952 8 13.2 12.3 18.9 18.2 1953 10 3.9 3.9 5.9 5.6 Average 5.7 5.5 8.6 8.8

1. Official u.s. Standard grades as assigned by federal grader. 2. Four replications, 1/100-acre plot at each locatirm.

46 Nicotine Content of Burley 21 and Other Varieties, 1951-1959 Data are provided (Table 23) showing the average nicotine content of Burley 21, Burley 1, Burley 2, and Kentucky 16 at three locations during a 3-year period. Three stalk positions were sampled. These are designated flyings, cutter, and leaf grades, which represent farm grades 2, 3, and 4, respectively, in these studies. The differences in nicotine content between the varieties were very small. Average nicotine content of the three grades ranged from 2.86 to 4.40 for flyings and leaf grades, respectively. About the same degree of variation was observed during the 3-year period which, considering all varieties and grades, averaged 4.53 percent in 1952, a dry season, and 3.16 in 1951, a season with

Tallie 23-N icotine content of four burlcy tobacco varieties in the 3-ycar

1 period 1951-1953 •

Nicotine content of indicated grade2 Variety and ~~~~~~~- year Flyings Cutter Leaf Average

Percent Burley 1: 1951 2.37 3.46 3.92 3.25 1952 3.57 4.68 5.03 4.43 1953 2.52 3.95 4.76 3.74 Average 2.82 4.03 4.57 3.81

Kentucky 16: 1951 2.34 3.35 3.49 3.06 1952 3.82 4.73 5.04 4.53 1953 2.57 3.73 3.72 3.34 Average 2.91 3.94 4.08 3.64

Burley 21: 1951 2.30 3.56 3.93 3.26 1952 3.77 4.72 5.06 4.52 1953 2.40 3.57 4.57 3.51 Average 2.82 3.95 4.52 3.76

Burley 2: 1951 2.27 3.25 3.67 3.06 1952 3.87 4.96 5.11 4.65 1953 2.46 3.42 4.50 3.46 Average 2.87 3.88 4.43 3.73 1. Results of analysis conducted by D. R. Bowman, Plant Physiologist, Crops Research Division, Agricultural Research Service, U. S. Department of Agriculture, Knoxville, Tennessee. 2. Three locations and two replications at each location in each year. 47 more normal rainfall and with higher yields of leaf. These varieties show inherent variation also with respect to the amount of tobacco flyings, cutter, and leaf (Table 21). This affects, to some extent, the stalk position represented by the farm grade and there- fore the nicotine content. Greatest difference in nicotine content for the varieties seems to be in the leaf grades in 1951 and 1958. In these years, the leaf grade of Kentucky 16 was appreciably lower in nicotine than the other varieties. The varieties showed, however, almost identical values at this and other stalk positions in 1952. Although Burley 21 was similar to other varieties in nicotine content, as shown in Table 28, other analytical data indicated that the nornicotine content of Burley 21 was elevated and the nicotine content was lower than that of some other burley varieties. Up to 10 percent of the total alkaloid was nornicotine in a few samples, whereas 5 percent or less nornicotine is considered normal. Further study and analysis of leaf from individual plants revealed that only a small percentage of the plants had elevated values. A few plants produced more nornicotine than nicotine. In 1957 all abnormally high nornicotine plants were removed from the foundation seed planting of Burley 21. The analyses by paper chromatography of the Burley 21 samples from Greeneville, Tennessee, were made by R. N. Jeffrey and T. Sorokin in U. S. Department of Agriculture laboratories at Beltsville, Md. Several hundred plants were tested individually and relatively high nornicotine plants were removed before bulking the seed and supplying it to certified seed growers. In one year, the level of nornicotine for Burley 21 was lowered to almost the desired level. A similar procedure of indexing individual plants and removing those with elevated nornicotine content was followed also during 1958 and 1959. Only relatively small reduction in the level of the alkaloid was possible after the 1957 testing. Actually, the analysis of the 1959 planting provided satisfactory evidence that Burley 21 waf now normal with respect to alkaloid production. Although many favorable reports on the smoking quality of Burley 21 were received from manufacturers, other breeding lines and varieties with high nornicotine were unsatisfactory in smoking quality (17). The possibility of further quality improvement of Burley 21 seemed to justify the chemical testing of individual foundation seed plants and removal of those with highest nornicotine content. The benefits of this research were passed along each year to the tobacco growers by providing the seed growers with the new foundation seed stocks. 48 DISCUSSION

The development of Burley 21, the first wildfire-resistant tobacco variety of any type, required more than 20 years of plant- breeding research, beginning in 1938, when the successful interspecific hybrid between N. tabacum and N. longiflora was made by Clayton (4). Although Burley 21 was released for planting in 1955, further selection was desirable in 1957, 1958, and 1959 to remove individual plants with too high nornicotine content. Improvements were effected especially the first year. Analytical data provided by tobacco companies on the alkaloid content of leaf samples from the 1958 variety tests showed that Burley 21 had a level of nornicotine like that of other commonly grown burley varieties. Since 1955, when Burley 21 was released, it has become a very popular variety with growers throughout the burley area. More than 150,000 acres, or more than 50 percent of the burley acreage, was planted to Burley 21 in 1959 and 1960, according to reports of seed sales and from extension personnel. The variety provides not only excellent control of wildfire and tobacco mosaic but also high yields of grades desired for cigarette blends. It ''lo produces vigorous early plants and has good stand up characteristics that make it easier to cultivate and harvest without leaf breakage.

In a few fields, wildfire on Burley 21 has been observed but the amount of leaf injury was less than on susceptible varieties. Presence of wildfire on Burley 21 may have resulted from either the development of new strains of bacteria able to attack this or other similarly resistant varieties or from the appearance of some plants which have lost the genes for resistance. Observations over the past 5 years with Burley 21 planted on much of the burley acreage seems to indicate that the resistance is adequate and continued good disease control may be expected. Growers do not need to use chemical measures to control wildfire in plant beds

"l when this variety is seeded. Burley 21, like other burley varieties, is susceptible to frogeye (Cercospora nicotianae Ell. & Ev.), a fungus disease which is frequently confused with wildfire because of the similarity in their symptoms. The variety has been used in many crosses with varieties of other tobacco types as a source of wildfire resistance and also in crosses to combine resistance to wildfire and tobacco mosaic with resistance to black shank and fusarium wilt. Breeding lines 49 with combined resistance to all of these diseases have been in the cooperative breeding program at the Tobacco Experiment Station since 1952. At least 500,000 seedlings were evaluated for wildfire resistance in plant beds at the Tobacco Experiment Station in the development of Burley 21. About 75,000 of the most vigorous surviving plants were transplanted to field plots for further testing of resistance to wildfire, to test for resistance to tobacco mosaic, and to make a preliminary evaluation of agronomic characteristics. Each year parallel seedings and plantings were made in beds and fields where plants were not inoculated with wildfire in order to complete the evaluation of agronomic characteristics. In each year since 1951, cured leaf samples of Burley 21 and of standard varieties from many variety tests have been displayed on ware- house floors so that leaf experts of manufacturing companies could appraise the physical characteristics of cured leaf and the companies could obtain samples for chemical determinations. At least three major tobacco companies took part in the evaluations. Company appraisal of quality resulted in the rejection of several experimental lines, such as Gr. 26 and Gr. 30. These were high- yielding lines which otherwise had good production performance in variety tests. In addition to breeders and manufacturing companies, extension personnel, Federal tobacco graders, variety test cooperators, and many others were involved in different phases of the extensive breeding program. It seems impractical to record here all the details of the tests performed in connection with the variety development. How- ever, the background information presented does call attention to the more significant efforts, and shows the magnitude of the research program required to produce Burley 21 or any crop variety with resistance to disease from a related species. Judging by its popularity with growers, Burley 21 has many characteristics which make it attractive.

LITERATURE CITED 1. Anderson, P. J. Susceptibility of Nicotiana species. Phytopath. 15:77-84. 1925. 2. Bortner, C.E., Wallace, A.M. and Hamilton, J. L. Differences in potassium, nitrogen and total alkaloid concentration of ten burley tobacco varieties. Tobacco 151:20-24. (Tobacco Science 4:151-155) 1960. 3. Braun, Armin C. A comparative study of Bacterium tabacum Wolf & Foster and Bacterium angulatum Fromme & Murray. Phytopath. 27: 283-304. 1937. 50 4. Clayton, E. E. A wildfire resistant tobacco. Jour. Heredity 38: 35-40. 1947. 5. Clayton, E. E., IIegg'estad, H. E., Grosso, J. G., Bowman, D. R. and Scbneidel', E. O. Breeding behavior and growth responses resulting from the transfer of wildfire res If,tance from Nicotiana !ongiflora to N. tabacum. (Abst.) Phytopath. 41: 7. 1}J51. G. Garber, E. D. and Heggestad, H. E. Observations on the pathogenicity of biochemical mutants of Pseudomonas tabaci. Phytopath. 48 :535-537. 1%8. 7. Graham, T. \'Y. and Heggestad, H. E. Growth response and root decay dcvelopment in certain tobacco val'ieties and breeding lines infected with !'Oot-lesion nematodes. Tob. Sci. ;~:172-178. 195D. 8. IIeggestad, H. E. Varietal vm'iation and inheritance studies on natural watel' soaking in tobacco. Phytopath. 35 :754-770. Hl45. D. l-Ieggestad, H. E. Burley tobacco disease situation in Tennessee-1948. PI. Dis. Rpt!'. ;~2:507-508. 1!J4~L 10. Heggestad, H. E. am] Clayton, E. E. Bul'!ey 1, a new black root rot resistant tobacco. Tenn. Expt. Sta. Circ. lOG. 1951. 11. lIeggestad, H. E. and Clayton, E. E. Development of burley varieties of tobacco resistant to black shank, fusarium wilt, wildfil'e, tobacco mosaic, and black root rot. (Abst.) Phytopath. 15:4(j:L 1!J55. 12. Heggesta(], H. E. and Neas, ]VI. O. Blfl'!ey 2, a new improved variety of tobacco. Tenn. Expt. Sta. Cil'C. 110. 1!J5:L 1:). Heggestad, H. E., Clayton, E. E. and Felts, J. Hugh. Wildfire resistant tobacco. Tenn. Farm & Home Sci. Prog. Rpt. No. 11. July-Sept. 1D54. 14. Heggestad, H. E. and Neas, ]VI. O. The disease resistant varieties Burley llA and llB and observations on tobacco black shank in Tennessee. Tenn. Expt. Sta. Bul. 261 :1-25. 1!J57. 15. Henderson, R. G. Performance of tobacco varieties and breeding lines tested in Virginia in Hl58 and 1!J59. Va. Agr. Expt. Sta. }{esearch Report 37:5D p. 1%0. 1G. Johnson, James, Slagg, C. M. and Murwin, II. T. Host plants of Bac- terium tabacum. Phytopath. 14:175-180. 1!J24. 17. Moseley, J. M. Observations on the smoke taste of certain burley breeding lines. Paper presented at Burley Workers' Conference, Abingdon, Va. Aug. 1!J5G. 18. Shaw, Luther. Measured crop performance burley tobacco. N. C. State College Res. Rpt. 1G. 1~l55.

1!J. Valleau, W. D. and Diachun, S. Tobacco diseases in KentuckY 111 1948. PI. Dis. Rptr. 32:505-507. 1948. 20. Valleau, W. D. and Troutman, J. 1.. A review of the wildfire problem in Kentucky tobacco. Ky. Expt. Sta. Bul. 570:1-8. 1D51.

21. Wolf, F. A. and Foster, A. C. Tobacco wildfire. J. Agr. Res. 12: 449-458. 1918. 4M-3-61 51 OF TENNl=c;c;l~J.' EXPERIMENT STATION KNOXVILLE, TENNESSEE

Committee of Trustees

D. HOLT, President M. YORK, Chainnan LAUGHLIN, WASSELL RANDOLPH of Agriculture

OFFICERS

K. L. HERTEL, Physics J. O. ANDES, PlaDt Pathology

MAIN STATION J. N. ODOM, Farm Superintendent, Knox· ville Di· SUBSTATIONS B. P. HAZLEWOOD,Supt., West Tennessee Experiment Station, Jackson T. J. WHATLEY, Program Director, Ames Plantation, Grand Junction M. SAFLEY, Supt., Highland Rim Experiment Station, Springfield E. J. CHA:PMAN,Supt., Middle Tennessee Experiment Station, Spring Hill R. OWEN, Supt., Dairy Experiment Station, Lewisburg J. A. ODOM, Supt., Plateau Experiment Station, Crossville KRING, In Charge, Bryn Mawr Wartburg Tobacco Experiment