AN ABSTRACT OF THE THESIS OF
Jean Ann Gleichsner for the degree of Doctor of
Philosophy inCrop Sciencepresented on June 27, 1988 .
Title: Biology of Bromus rigidus: Interference in Winter Wheat, Seed Longevity in the Soil, and Vernalization Requirements for Flowering
Abstract approved:!Redacted for Privacy / 1 Arnold P. Appleby
Greenhouse and field studies were conducted to examine various biological aspects of ripgut brome (Bromus rigidus Roth). A field experiment was conducted to measure the grain yield of winter wheat (Triticum aestivum L. Stephens') at various ripgut brome and wheat plant densities. Wheat yield decreased as ripgut brome density increased at all wheat seeding rates (56, 112, 168, and 224 kg/ha). Grain yield was unaffected by wheat seeding rate in the absence of brome. Increasing seeding rates above 112 kg/ha to reduce wheat yield loss caused by ripgut brome is ineffective.
In the field, both surface-sown and buried (1 to 30 cm) ripgut brome seed were depleted within 15 months.
Persistence of surface-sown seed declined slowly during the first year, falling from 83 to 62 to 23% after 1, 9, and 12 months, respectively. Seed covered by soil, however, germinated more rapidly, with less than 10% of the initial population ungerminated after 1 month at all depths. The mode of seed disappearance was closely related to whether or not seed were covered with soil. Seed loss at depths of 1 to 30 cm was primarily due to germination in situ, with little effect from viability loss or enforced or induced dormancy. In contrast, the persistence of surface-sown seed was due primarily to induced dormancy for up to 12months, with nonviability loss and enforced dormancy becoming important thereafter. Ripgut brome has a quantitative requirement for vernalization in order to flower. In greenhouse studies, cold treatment (5 + 2 C) of 2, 4, or 6 weeks shortened the vegetative period, but longer exposure did not further decrease the time required to flower. Plants vernalized as imbibed seed for 8 weeks took 17 days to flower following transfer from cold treatment to the greenhouse. Unvernalized controls flowered 53 days after planting in the greenhouse. Highest total seed dry weight and total shoot dry matter was produced by unvernalized plants; lengthening periods of vernalization from 2 to 8 weeks decreased both measurements. In field studies, ripgut brome plants established in the fall flowered sooner after resumption of growth in the spring than those planted in the spring.
Plants seeded after April failed to flower until the following spring. Biology of Bromus rigidus: Interference in Winter Wheat, Seed Longevity in the Soil, and Vernalization Requirements for Flowering
by
Jean Ann Gleichsner
A THESIS
submitted to
Oregon State University
in partial fulfillment of the requirements for the degree of
Doctor of Philosophy
Completed June 27, 1988
Commencement June 1989 APPROVED: Redacted for Privacy Professor of Crop Science in /clerge of jor Redacted for Privacy Head of Department, Crop Science
Redacted for Privacy Dean of Graduate School
Date thesis presented June 27, 1988
Typed by Jean A. Gleichsner ACKNOWLEDGEMENTS
I consider myself extremely fortunate to have made some
very good friends while studying at Oregon State University.
Two friends that deserve special mention are Bernal Valverde
and Dan Peek. This thesis would not have been possible
without their help and encouragement. Despite many trying
moments, they refused to give up on me and more importantly
made sure I didn't give up. Their tactics weren't always
pleasant, but they were sure effective. I also would like
to extend gratitude to their families for providing
friendship and some very memorable moments.
I am very grateful to Bob Spinney and Bill Brewster for
their help in getting my field work done. Even with their
demanding workload, they always made time to help me.Many
thanks to Jeannette Emry for her secretarial assistance.
I thank the members of my graduate committee, Dr.
Arnold Appleby, Prof. Larry Burrill, Dr. Mark Wilson, Dr. Kenton Chambers, and Dr. Tom Bedell for their time and
guidance. I also am grateful to Dr. Roger Fendall for the
opportunity to teach the Crop Science Laboratory.Teaching and interacting with students were some of the brightest moments at Oregon State.
Special thanks to my parents and family. Although they didn't always understand what I was doing, they were always
there to provide love and support. Thank you Mom for encouraging my dream of teaching. Looks like I finally made it come true. Jane, its difficult to express my appreciation for the financial support you gave me throughout my college years. You really don't know how important it was to me. Bonnie, thank you for keeping me up with the news on the home front. Even though I couldn't be there, you made sure I knew what was going on.
Finally, a sincere thank you to Caren Augustine.
Despite the distance and lack of contact, you have remained a very good and dear friend to me. TABLE OF CONTENTS
INTRODUCTION 1
CHAPTER 1. Ripgut brome (Bromus rigidus) interference in winter wheat: Plant density effects. 7
Abstract 7
Introduction 8
Materials and Methods 9
Results and Discussion 11
Literature Cited 21
CHAPTER 2. Effect of depth and duration of seed burial on ripgut brome (Bromus rigidus). 22
Abstract 22
Introduction 23
Materials and Methods 25
Results and Discussion 29
Literature Cited 40
CHAPTER 3. Vernalization requirements for flowering of ripgut brome (Bromus rigidus). 42
Abstract 42
Introduction 43
Materials and Methods 45
Results and Discussion 50
Literature Cited 59
GENERAL DISCUSSION 61
BIBLIOGRAPHY 66
APPENDIX 69 LIST OF FIGURES
Figure Page
1.1 Effect of brome density on wheat grain yield 18
1.2 Effect of brome density on total wheat shoot 19 number per unit area.
1.3 Effect of brome density on wheat above-ground 20 biomass.
2.1 Monthly precipitation and mean monthly soil 38 temperature at a depth of 10 cm from November 1985 to October 1987 recorded at Hyslop Research Farm near Corvallis, Oregon.
2.2 Model used to partition weed seed recovered 39 from soil into components of persistence (Pex Pend) and depletion (Dg + Dn).
3.1 Effect of date of planting in the field on the 58 emergence and flowering of ripgut brome. LIST OF TABLES
Table Page
1.1. Comparison of yield regression lines for 15 homogeneity of intercepts and slopes.
1.2. Average winter wheat grain yields attained 16 with varied winter wheat seeding rates and ripgut brome densities.
1.3. Effect of brome density and wheat seeding 17 rate on total brome shoot number per unit area.
2.1. Effect of depth and duration of burial on 33 persistence (Pex Pend) of ripgut brome seed.
2.2. Effect of depth and duration of burial on 34 in situ germination (Dg) of ripgut brOme seed.
2.3. Effect of depth and duration of burial on 35 nonviability loss (Dn) of ripgut brome seed.
2.4. Effect of depth and duration of burial on 36 enforced dormancy (Pex) of ripgut brome seed.
2.5. Effect of depth and duration of burial on 37 induced dormancy (Pend)of ripgut brome seed.
3.1. Mean daily maximum and minimum monthly air 54 temperature recorded at Hyslop Research Farm near Corvallis, Oregon.
3.2 Effect of vernalization duration at 5 C on days 55 to flowering, culms per plant, plant height, total seed dry weight, total shoot dry weight, and the ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhouse.
3.3 Effect of outdoor cold treatment on days to 56 flowering, culms per plant, total seed dry weight, total shoot dry weight, and the ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhouse. LIST OF APPENDIX TABLES
Table Page
1. Effect of ripgut brome density on winter wheat 69 grain yield.
2. Analysis of variance table for effect of ripgut 70 brome density on winter wheat grain yield.
3. Effect of winter wheat seeding rate and ripgut 71 brome density on total number of winter wheat shoots per unit area.
4. Effect of ripgut brome density on total number 72 of ripgut brome shoots per unit area.
5. Effect of winter wheat seeding rateand ripgut 73 brome density on total winter wheatabove-ground biomass.
6. Effect of winter wheat seeding rateand ripgut 74 brome density on total ripgut bromeabove-ground biomass.
7. Effect of vernalization duration at 5 C on days 75 to flowering, culms per plant, total shoot dry weight, total seed dry weight, and ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhouse. Year 1.
8. Effect of vernalization duration at 5 C on days 78 to flowering, culms per plant, total shoot dry weight, total seed dry weight, and ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhouse. Year 2.
9. Analysis of variance table for effect of vernal- 81 ization duration at 5 C on days to flowering of ripgut brome after transfer to the greenhouse.
10. Analysis of variance table for effect of vernal- 81 ization duration at 5 C on culms per plant of ripgut brome after transfer to the greenhouse.
11. Analysis of variance table for effect of vernal- 82 ization duration at 5 C on total shoot dry weight of ripgut brome after transfer to the greenhouse.
12. Analysis of variance table for effect of vernal- 82 ization duration at 5 C on total seed dry weight of ripgut brome after transfer to the greenhouse. 13. Analysis of variance table for effect of vernal- 83 ization duration at 5 C on ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhouse.
14. Effect of outdoor cold treatment on days to 84 flowering, culms per plant, total shoot dry weight, total seed dry weight, and ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhouse. Year 1.
15. Effect of outdoor cold treatment on days to 88 flowering, culms per plant, total shoot dry weight, total seed dry weight, and ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhouse. Year 2.
16. Analysis of variance table for effect of outdoor 92 cold treatment on days to flowering of ripgut brome after transfer to the greenhouse.
17. Analysis of variance table for effect of outdoor 92 cold treatment on culms per plant of ripgut brome after transfer to the greenhouse.
18. Analysis of variance table for effect of outdoor 93 cold treatment on total shoot dry weight of ripgut brome after transfer to the greenhouse.
19. Analysis of variance table for effect of outdoor 93 cold treatment on total seed dry weight of ripgut brome after transfer to the greenhouse.
20. Analysis of variance table for effect of outdoor 94 cold treatment on ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhouse. BIOLOGY OF BROMUS RIGIDUS: INTERFERENCE IN WINTER WHEAT, SEED LONGEVITY IN THE SOIL, AND VERNALIZATION REQUIREMENTS FOR FLOWERING
INTRODUCTION
Ripgut brome (Bromus rigidus Roth), a winter annual grass, is native to Europe and northern Africa butis now quite common along the Pacific Coast of North America from
British Columbia to Mexico (Hawkes et al., 1985). In
Oregon, this plant is much more common west of the Cascade
Mountains. Generally considered a weed of waste areas, roadsides and railroads, ripgut brome also invades rangeland and cultivated crops (Hitchcock, 1950). In the seedling stage, ripgut brome has tubular sheaths, but in age may split to the base. Blades and sheaths are covered with soft hairs, easily seen with the naked eye. The mature plant is usually 1 to 3 feet tall. The inflorescence is open, nodding, and 3 to 8 inches long with few flowers. Spikelets contain five to eight flowers, each of which are 1 1/2 to 2 inches long and with awns as much as 2 1/4 inches long (Hawkes et al., 1985). Ripgut brome has little forage value except for a short period before maturity; the long stiff awns on the mature seed can cause mechanical injury to the nose and eyes of grazing animals (Fischer et al., 1983). In cereal fields, ripgut brome causes yield losses as well as grain contamination. 2
Ripgut brome (B. rigidus) is often confused with great
brome (Bromus diandrus Roth), which also is sometimes called
ripgut brome. The two species, however, can be distinguished from each other by the following
characteristics: a) Length of the panicle branch for B.
diandrus is much longer than its spikelet (up to 12 cm) in comparison to B. rigidus in which length of panicle branch
almost equals spikelet length. b) B. rigidus has a pubescent abaxial leaf surface, whereas B. diandrus does
not. c) Pubescence is present at the culm nodes of B.
rigidus but not in B. diandrus. These characteristics, however, often are sufficiently variable that identifying
the species on the basis of morphology is difficult.
Fortunately, chromosome number differs between B. rigidus, and B. diandrus with 42 and 56 chromosomes, respectively
(Moore, 1973), and accurate distinction between themcan be made with this method.
Studies involving ripgut brome have been primarily conducted on the rangelands of the Western United States,
particularly in California. Originally comprised of
perennial grasses, California grasslands have shiftedto introduced European annual species (Munz and Keck, 1959).
Although composition of the annual type varies greatly,one of the predominant grasses is ripgut brome (Biswell, 1956).
Response of this species varied with fertility and soil moisture regime (Hull and Muller, 1976). Fertilization increased the mean dry weight of ripgut brome and increased 3 or did not change shoot number per unit area. This resulted in increased productivity with fertilization. The proportion that ripgut brome contributed to the total yield of the rangeland increased with fertilization.
Thus, there was a shift in the importance of ripgut brome species to the total yield.
Vegetative response to increased moisture supply was similar, although not as dramatic as that of fertilization.
Hull and Muller (1976) suggested that range management policies that increase fertility or moisture might lead to an alteration of the composition of the annual grasslands.
Annual grass species exhibit yearly cycles of growth rates and phenologies that correspond closely to weather patterns (Hufstader, 1976). Maximum growth of ripgut brome occurred during winter and early spring and was significantly correlated with rainfall from November to June
(Hufstader, 1978). Species characteristics are important factors in plant development following germination, whereas, rainfall is critical to germination and growth rates.
Young et al. (1973) investigated the effect of constant and alternating temperatures on the germination of ripgut brome in an annual-type rangeland community. Temperature combinations were alternated through a 16 hr (night) and 8 hr (day). All combinations were used for -4, -2, 0, 2, 5, and 5-degree increments through 40 C. A night temperature of at least 0 C was required for germination with any day temperature of 10 to 30 C, and a night temperature of 2 C 4
was required for germination at 5 C in the day. Highest germination occurred at day temperatures of 15 or 20 C with corresponding night temperatures of 5 or 2 C, respectively. Ripgut brome seed were collected in mid-June from
central and northern California grasslands and tested for
variability in seed germination behavior (Jain, 1982). Six weeks after harvest, a high level of seed dormancy (63.8 +
10.4%) existed in ripgut brome, but this dropped
significantly 12 weeks after harvest (12.0 + 6.6%). Little or no research is available about ripgut brome
in cultivated crops, including winter wheat (Triticum
aestivum L.). Undoubtedly, this is a reflection of its
recent recognition as a problem in wheat fields. Weeds such as wild oat (Avena fatua L.) and Italian ryegrass (Lolium multiflorum Lam.) have predominated as the problem weeds in winter wheat west of the Cascades. With the advent of the herbicide diclofop, (+)-2-(4-(2,4-dichlorophenoxy)phenoxy] propanoic acid, these weeds have been adequately controlled.
Unfortunately, a crop is never able to fully exploit all available resources; thus niches are left. These niches are soon filled with weeds either new to the area or less competitive than previous weed species. Ripgut brome may be such a weed.
Sometimes it is too easy to point to a herbicide and say this is what caused the species shift in a crop field.
More often than not it is a combination of events that have led to such a change. For example, the need for resource 5 conservation has led to less tillage and an increase in residue left on the soil surface. Less tillage allows some weeds to produce seed, whereas before they were prevented from reproducing. Increased residue lowers the temperature at the soil surface which may lead to germination of some weed seeds previously ill-favored by exposure on the bare soil. Speculation on the development of a new weed problem is unlimited, especially when field histories do not exit or are, at best, merely a record of herbicideapplication. Selective herbicides for ripgut control in wheat have been inconsistent, too expensive, or not expected to be registered in the United States. Thus, alternative control practices are needed. A better understanding of the biology of ripgut brome may suggest more effective and economical control strategies. Research reported in Chapter 1 was undertaken to measure wheat grain yields at various wheat and ripgut brome densities. Increased seeding rates of crops have proven effective in reducing both weed growth and weed-caused crop loss (Godel, 1935, Thurston, 1962). Research in Chapter 2 determined the effect of depth and duration of seed burial on ripgut brome seed persistence in soil. Research in Chapter 3 determined the vernalization requirements for flowering of ripgut brome.
Each chapter was written as a complete and self- contained manuscript. Detailed data and statistical 6 analysis tables are in the Appendix. 7
Chapter 1. Ripgut Brome (Bromus rigidus) Interference in Winter Wheat: Plant Density Effects
ABSTRACT
A field experiment was conducted to measure the grain yield of winter wheat (Triticum aestivum L. Stephens') at various ripgut brome (Bromus rigidus Roth) and wheat plant densities. Wheat yield decreased as ripgut brome density increased at all wheat seeding rates (56, 112, 168, and 224 kg/ha). Reduction in grain yield was most pronounced at the lowest wheat seeding rate. Grain yield was unaffected by wheat seeding rate in the absence of brome. Increasing seeding rates above 112 kg/ha to reduce wheat yield loss caused by ripgut brome is ineffective. Increasing ripgut brome density decreased wheat shoots per unit area and above-ground biomass. Brome shoot number per unit area increased as brome density increased. 8
INTRODUCTION
Ripgut brome is a troublesome weed in rangeland, noncropland, and, occasionally, cultivated crops. This winter-annual grass is a native of Europe and northern
Africa but is now quite common along the Pacific Coast of North America from British Columbia to Mexico (4, 5). Ripgut brome reduces crop growth through competition, causes mechanical injury to the nose and eyes of grazing livestock, and contaminates cereal grain (2).
Little research has been conducted on ripgut brome, other than requirements for germination (8, 12) and management practices for its use in annual grasslands (6,
7). In winter wheat, control programs have focused on
finding a herbicide to selectively control ripgut brome. At present, attempts have been unsuccessfull. Thus, other control measures must be examined.
One of the ways to reduce the competitive effects of weeds is to increase crop density. Increased cereal stand or seeding rate has been shown to decrease both weed growth and weed-caused crop loss (3, 11). The objective of this study was to: a) measure wheat grain yields at various wheat and ripgut brome densities, and b) establish economic thresholds and estimate maximum yield loss potential.
'B. D. Brewster, Dep. Crop Sci., Oregon State Univ., Corvallis, OR. Personal communication. 9
MATERIALS AND METHODS
Mature ripgut brome seed were hand-harvested from a
field with a history of winter wheat production at the
Oregon State University Botany Farm near Corvallis, Oregon,
in July 1985. Seed were mechanically cleaned, deawned for easier handling, and stored at room temperature until used.
Hereafter, the term 'seed' refers to a completegrass floret including the palea and lemma.
Because of similarities in morphology, ripgut brome (B. rigidus Roth; 2n=42) is often confused with great brome (B.
diandrus Roth; 2n=56), which also is sometimes calledripgut brome (9). Chromosome counts conducted by the Oregon State University Seed Laboratory, Corvallis, Oregon, verified that the species used in this study was B. rigidus.
A field experiment was established on October 14, 1986, at Hyslop Research Farm near Corvallis, Oregon. Soil type was a Woodburn silt loam (fine-silty, mixed, mesic Aquultic
Argixeroll). Fertilizer was applied preplant incorporated at 336 kg/ha (16-20-0) and an additional 448 kg N/haas urea was added in a spring topdressing. Diuron [N'-(3,4- dichloropheny1)-N,N-dimethylurea)] at 0.8 kg ai/hawas applied 3 weeks after planting, primarilyto control annual bluegrass (Poa annua L.). This rate caused no visible injury to the brome in the 1986-1987season.
Experimental design was a split-plot replicated infive randomized blocks. Wheat seeding rates (56, 112, 168, and 10
224 kg/ha) were assigned to the main plots and ripgut brome levels (0, 100, 400, 800, and 1450 seeds/m2) to subplots within each main plot. Each main plot was 12.2 m wide by 7.3 m long and subplots were 2.4 m wide by 7.3 m long with rows spaced 0.18 m apart. Ripgut brome plots were established by broadcasting weighed amounts of seed over the area and then planting 'Stephens' winter wheat with a grain drill. The drill mixed some of the brome seed into the surface layer of soil, similar to the situation with a natural brome infestation. Because ripgut brome matures earlier than winter wheat, above-ground biomass (ripgut brome and winter wheat) was determined in mid-June from two 0.1-m2 quadrats in each subplot. Samples were dried at 60 C for 48 h and weighed, and shoots per unit area of both species were counted.
Shoots per plant could not be determined because of intermingling of the large number of plants. At maturity
(mid-July), wheat grain was harvested from each subplot with a small-plot combine. Regression analysis was used to quantify the effects of increasing plant density on wheat grain yield, plant above-ground biomass, and shoot number. Analysis of variance was computed for average winter wheat grain yields and differences between means were compared using Fisher's protected Least Significant Difference (LSD)
Test at the 0.05 level of significance. 11
RESULTS AND DISCUSSION
In order to decide whether or not weed control is economically beneficial, a basic requirement is the knowledge of the extent by which a given weed infestation is likely to reduce crop yield if uncontrolled. Wheat grain yield decreased at all wheat seeding rates as ripgut brome density increased. Regression analyses revealed a linear relationship between ripgut brome density and wheat grain yield at each wheat seeding rate (Figure 1.1). Wheat yields were reduced much more strongly in response to brome pressure at the low crop density (56 kg/ha) than at higher crop densities (112 kg/ha and above). Regression equations predicted a decrease in wheat grain yield from 2.2 kg/ha for each weed plant/m2 at 168 or 224 kg/ha wheat seeding rate to
4.0 kg/ha at 56 kg/ha wheat seeding rate. Coefficients of determination (r2) indicated that 83 to 99% of the variability in wheat grain yield could be attributed to weed density. A comparison of regression equations (Table 1.1) showed that increasing ripgut brome densities caused similar reductions in wheat yield at the higher wheat seeding rates
(112 kg/ha and above), but not at 56 kg/ha. For example, at
200 weed plants/m2, grain yield was reduced 11% at 56 kg/ha wheat seeding rate and only 5 to 6% at higher wheat seeding rates. At the highest brome density (approximately 1170 plants/m2), grain yield at 56 kg/ha was reduced by 61%, 12 whereas reductions in yield at higher wheat seeding rates ranged from 31 to 37%. Unfortunately, maximum crop yield loss can not be estimated because weed densities were not high enough.
Under weed-free conditions or low ripgut brome densities (95 plants/m2), wheat yields were similar at all seeding rates (Table 1.2). At all brome densities above 95 plants/m2, wheat grain yield significantlyincreased when wheat seeding rate was doubled from 56 kg/ha to 112 kg/ha.
Further seeding rate increases, however, did not result in significant increases in grain yield. Ripgut brome levels of 333 plants/m2 or higher significantly reduced yields at
56 kg/ha wheat seeding rate, whereas at 112 kg/ha wheat seeding rate brome levels had to be higher than 333 plants/m2 before yieldwas significantly lower than under weed-free conditions (Table 1.2). Planting wheat at 112 kg/ha would be expected to give similar grain yields to that of 168 or 224 kg/ha for any initial brome density within the range of densities used in this experiment.
As ripgut brome densities increased per unit area, wheat shoot number per unit area declined, regardless of seeding rate (Figure 1.2). The decrease in wheat shoots per unit area undoubtedly contributed to lower wheat yields.
The effect of increasing brome densitieson wheat shoots per unit area was most severe at the lowest wheat seedingrate. The regression equations predicted a decrease in wheat shoots from 0.12 shoots/m2 for each weed plant/m2at 224 13
kg/ha wheat seeding rate to 0.23 shoots/m2 at 56 kg/ha wheat
seeding rate. In field studies, wild oat (1) and Lolium rigidum (10) also lowered wheat yield by reducing wheat
shoot number.
Increasing ripgut brome densities also reduced above- ground wheat biomass (Figure 1.3), but relative biomass
reductions were similar at all wheat seeding rates.
At all wheat seeding rates, increasing brome densities
increased the number of brome shoots per unit area (Table
1.3). Even though the density at the highest brome level was almost double of the next lowest density (1170 vs 643
plants/m2), brome shoot numberswere similar. An initial brome density of 1170 plants/m2 probably led to increased
intraspecific competition among brome plants, as well as less vigorous plants that were more susceptible to winter
injury and death. This mortality resulted in reduced brome shoot production.
In summary, increasing densities of ripgut brome reduced wheat grain yields regardless of wheat seeding rates. The effects, however, were more pronounced at the lowest seeding rate (56 kg/ha). This seeding rate is below the rate commonly used by growers in the Willamette Valley.
Under weed-free conditions, a wheat seeding rate of 56 kg/ha will yield as high as 112 kg/ha, however, a field is seldom entirely weed-free. If ripgut brome is present, increasing seeding rates above 112 kg/ha to reduce wheat yield loss is ineffective. Final constant yield appears to be achieved at 14 a seeding rate of 112 kg/ha; therefore higher seeding rates will not result in increased wheat grain yields.
Equations presented here can be used to estimate yield losses from varied levels of ripgut brome infestation. Such yield loss estimates may be used to evaluate the economic cost of weeds or the economic benefit of a herbicide application. 15
Table 1.1. Comparison of yield regression lines for homogeneity of intercepts and slopesa.
Wheat seeding rate(kg/ha) Wheat seeding rate 56 112 168 224
(kg/ha) (t values)
56 - - -- 0.05 0.06 0.07
112 5.38 ---- 0.02 0.02
168 5.55 1.26 0.02
224 4.05 0.68 0.08 Wm. t(0.05) = 2.45 for 6 df
aValues to the right and left of the dashed lines compare intercepts and slopes, respectively. Table 1.2. Average winter wheat grain yields attained with varied winter wheat seeding rates and ripgut brome densities.
Wheat grain yield
Wheat seeding rate (kg/ha) Average wheat yield at each Ripgut brome ripgut brome density 56 112 168 224 density
(plants/m2) (kg/ha)
0 8140 8390 8130 8350 8250
95 7340 7860 7900 7920 7750
333 5600 7550 7380 6490 6750
653 4480 6590 7070 6920 6270
1170 3260 5250 5400 5500 4860 Average yield at each wheat density: 5760 7130 7180 7040
LSD(0.05) : ripgut brome density = 523; wheat density= 933; all treatment comparisons = 1549 Table 1.3. Effect of brome density and wheat seedingrate on total brome shoot number per unit area.
Total brome shoots
"Brome density (plants/m2) Wheat seeding rate 0 95 333 643 1170
(kg/ha) (number/m2+ SE)
56 0 137+65 286+127 643+_ 66 774+ 73 112 0 223+87 362+165 466+164 479+159
168 0 154+77 387+ 28 446+140 529+ 81
224 0 124+21 266+ 64 356+ 71 486+ 42 9000 9000
8000 - 8000 -
7000 - 7000 -
6000 - 6000 -
5000 - 5000 112 kg/ha
4000 - 4000 = 7615 - 4.0x = 8296 2.6x 3000 - (397) (0.63) 3000 (88) (0.14)
2000 2000 -
1000 1000 -
0 0 0 200 400 600 800 1000 1200 0 200 400 600 800 1000 1200 9000 9000 8000 - 8000 7000 - 7000-
6000 - 6000 - 5000 - 168 kg/ha 5000 - 224 kg/ha 4000 - 4000 - .Y% = 8172 2.2x 9= 8010 - 2.2x 3000 - (145) (0.24) 3000 - (352) (0.58) 2000 - 2 2000 - r= o.97 2 r= 0.83 1000 - 1000
0 0 0 200 400 600 800 1000 1200 0 200 400 600 800 1000 1200 Brome density(plants/m2)
Fi ure 1.1. Effect of brome density on wheat grain yield. Values in parentheses be ow each equation are the standard errors of the intercept and slope, respectively. 00 19
700
600
CV 500
400 - C 4-40 0 _C 300 if) 4-, o 0 56kg/ha ; - 436- 0.23x r2= 0.96 200 (17)(0.027) .... 112kg/ha . .521- 0.21x r2. 0.96 (15)(0.024)
0168kg/ha ; .547- 0.17x r2= 0.84 100 (26)(0.041)
224kg/ha ; =557- 0.12x r2. 0.92 (18)(0.029)
0 200 400 600 800 1000 1200
Brome density(plants/m2)
Figure 1.2. Effect of brome density on total wheat shoot number per unit area. Values in parentheses below each equation are the standard errors of the interceptand slope, respectively. 20
30000
25000 -II
20000
15000
0
0 56kg/ha 9.20600- 10.7x r2.0.96 10000 (827) (1.3)
2 112kg/ha 9=21130 - 7.5x r2=0.95 (639) (1.0)
5000 C1168kg/ha 9=22980- 7.3x r2=0.86 (1057) (1.7)
224kg/ha 9. 22120 - 6.7x r2=0.69 (1594) (2.6)
1 I I 1 1 0 200 400 600 800 1000 1200
Brome density(plants/m2)
Figure 1.3. Effect of brome density on wheat above-ground biomass. Values in parentheses below each equation are the standard errors of the intercept and slope, respectively. 21
LITERATURE CITED
1. Bowden, B. A. and G. Friesen. 1967. Competition of wild oats and flax. Weed Res. 7:349-359.
2. Fischer, B. B., A. H. Lange, and Beecher Crampton. 1983. Growers' weed identification handbook. Univ. Calif. Agric. Ext. Ser., Pub. 4030 WI 67.
3. Godel, G. L. 1935. Relation between rate of seeding and yield of cereal crops in competition with weeds. Sci. Agric. 16:165-168.
4. Hawkes, R. B., T. D. Whitson, and L. J. Dennis. 1985. A guide to selected weeds of Oregon. Oregon Dep. Agric., Oregon State Univ. Page 6.
5. Hitchcock, A. S. 1950. (Revised by A. Chase, 1971.) Manual for the grasses of the United States. Pages 52- 53. 2nd. ed. Dover Publications, Inc., New York.
6. Hufstader, R. W. 1978. Growth rates and phenology of some southern California grassland species. J. Range Manage. 31:465-466.
7. Hull, J. C. and C. H. Muller. 1976. Responses of California annual grassland species to variations in moisture and fertilization. J. Range Manage. 29:49-52.
8. Jain, S. K. 1982. Variation and adaptive role of seed dormancy in some annual grassland species. Bot. Gaz. 143:101-106.
9. Moore, R. J., ed. 1973. Index to plant chromosome numbers 1967-1971. International Bureau for Plant Taxonomy and Nomenclature, Utrecht, Netherlands. Pages 57-58.
10. Smith, D. F. and G. R. T. Levick. 1974. The effect of infestation by Lolium rigidum on yield of wheat. Aust. J. Agric. Res. 25:381-393.
11. Thurston, J. M. 1962. The effect of competition from cereal crops on the germination and growth ofAvena fatua L. in a naturally infested field. Weed Res. 2:192-207.
12. Young, J. A., R. A. Evans, and B. L. Kay. 1973. Temperature requirements for seed germination inan annual-type rangeland community. Agron. J. 65:656-659. 22
Chapter 2. Effect of Depth and Duration of Seed Burial on Ripgut Brome (Bromus rigidus).
ABSTRACT
The influence of depth (0 to 30 cm) and duration (1 to
24 months) of burial on the deterioration, germination, and viability of ripgut brome (Bromus rigidus) seed was studied
in the field. Both surface-sown and buried ripgut brome
seed were depleted within 15 months. Persistence of
surface-sown seed declined slowly during the first year,
falling from 83 to 62 to 23% after 1, 9, and 12 months,
respectively. Seed covered by soil, however, germinated more rapidly, with less than 10% of the initial population ungerminated after 1 month at all depths. The mode of seed disappearance was closely related to whether or not the seed were covered with soil. Seed loss at depths of 1 to 30 cm was primarily due to germination in situ, with little effect
from nonviability loss or enforced or induced dormancy. In contrast, the persistence of surface-sown seed was due primarily to induced dormancy for up to 12 months, with nonviability loss and enforced dormancy becoming important thereafter. Tillage practices aimed at providing favorable germination conditions may effectively reduce ripgut brome
seed survival in the soil. Because seed is relatively
short-lived, seed bank size may be reduced by short-term rotation to a crop that allows for effective control of ripgut brome. 23
INTRODUCTION
Ripgut brome, a winter-annual grass, is a weed problem in rangeland, noncropland, and, to some extent, in cultivated crops. Native to Europe and northern Africa, ripgut brome is now common along the Pacific Coast of North
America from British Columbia to Mexico (2, 7, 8). In winter wheat (Triticum aestivum L.), ripgut brome not only reduces crop growth through competition but also contaminates the grain. Most studies involving ripgut brome have been conducted on the rangelands of the western United States (9, 10, 11,
19). Control programs in winter wheat have been aimed primarily at finding a herbicide to selectively control ripgut brome. Attempts have proven unsuccessfull, partly because both species have similar life cycles, but also, because they have similar susceptibility to several herbicides. Therefore, alternative control strategies are needed. A better understanding of the biology of ripgut brome would be valuable in the design and implementation of more effective control strategies. Other winter-growing annual Bromus species are reported as weeds of crop and rangeland in many agricultural regions of the world. Seed of many of these species exhibit little innate dormancy and germinate rapidly in autumn if favorable conditions exist (1, 6, 20).
IB. D. Brewster, Dep. Crop Sci., Oregon State Univ., Corvallis, OR. Personal communication. 24
The objectives of this study were to determine germination and soil longevity characteristics of ripgut brome and how these characteristics might be used in a control program. 25
MATERIALS AND METHODS
Mature ripgut brome seed were hand-harvested from a field with a history of winter wheat production at the
Oregon State University Botany Farm, near Corvallis, Oregon, in July 1985. Seed were mechanically cleaned, deawned for easier handling, and stored at room temperature until used.
Hereafter, the term 'seed' refers to a complete grass floret including the palea and lemma. The seed population was 100% viable with no dormancy when tested in November 1985. Because of similarities in morphology, ripgut brome (B. rigidus Roth); (2n=42), is often confused with great brome
(B. diandrus Roth); (2n=56), which also is sometimes called ripgut brome (13). Chromosome counts conducted by the
Oregon State University Seed Laboratory, Corvallis, Oregon, verified that the species used in this study was B. rigidus. Prior to burial, each group of 200 seeds was placed in 7.5- by 7.5-cm, 113-mesh polypropylene cloth2 packets that were permeable to water but were impermeable to shoots of germinating seed. Packets were buried in a Woodburn silt loam (fine-silty, mixed, mesic Aquultic Argixeroll) at Hyslop Research Farm near Corvallis, Oregon, on November 11,
1985.
Experimental design was a split-plot replicated in four randomized blocks. Main plots were time increments of 1, 2,
4, 6, 9, 12, 15, 18, 21, and 24 months and subplots were
2Tetko Inc., Elmsford, N.Y. 26 burial depths of 0, 1, 3, 5, 10, 15, 20, and 30 cm. Each subplot was 0.3 by 0.3 m. Surface-sown packets were anchored by a wire through the packet into the soil below to prevent wind disturbance. Packets were not disturbed following burial and the experimental area was kept weed
'free by applying paraquat, 1,1'- dimethyl- 4,4'- bipyridinium ion. To prevent paraquat exposure, surface-sown packets were temporarily protected at application time by an inverted plastic bowl. No supplemental irrigation was provided. Total precipitation was 1020 mm from November 1,
1985, to October 31, 1986 and 880 mm from November 1, 1986, to October 31, 1987. Mean monthly soil temperatures at a depth of 10 cm ranged from 1.2 to 24.7 C from November 1985 to October 1986 and 7.1 to 23.5 C from November 1986 to
October 1987 (Figure 2.1).
Packets were recovered after designated burial durations, allowed to air-dry for 48 h, and analyzed. Recovered seed were partitioned according to Schafer and Chilcote's (15) model (Figure 2.2). Their model was: S= Pex + Pend D g + Dn, where S represented the total number of weed seed buried initially, P the persistent portion of that population, and D the non-persistent portion. The persistent population was divided into two components, seed under enforced dormancy (Pex) and seed under innate or induced dormancy (P ) The non-persistent population was also divided into two components, seed germinating in situ (Dg) and seed losing viability prior to germination (Dn). Partitioning of 27 missing seed (difference between number buried and number recovered) between in situ germination (Dg) and rotted, nonviable (Dn) posed a potential problem because germinated and dead seed are both subject to degradation by soil microorganisms. Seed examined 1, 2, and 4 months after burial were not totally degraded; therefore, none were missing. Partitioning between Dg and Dn was accomplished by counting emerged radicles and testing for nonviable seed with 0.1% (w/v) tetrazolium chloride (5). This established a baseline for Dg and Dn at all depths, which was presumed to be applicable to the remaining buried packets. Seed were missing at month 6, but these numbers corresponded to the number of seed that germinated at month 4 (Dg baseline), and all nonviable and recently germinated seed had not yet deteriorated. None of the nonviable seed had deteriorated beyond distinction within a 6-month period, and therefore Dg and Dn baselines could be modified at each sampling period by partitioning missing seed to D This method of baseline adjustment worked well for partitioning missing seed.
Seed that remained at recovery were used to conduct germination tests. Seed were placed on moistened filter paper in plastic petri dishes and incubated in a growth chamber (dark, 15 C). To determine optimum incubation temperature, germination studies were conducted prior to the burial study in dark growth chambers at four constant temperatures (5, 10, 15, and 20 C). At 2-day intervals for
30 days, germinated seed were counted in fluorescent light 28
at room temperature. Seed germinated at all temperatures but most rapid and complete germination occurred after 6 days at 15 C (data not shown). Final germination counts for seed retrieved from the field were made after 10 days. All seed that germinated in these tests were considered to have been in a state of enforced dormancy (Pex) at the time of recovery. Seed that did not germinate were subjected to tetrazolium tests to distinguish between innate or induced dormancy (Pend)or nonviable (Dn). The partitioning method described was based upon the model suggested by Schafer and
Chilcote (15) (Figure 2.2). 29
RESULTS AND DISCUSSION
Ripgut brome seed was non-dormant at initiation of the
experiment. The almost complete lack of innate dormancy of
ripgut brome seed is similar to that of great brome (6), soft chess (B. mollis L.) (12), poverty brome (B. sterilis
L.)(4), and downy brome (B. tectorum L.)(16, 20). Thus, all ripgut brome seed should germinate when environmental
conditions are suitable.
Seed depletion of ripgut brome was dependent on burial
and duration of burial (Table 2.1). After 1 to 9 months, the majority of ripgut brome seed placed on the soil surface
remained ungerminated, whereas buried seed germinated
rapidly. In fact, only 6 to 10% of the initial population of seed covered by soil remained ungerminated 1 month after burial and less than 1 to 2% remained ungerminated at 9
months . One of the reasons for low germination at the soil surface may be lack of contact with moist soil for sufficient periods of time to allow for germination. Another reason may be inhibition of germination caused by exposure to sunlight. The latter seems unlikely since seed germinated in the laboratory showed no inhibition when exposed to light. Seed populations, however, were totally depleted at all depths 15 months following initiation of the experiment. No effect of depth on seed persistence was observed for seed buried 1 to 30 cm.
In situ germination (Dg) and, to a lesser extent, 30
nonviability loss (Dn) were the modes by which buried (1 to
30 cm) seed were lost from the population. After 1 month, in situ germination occurred readily at all depths except
for surface-sown seed (Table 2.2). In general, environmental conditions were favorable, namely
precipitation, to allow for maximum germination during late
fall and early winter. Nonviability loss in ungerminated seed accounted for no more than 11% of the seed population after 15 months (Table 2.3).
In contrast, in situ germination and nonviability loss were minimal for surface-sown seed up to 9 and 12 months,
respectively (Tables 2.2 and 2.3). Probably, the same conditions that prevented in situ germination, e.g., poor soil moisture contact, also contribute to low nonviability loss. Seed not continuously exposed to moisture have a lower chance of decay or disease attack. After 15 months, loss due to nonviable seed increased dramatically. This increase coincides with the lose of induced dormancy in the population, as well as exposure to cooler temperatures and increased precipitation which may have lead to freezing damage.
Buried and surface-sown seed of ripgut brome were regulated by two types of dormancy. Seed persistence was due primarily to induced dormancy (Fend)'especially for the survival of surface-sown seed (Table 2.5). Induced dormancy, however, was of short duration and was not observed after 12 months' burial. Induced dormancy iscommon 31
in seed of downy brome (18, 20) and also has been observed
in poverty brome seed exposed to light (14). Enforced dormancy (Pex) was a minor factor in seed persistence (Table 2.4). The highest degree of enforced dormancy was observed
in surface-sown seed (8%), probably as a result of poor soil
contact and thus insufficient moisture to germinate.
Ripgut brome has germination and soil longevity
characteristics similar to other winter annual Bromus
species (1, 6, 20). Knowledge of these characteristics can
be used to develop effective control measures. Because of the lack of innate dormancy, almost complete germination of the soil seed bank could be achieved by providing favorable
germination conditions. Because surface-sown seed exhibit induced dormancy, a light cultivation or harrowing in autumn to bury seed from the soil surface would help prevent
induced dormancy. Early tillage has been recommended for
improving germination of great brome (6), downy brome (17), and poverty brome (3) prior to cultivation or herbicide
treatment. The fact that ripgut brome seed germinated even
at the 30-cm depth, but almost certainly could notemerge from that depth, explains the well-knownsuccess of moldboard plowing in reducing brome populations.
A delay in wheat planting may be necessary toensure
complete germination of ripgut brome. This delay would not need to be long (15 months) when seed is buried and
conditions are suitable for germination. An excessive delay, however, may reduce wheat yield. 32
Crop rotation may effectively reduce the density and
prevent the increase of ripgut brome in winter wheat. Rotation allows the use of control measures such as tillage
and/or herbicides that are either unavailable or ineffective
in winter wheat. Additionally, seed bank size will be reduced because ripgut brome plants that can not become
established will not produce seed to replenish the seed bank and seed already present is relatively short-lived.
Environmental conditions played a central role in influencing the changes that occurred in the ripgut brome
seed bank. Seasonal fluctuations may alter the rates of
seed disappearance, but modes of loss should be similar.
Thus, control recommendations should be applicable to winter wheat producing areas with a winter rainfall pattern. 33
Table 2.1. Effect of depth and duration of burial on persistence (Pex + Pen d ) of ripgut brome seeda.
Persistence of ripgut brome seed buried at various depths (cm) Burial duration (monthsb) 0 1 3 5 10 15 20 30
(% + SE of initially buried seed)
1 83+4 8+3 10+3 9+3 6+2 6+1 7+2 7+4
2 78+3 3+1 15+6 8+4 3+1 3+1 3+2 4+5
4 60+6 2+1 2+1 1+1 2+2 2+1 3+1 2+1
6 68+5 1+1 1+1 2+2 <1+<1 1+1 <1+1 0
9 62+3 <1+<1 1+1 1+1 1+<1 2+1 1+<1 2+<1
12 23+5 <1+<1 2+3 0 1+1 0 <1+<1 1+1
15 0 0 0 0 0 0 0 0
18 0 0 0 0 0 0 0 0
21 0 0 0 0 0 0 0 0
24 0 0 0 0 0 0 0 0
aValues presented are means of four replications of 200 seeds each.
bMonths following November 11, 1985. 34
Table 2.2. Effect of depth and duration of burial on in situ germination (Dg) of ripgut brome seeda.
In situ germination of ripgut brome seed buried at various depths (cm) Burial duration (monthsb) 0 1 3 5 10 15 20 30
(% + SE of initially buried seed)
1 5+2 82+3 80+3 81+5 88+3 89+2 88+2 87+4
2 8+4 85+4 78+4 83+6 91+2 93+4 92+2 89+6
4 25+7 91+4 92+5 94+3 96+1 95+2 92+3 93+2
6 14+6 91+2 94+2 90+1 92+2 93+2 94+2 93+2
9 21+3 90+1 93+1 90+1 92+2 92+1 93+2 91+2
12 62+7 91+1 90+2 92+1 93+1 92+2 93+2 93+2
15 66+3 91+1 90+2 92+1 93+1 92+2 93+2 93+2
18 66+3 91+1 90+2 92+1 93+1 92+2 93+2 93+2
21 66+3 91+1 90+2 92+1 93+1 92+2 93+2 93+2
24 66+3 91+1 90+2 92+1 93+1 92+2 93+2 93+2
aValues presented are means of four replications of 200 seeds each.
bMonths following November 11, 1985. 35
Table 2.3. Effect of depth and duration of burial on nonviability loss (Dn) of ripgut brome seeda.
Nonviability loss of ripgut brome seed buried at various depths (cm) Burial duration (monthsb) 0 1 3 5 10 15 20 30
(% + SE of initially buried seed)
1 12+3 10+2 10+4 10+3 6+2 5+1 5+2 6+1
2 14+2 12+4 7+2 10+7 6+1 5+2 5+1 7+1
4 15+1 8+4 6+5 5+2 3+1 3+1 5+2 5+1
6 18+3 8+2 6+2 7+2 8+2 6+2 6+2 7+2
9 17+2 9+1 6+1 9+1 8+1 6+1 6+2 7+2
12 15+5 9+1 9+4 8+1 6+1 8+2 7+2 6+2
15 34+3 9+1 10+2 8+1 7+1 8+2 7+2 7+2
18 34+3 9+1 11+2 8+1 7+1 8+2 7+2 7+2
21 34+3 9+1 11+2 8+1 7+1 8+2 7+2 7+2
24 34+3 9+1 11+2 8+1 7+1 8+2 7+2 7+2
aValues presented are means of four replications of200 seeds each.
bMonths following November11, 1985. 36
Table 2.4. Effect of depth and duration of burial on enforced dormancy ( Pex) of ripgut brome seeda.
Persistence of ripgut brome seed buried at various depths (cm) Burial duration (monthsb) 0 1 3 5 10 15 20 30
(% + SE of initially buried seed)
1 8+4 4+3 4+3 4+2 1+1 2+1 2+1 2+1
2 8+5 1+1 3+1 1+1 <1+<1 <1+<1 <1+1 <1+<1
4 1+1 2+1 1+1 1+<1 1+<1 1+1 2+1 1+1
6 2+2 1+<1 1+<1 <1+<1 0 <1+<1 <1+1 0
9 2+1 <1+<1 <1+<1 1+1 <1+<1 1+1 <1+<1 1+<1
12 3+<1 0 <1+1 0 0 0 0 0
15 0 0 0 0 0 0 0 0
18 0 0 0 0 0 0 0 0
21 0 0 0 0 0 0 0 0
24 0 0 0 0 0 0 0 0
aValues presented are means of four replications of 200 seedseach.
bMonths following November11, 1985. 37
Table 2.5. Effect of depth and duration of burial on induced dormancy (Pend) of ripgut brome seeda.
Persistence of ripgut brome seed buried at various depths (cm) Burial duration (monthsb) 0 1 3 5 10 15 20 30
(% + SE of initially buried seed)
1 73+5 3+2 5+2 4+3 4+2 3+1 5+3 5+2
2 69+2 1+1 12+5 6+5 3+1 2+2 3+1 3+5
4 59+6 0 1+1 <1+<1 1+1 1+1 0 <1+<1
6 66+4 <1+<1 <1+<1 2+2 <1+<1 <1+<1 <1+1 . 0
9 61+4 .0 1+<1 <1+<1 <1+<1 1+1 1+<1 1+1
12 19+5 <1+<1 2+3 0 1+1 0 <1+<1 1+1
15 0 0 0 0 0 0 0 0
18 0 0 0 0 0 0 0 0
21 0 0 0 0 0 0 0 0
24 0 0 0 0 0 0 0 0
aValues presented are means of four replications of 200 seedseach.
'Months following November 11, 1985. 38
300
250 E 200 0 150 ca C.) 100 a) 0 50
0
0 2I
14
7 0 Ln
0 0 3 6 9 12 15 18 22 Nov Feb May Aug Nov Feb May Aug Time ( months )
Figure 2.1. Monthly precipitation and mean monthly soil temperature at a depth of 10 cm from November 1985 to October 1987 recorded at Hyslop Research Farm near Corvallis, Oregon. 39
INITIAL POPULATION
ROTTED NONVIABLE GERMINATION SEED ( Dn ) (Dg) RECOVERED POPULATION
GERMINATION TESTS Germination/ No Germination
ENFORCED VIABILITY (TZ) DORMANT TESTS PeX) Positive Negative
INDUCED NONVIABLE OR INNATE (Dr ) DORMANT ( Pend)
Figure 2.2. Model used to partition weed seed recoveredfrom and depletion soil into components of persistence (Pex end) (Dg + Do). 40
LITERATURE CITED
1. Budd, E. G. 1981. Survey, dormancy and life cycle of Bromus sterilis (sterile brome) in cereals, with particular reference to spring barley. J. Nat. Inst. Agric. Bot. 15:430-439.
2. Fischer, B. B., A. H. Lange, and B. Crampton. 1983. Growers' weed identification handbook. Univ. Calif. Agric. Ext. Ser., Pub. 4030 WI 67.
3. Froud-Williams, R. J. 1983. The influence of straw disposal and cultivation regime on the population dynamics of Bromus sterilis. Ann. Appl. Biol. 103:139- 148.
4. Froud-Williams, R. J., R. J. Chancellor, and D. S. H. Drennan. 1984. The effects of seed burial and soil disturbance on emergence and survival of arable weeds in relation to minimal cultivation. J. Appl. Ecol. 21:629-641.
5. Grabe, D. F. 1970. Tetrazolium Testing Handbook. Contribution 29 to the Handbook on Seed Testing, Association of Official Seed Analysts.
6. Harradine, A. R. 1986. Seed longevity and seedling establishment of Bromus diandrus Roth. Weed Res. 26:173-180.
7. Hawkes, R. B., T. D. Whitson, and L. J. Dennis. 1985. A guide to selected weeds of Oregon. Oregon Dep. Agric., Oregon State Univ. Page 6.
8. Hitchcock, A. S. 1950. (Revised by A. Chase, 1971.) Manual of the grasses of the United States. 2nd. ed., Dover Publications, Inc., New York. Pages 52-53.
9. Hufstader, R. W. 1978. Growth rates and phenology of some southern California grassland species. J. Range Manage. 31:465-466.
10. Hull, J. C. and C. H. Muller. 1976. Responses of California annual grassland species to variations in moisture and fertilization. J. Range Manage. 29:49-52.
11. Jain, S. K. 1982. Variation and adaptive role of seed dormancy in some annual grassland species. Bot. Gaz. 143:101-106.
12. McGowan, A. A. 1970. Comparative germination patterns of annual grasses in north-eastern Victoria. Aust. J. 41
Exp. Agric. Anim. Husb. 10:401-404.
13. Moore, R. J., ed. 1973. Index to plant chromosome numbers 1967-1971. International Bureau for Plant Taxonomy and Nomenclature, Utrecht, Netherlands. Pages
57-58. .
14. Pollard, F. 1982. Light induced dormancy in Bromus sterilis. J. Appl. Ecol. 19:563-568.
15. Schafer, D. E. and D. 0. Chilcote. 1969. Factors influencing persistence and depletion in buried seed populations. I. A model for analysis of parameters of buried seed persistence and depletion. Crop Sci. 9:417-418.
16. Thill, D. C., K. G. Beck, and R. H. Callihan. 1984. The biology of downy brome (Bromus tectorum). Weed Sci. 32:suppl. 1, 7-12.
17. Wicks, G. A. 1984. Integrated systems for control and management of downy brome (Bromus tectorum) in crop land. Weed Sci. 32:suppl. 1, 26-31.
18. Wicks, G. A., 0. C. Burnside, and C. R. Fenster. 1971. Influence of soil type and depth of planting on downy brome seed. Weed Sci. 19:82-86.
19. Young, J. A., R. A. Evans, and B. L. Kay. 1973. Temperature requirements for seed germination in an annual-type rangeland community. Agron. J. 65:656-659.
20. Young, J. A., R. A. Evans, and R. E. Eckert. 1969. Population dynamics of downy brome. Weed Sci. 17:20- 26. 42
Chapter 3. Vernalization Requirements for Flowering of Ripgut Brome (Bromus rigidus)
ABSTRACT
Ripgut brome (Bromus rigidus Roth) has a quantitative requirement for vernalization in order to flower. In greenhouse studies, cold treatment (5 + 2 C) of 2, 4, or 6 weeks shortened the vegetative period, but longer exposure did not further decrease the time required to flower. Plants vernalized as imbibed seed for 8 weeks took 17 days to flower following transfer from cold treatment to the greenhouse. Unvernalized controls flowered 53 days after planting in the greenhouse. Highest total seed dry weight and total shoot dry matter was produced by unvernalized plants; lengthening periods of vernalization from 2 to 8 weeks decreased both measurements. The ratio of total seed dry weight to total shoot dry weight was significantly greater for vernalized plants than unvernalized controls. In field studies, ripgut brome plants established in the fall flowered sooner after resumption of growth in the spring than those planted in the spring. Plants seeded after April failed to flower until the following spring. 43
INTRODUCTION
Ripgut brome, a winter annual grass, is found in rangeland, noncropland, and occasionally in cultivated crops. Native to Europe and northern Africa, ripgut brome is now quite common along the Pacific Coast of North America
from British Columbia to Mexico (7, 8). This weed reduces crop growth through competition and at maturity caneither contaminate harvested grain or, if grazed, cause nose and eye injury to livestock because of its long awns (6).
Research on ripgut brome has been limited primarily to
requirements for germination (12, 19) and management
practices for its use in annual grasslands (9, 11). Control programs in winter wheat (Triticum aestivum L.) have focused on selective control with herbicides but attempts have been unsuccessfull. Additional information on the biology of ripgut brome may suggest ways to manage it in winter wheat.
The literature on vernalization requirements for flowering has been reviewed previously (3, 4, 13, 15, 18).
Vernalization is the acquisition or acceleration of the
ability to flower by a chilling treatment (3). It is a "preparatory process" to flowering, but is not the flower
initiation process itself. Thus, vernalization merely
confers responsiveness to stimuli that initiate flowering
and can be measured only as an aftereffect following the end
1B. D. Brewster, Dep. Crop Sci., Oregon State Univ., Corvallis, OR. Personal communication. 44 of a cold treatment. Vernalization requirements may be either qualitative (absolute) if they have an all-or-none effect or quantitative (facultative) if they simply hasten floral initiation. Plants with a quantitative requirement can be vernalized as imbibed seed, whereas those with a qualitative requirement must undergo a juvenile phase before cold treatment is effective (2).
Winter wheat has a quantitative requirement for vernalization (18). Trione and Metzger (17) observed that the effectiveness of vernalization for winter wheat seedlings was maximum at 7 C but decreased very rapidly if raised to 9 C or lowered to 3 C.
Downy brome (B. tectorum L.), a winter-annual weed in winter wheat, has a quantitative requirement for vernalization. Finnerty and Klingman (5) found that downy brome plants flowered within 100 days following vernalization of caryopses at 3.3 C for 25 or 30 days.
Additionally, an inductive period of seed vernalization or short days followed by long days was required for panicle production. Flowering was inhibited when plants were exposed to short days following vernalization. Plants also failed to produce panicles when exposed to continuous short or long days.
The objective of this study was to determine the vernalization requirements for flowering of ripgut brome under both greenhouse and field conditions. 45
MATERIALS AND METHODS
Vernalization of imbibed seed. The objectives of this experiment were to determine whether ripgut brome required vernalization in order to flower and whether imbibed seed could be vernalized. Mature ripgut brome seed were hand- harvested from a field with a history of winter wheat production at the Oregon State University Botany Farm, near
Corvallis, Oregon, in July 1985. Seed were mechanically cleaned, deawned for easier handling, and stored at room temperature until used. Hereafter, the term 'seed' refers to a complete grass floret including the palea and lemma.
The seed population was 100% viable with no dormancy when tested in November 1985.
Because of similarities in morphology, ripgut brome (B. rigidus Roth; 2n=42) is often confused with great brome (B. diandrus Roth; 2n=56), which also is sometimes called ripgut brome (14). Chromosome counts conducted by the Oregon State University Seed Laboratory, Corvallis, Oregon, verified that the species used in the study was B. rigidus.
Ripgut brome seed were placed in 100 by 100 by 15 mm petri dishes containing blotter paper moistened with deionized water. Dishes were wrapped in aluminum foil to exclude light and the seed were kept moist by periodic addition of deionized water at which time seed were exposed to fluorescent room lighting. Ripgut brome seed were chilled in a cooler at 5 + 2 C for 0, 2, 4, 6, or 8 weeks 46 before transplanting into a potting soil.Vernalization treatments were staggered so that all were terminated at the same time. At the end of vernalization, the 8-, 6-, 4-, and 2- week -old vernalized seed had germinated. To prevent devernalization, seed (0-week-vernalization) and seedlings were stored in the dark at 15 C for 5 days before transplanting. During this time the unvernalized seed also germinated. Three uniform seedlings were transplanted into each pot (15.2 cm diam by 17.8 cm, 3.0 L soil). Potted plants were fertilized with a slow-release granular fertilizer (18:6:12, N:P:K) and were subirrigated. The potting mixture was soil, peat, sand, and pumice (1:1:1:2, v/v/v/v; pH 6.5). After establishment, the plants were thinned to one plant per pot.
The dates of planting, seedling emergence, and the first emergence of the awns through the boot were recorded. The time of awn emergence was chosen as a relative measure of the rate of flowering and was observed three times a week. The exact time of floral initiation can be determined only by microscopic observations over time, which was not done in this study. Observation of awn emergence does not discriminate between the component processes of flowering, such as floral initiation and later floral development. It also overestimates the time that plants remain vegetative.
Rates of awn emergence and both floral initiation and development were assumed to be influenced similarly by 47 vernalization (2). Plants were harvested at maturity and the number of cuims (main shoot and tillers), plant height (measured from
soil surface to tip of uppermost leaf), total seed dry weight per plant, and total shoot dry weight per plant were determined. As seed matured, they were removed, oven dried
at 70 C for 48 h, and weighed. This and the next greenhouse experiment were conducted
concurrently from October 1985 to May 1987. Sunlight was supplemented with fluorescent lighting to provide at least a
16-h photoperiod throughout the year. Light intensity was between 95 and 165 uEm-2s-1 at the soil surface. Day and night temperatures were approximately 21 and 16 C,
respectively. A randomized complete block design with 20 plants
(replication) per treatment was used for all greenhouse and
field experiments. All three experiments were conducted
twice. Analyses of variance were computed for pooled data, and differences between means were compared using Fisher's protected Least Significant Difference (LSD) Test at the
0.05 level of significance.
Duration of vernalization of seedlings. A field experiment was conducted on the effect of various durations of
vernalization outdoors on the flowering behavior of
established seedlings. Plants were established outdoors in
pots in October and taken into the greenhouse at monthly
intervals throughout the winter. 48
Experiments were established on October 25, 1985 and
1986, in order to minimize the effect of seasonal changes in photoperiod and weather. One hundred forty pots of ripgut brome were started outdoors at Hyslop Research Farm near
Corvallis, Oregon, in 1985 and at Oregon State University,
Corvallis, Oregon, in 1986. Ten to 20 nondormant seeds were sown 2.5 cm deep in a Woodburn silt loam (fine-silty, mixed, mesic Aquultic Argixeroll) collected from Hyslop Research
Farm. To prevent freezing damage, pots were partially buried in soil or peat to within 2.5 cm of the top of the top. Before the onset of winter, plants were thinned to three seedlings per pot and fertilized, as described previously. At the same time that plants were started outdoors, seed were sown in 20 pots in the greenhouse to serve as the unvernalized control. When the 20 pots of vernalized ripgut brome were brought indoors, they were thinned to one plant per pot. Maximum and minimum air temperatures were obtained from an official weather station near the experimental sites
(Table 3.1). The experimental design, statistical analysis, and plant measurements were the same as in the previous experiment.
Season of establishment of seedlings. A field experiment was established to determine the effect of planting date on the flowering behavior of ripgut brome. At monthly intervals from October 1985 to May 1986, 20 pots of ripgut 49 brome were planted outdoors. The sites, environmental conditions, potting soil, and planting procedure were the same as in the previous field experiment. In the spring, fall plantings and all subsequent plantings were thinned to one seedling per pot. Date of seedling and awn emergence through the boot were recorded three times weekly. The experimental design and plant measurementswere the same as previously described. 50
RESULTS AND DISCUSSION
Vernalization of imbibed seed. Low-temperature treatment of imbibed ripgut brome seed modified the maturation and flowering biology of this weed in the greenhouse. Cold treatment for up to 6 weeks shortened the vegetative period, but increasing the treatment from 6 to 8 weeks did not further decrease the time required for flowering (Table
3.2). Unvernalized plants needed more time to mature, after placing them into suitable growing conditions, than plants that were cold treated. Imbibed seed that had been vernalized for 8 weeks flowered 17 days after transfer to favorable growing conditions, whereas unvernalized controls flowered only after 53 days. This shows that ripgut brome has a quantitative requirement for vernalization.
Number of culms per plant tended to increase as the length of vernalization increased (Table 3.2). In general, unvernalized plants were taller than vernalized plants
(Table 3.2).
Highest total seed dry weight and total shoot dry matter were produced by unvernalized plants (Table 3.2).
Increasing periods of cold treatment caused a decrease in both total seed and shoot dry matter. Treatment longer than
6 and 4 weeks, however, did not cause further reductions in total seed and shoot dry matter, respectively. Unvernalized ripgut brome produced three times as much total seed weight and eight times as much total shoot dry matter as plants 51 receiving 8 weeks of cold treatment.
Dry weight distribution to reproductive tissue differed among unvernalized and vernalized plants. Cold-treated plants allocated significantly more dry matter to reproductive tissue than the unvernalized controls (Table
3.2).
Duration of vernalization of seedlings. Determination of the vernalization response using imbibed seed assumes that the seed response and that of the vegetative plant are similar (16). Seed that were vernalized at 5 C + 2 C in a cooler for 8 weeks matured faster (17 days) than seedlings that were chilled outdoors for 8 weeks (32 days) after transfer to the greenhouse (Table 3.2 and 3.3). One possible explanation for the difference in flowering times is devernalization. If seedlings are placed in a warm environment immediately after cold treatment, devernalization may occur (13). Under field conditions, where environmental conditions are not controlled and diurnal fluctuation is common, the actual physiological response is probably an integration of the individual fast, slow, and devernalization reactions that may occur (17). All of the plants that were vernalized outdoors had flowered by the end of the experiment. Unvernalized plants started in October (0 weeks vernalized) in the greenhouse took 66 days to flower. Thus, ripgut brome does not have an obligate requirement for vernalization in order to flower.
The time needed for ripgut brome to flower, once plants 52 were brought into the greenhouse, depended upon the duration of chilling outdoors (Table 3.3). Increased periods of cold treatment reduced the time needed for established plants to mature and flower. In fact, seedlings vernalized for 30 weeks flowered in the field before transfer to the greenhouse. As observed in the greenhouse experiment, the number of culms per plant tended to decrease as the length of vernalization increased (Table 3.3). Additionally, highest yields of total shoot and seed dry weight were produced by . unvernalized controls. Vernalized plants allocated a significantly higher percentage of dry matter to reproductive tissue than did the unvernalized controls.
Season of establishment of seedlings. Results of this field experiment verified and extended the observations made in the first two experiments. Plants started in October through April were vernalized either as established seedlings or imbibed seed and flowered during spring or summer, but plants started after this time did not flower until the following spring. Hulbert (10) found that winter plantings of downy brome at Lewiston, Idaho, flowered normally in June. Plants from March, April, and May seedings failed to produce panicles in the summer.
Plants that were started in the fall flowered sooner after resumption of growth in the spring than those started in the spring (Figure 3.1). Plants started in October to
December all flowered in late April. 53
Ripgut brome seeded as late as April emerged and flowered by mid-July. Seed planted in May failed to germinate until September and did not flower until the following spring. Failure to germinate may be because of the warmer and drier conditions of approaching summer and not until favorable conditions returned in the fall does germination occur. If seed should germinate in late spring, however, it is unlikely that plants would set seed in the year of establishment because day length would be short before flowering could occur. Therefore, seedbed preparation in the fall before winter wheat planting would kill established, unvernalized plants prior to flowering.
In contrast, small plants overwintering as seedlings or vernalized as imbibed seed and germinating in the spring would have adequate time to flower, mature, and shed seed before winter wheat harvest. Vernalization requirements for flowering also may be an adaptation to dry summer habitats (1). Alyssum alyssoides L., a winter annual, must be vernalized in order to complete its life cycle before the onset of summer drought.
Unvernalized plants are more likely to die during summer drought before they are able to flower. Many of the winter annual weeds of winter wheat including ripgut brome complete their life cycles either before or with winter wheat (5) thus avoiding adverse summer conditions. 54
Table 3.1. Mean daily maximum and minimum monthly air temperature recorded at Hyslop Research Farm near Corvallis, Oregon.
1985-86 1986-87 Month Maximum Minimum Maximum Minimum
(C) (C)
Oct. 17.8 5.0 18.3 7.2
Nov. 7.2 0.0 15.6 4.4
Dec. 4.4 -3.3 7.8 0.6
Jan. 10.0 2.2 7.8 0.6
Feb. 10.0 2.8 11.1 2.8
Mar. 15.6 5.6 13.3 3.9
Apr. 15.0 3.9 18.3 4.4
May 18.9 7.2 21.1 7.8 55
Table 3.2. Effect of vernalization duration at 5 C on days to flowering, culms per plant, plant height, total seed dry weight, total shoot dry weight per plant, and the ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhousea.
Total seedTotal shoot Ratio of Duration of Time to Culms perPlant dry weightdry weight seed dry wt/ vernalizationflowering plant heightper plant per plant shoot dry wt
(weeks) (days) (no.) (cm) (g) -(g /g) - - --
0 52.8 35.4 75.9 22.4 20.7 1.20
2 29.1 32.1 61.9 12.4 6.9 1.98
4 21.6 30.2 49.2 9.0 4.1 2.35
6 17.8 25.1 41.7 7.1 2.7 2.81
8 16.7 29.3 39.6 7.1 2.6 2.86
LSD(0.05) 1.2 4.2 4.6 1.4 1.7 0.21
aValues are means averaged over two years (N=40). 56
Table 3.3. Effect of outdoor cold treatment on days to flowering, culms per plant, total seed dry weight, total shoot dry weight per plant, and the ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhousea.
Total seedTotal shoot Ratio of Duration of Time to Culms perdry weightdry weight seed dry wt/ vernalization flowering plant per plant per plant shoot dry wt
..(gig)....._ (weeks) (days) (no.) (g)
0 65.9 46.8 21.2 32.5 0.70
4 28.3 28.9 11.2 5.0 2.50
8 31.7 24.3 11.5 4.5 2.63
12 27.9 20.7 8.5 3.8 2.28
16 22.4 21.5 7.9 5.0 1.80
20 22.2 22.8 9.9 5.5 2.13
24 8.4 18.3 9.5 6.6 1.60
30 0.0 18.9 18.4 10.9 1.81
LSD(0.05) 3.4 5.1 2.4 2.4 0.52
a Valuesare means averaged over two years (N=40). 57
THIS PAGE LEFT BLANK INTENTIONALLY Oct NovDec Jan FebMarAprMay Jun Jul Aug Sep Apr 10 20 3010 20 30 10 20 30 10 20 3010 20 28 10 20 30 10 20 3010 20 3010 20 30 10 203010 20 3010 20 30 10 20 30
1 1 I I I I I I I 1 I I 1 I 1 I I 1 1 1 1 1 1 1 I I 1 Mal Headed
. 7 Planted ZAE1E1 7 Emerge I ,/ 131 KAU All v AME3 . /0 333
1Numerals in blocks indicate days from planting to heading.
Figure 3.1. Effect of date of planting in the field on the emergence and flowering of ripgut brome 59
LITERATURE CITED
1. Baskin, J. M. and C. C. Baskin. 1974. Effect of vernalization on flowering of the winter annual Alyssum alyssoides. Bull. Torrey Bot. Club 101:210-213.
2. Bernier, G., J. M. Kinet, and R. M. Sachs. 1980. The Physiology of Flowering, V61.1. Initiation of Flowers. CRC Press, Boca Raton, FL. 176 pp.
3. Chouard, P. 1960. Vernalization and its relations to dormancy. Annu. Rev. Plant Physiol. 11:191-238.
4. Evans, L. T., ed. 1969. The Induction of Flowering: Some Case Histories. Cornell Univ. Press, New York. 488 pp.
5. Finnerty, D. W. and D. L. Klingman. 1962. Life cycles and control studies of some weed bromegrasses. Weeds. 10:40-47.
6. Fischer, B. B., A. H. Lange, and B. Crampton. 1983. Growers' weed identification handbook. Univ. Calif. Agric. Ext. Ser., Pub. 4030 WI 67.
7. Hawkes, R. B., T. D. Whitson, and L. J. Dennis. 1985. A guide to selected weeds of Oregon. Oregon Dep. Agric., Oregon State Univ. Page 6.
8. Hitchcock, A. S. 1950. (Revised by A. Chase, 1971.) Manual of the grasses of the United States. 2nd. ed. Dover Publications, Inc., New York. Pages 52-53.
9. Hufstader, R. W. 1978. Growth rates and phenology of some southern California grassland species. J. Range Manage. 31:465-466.
10. Hulbert, L. C. 1955. Ecological studies of Bromus tectorum and other annual bromegrasses. Ecol. Monogr. 25:181-213.
11. Hull, J. C. and C. H. Muller. 1976. Responses of California annual grassland species to variations in moisture and fertilization. J. Range Manage. 29:49-52.
12. Jain, S. K. 1982. Variation and adaptive role of seed dormancy in some annual grassland species. Bot. Gaz. 143:101-106.
13. Lang, A. 1965. Physiology of flower initiation. In W. Ruhland, ed. Encycl. Plant Physiol. 15:1380-1536.
14. Moore, R. J., ed. 1973. Index to plant chromosome 60
numbers 1967-1971. International Bureau for Plant Taxonomy and Nomenclature, Utrecht, Netherlands. Pages 57-58.
15. Purvis, 0. N. 1966. The physiological analysis of vernalization. In W. Ruhland, ed. Encycl. Plant Physiol. 16:76-122.
16. Silsbury, J. H. 1964. The effect of vernalization on the heading of Wimmera ryegrass (Lolium rigidum) and on five cultivars of perennial ryegrass (Lolium perenne). Aust. J. Exp. Agric. Anim. Husb. 4:352-356.
17. Trione, E. J. and R. J. Metzger. 1970. Wheat and barley vernalization in a precise temperature gradient. Crop Sci. 10:390-392.
18. Vince-Prue, D. 1975. Photoperiodism in Plants. McGraw-Hill Book Co., New York. Pages 262-291.
19. Young, J. A., R. A. Evans, and B. L. Kay. 1973. Temperature requirements for seed germination in an annual-type rangeland community. Agron. J. 65:656-659. 61
GENERAL DISCUSSION
Results from this study provide a good starting point for understanding the biology of ripgut brome, as well as providing a useful method for its control. Although these findings are based on winter wheat production in the
Willamette Valley of western Oregon, they may be applicable in other areas with a winter rainfall pattern. Seasonal fluctuations also will influence the results but general principles should remain similar.
Although generally accepted that the presence of weeds in a field reduces crop yield, quantification of this yield loss is important. Equations presented in Chapter 1 can be used to estimate yield losses from varied levels of ripgut brome infestation and determine the economic cost of ripgut brome. An additive design was used in Chapter 1 to determine directly the cost (crop loss) that is associated with the absence of weed control. This information is of immediate practical agronomic value and met the objectives of the study. This design does not allow us to determine the degree of interaction either between species or among individuals of the same species. A substitutive design
(replacement series) would have provided these answers
(Radosevich and Holt, 1984). The substitutive design requires that total density remain constant while the two species occur in varying proportions ranging from 0 to 1.0. 62
Although a more accurate assessment of competitiveness can be achieved using a substitutive rather than the additive design, a substitutive design is not without disadvantages. Under most field conditions, crop density is fixed and does not vary much, thus the use of a substitutive design would be somewhat artificial.
One of the objectives of Chapter 1 was to estimate maximum yield loss potential at each wheat seeding rate. As ripgut brome density increased, even up to 1170 plants/m2, yield loss was only beginning to plateau at the 56 kg/ha wheat seeding rate and was still increasing at the higher seeding rates (112, 168, and 224 kg/ha). Therefore, brome density would need to be increased in order to determine maximum yield loss potential. These brome densities are not uncommon in grower fields in western Oregon.
Perhaps the most encouraging information for control of ripgut brome is presented in Chapter 2. Ripgut brome seed is relatively short-lived in the soil. Both surface-sown and buried seed were depleted within 15 months. After 1 month of burial, over 80% of the initially buried seed germinated at depths of 1 to 30 cm, whereas only 5% of the surface-sown seed germinated. Obviously, seed covered by soil were placed into environmental conditions that were favorable for germination. Therefore, a light cultivation or harrowing in autumn to bury seed from the soil surface would encourage brome germination and allow the removal of germinated seedlings by cultivation before wheat was 63 planted, assuming adequate autumn rainfall is received.
Crop rotation may effectively reduce the density and prevent the increase of ripgut brome in winter wheat. For example, successful brome control has been achieved at
Hyslop Farm near Corvallis, Oregon, with a two-year rotation of Austrian peas or red clover. This rotation has allowed the use of the herbicide pronamide, 3, 5-dichloro(N-1,1- dimethy1-2-propynyl)benzamide, which is registered for brome control in Austrian peas and red clover but is not selective in winter wheat. Even a one year rotation to Austrian peas followed by wheat was effective in reducing brome levelsl.
Take-all, caused by the fungus Gaeumannomyces graminis (Sacc.) Arx and Olivier var. tritici Walker, is a major root disease of wheat and a problem for growers in the Willamette
Valley of western Oregon. Fields under continuous wheat production undergo a process called take-all decline. This is a gradual increase in a natural biological control of the disease. The first year of wheat production is unaffected by the disease followed by several years of poor yields because of take-all and then a return to yields similar to the first year of production. Rotation out of wheat for brome control would require that take-all decline occur again. Therefore, before rotating to another crop, yield loss due to brome must be weighed against that caused by take-all.
Ripgut brome seed were buried in packets that were
B. D. Brewster, Dep. Crop Sci., Oregon State Univ., Corvallis, OR. Personal communication. 64 permeable to water but were impermeable to shoots of germinating seed. Had the packets allowed shoots to penetrate, depth of emergence also could have been studied.
The fact that seed germinated even at the 30-cm depth, but almost certainly could not emerge from that depth, explains the well-known success of moldboard plowing in reducing brome population. Certainly a primary concern of seed burial studies is the ability to retrieve the buried packets and its contents. Although ripgut brome seed are relatively
long in length, they are rather narrow in width. Selection
of a larger mesh size may have allowed penetration of
germinating shoots but at the same increased the chance of
seed loss at retrieval. Further study needs to be conducted to determine what
factors are preventing the germination of surface-sown packets. The burial packet may have prevented adequate soil contact, thus inhibiting water uptake and germination.
Additionally, exposure to sunlight also may be inhibitory.
The role of light in germination needs to be clarified. Ripgut brome does not have to be vernalized in order to
flower. Therefore, seeds germinating in the spring and not vernalized can still produce seed that will contribute to the following season's weed problem. Fall tillage, however, would bury this seed, promote germination, and allow for cultivation before wheat is planted.
Little literature exists on the biology and life cycle of ripgut brome, especially in cultivated crops. I hope 65 that the research presented here will provide a foundation for the continuation of further studies. For example, the result of ripgut brome density on winter wheat grain yield is known, but we do not know the mechanisms involved in this process. Mathematical growth analysis may provide information for understanding the basis of differential success when crop and weed are grown together. 66
BIBLIOGRAPHY
Baskin, J. M. and C. C. Baskin. 1974. Effect of vernalization on flowering of the winter annual Alyssum alyssoides. Bull. Torrey Bot. Club 101:210-213.
Bernier, G., J. M. Kinet, and R. M. Sachs. 1980. The Physiology of Flowering, Vol.l. Initiation of Flowers. CRC Press, Boca Raton, FL. 176 pp.
Biswell, H. H. 1956. Ecology of California grasslands. J. Range Manage. 9:19-24.
Bowden, B. A. and G. Friesen. 1967. Competition of wild oats and flax. Weed Res. 7:349-359.
Budd, E. G. 1981. Survey, dormancy and life cycle of Bromus sterilis (sterile brome) in cereals, with particular reference to spring barley. J. Nat. Inst. Agric. Bot. 15:430-439.
Chouard, P. 1960. Vernalization and its relations to dormancy. Annu. Rev. Plant Physiol. 11:191-238.
Evans, L. T., ed. 1969. The Induction of Flowering: Some Case Histories. Cornell Univ. Press, New York. 488 pp.
Finnerty, D. W. and D. L. Klingman. 1962. Life cycles and control studies of some weed bromegrasses. Weeds. 10:40-47.
Fischer, B. B., A. H. Lange, and B. Crampton. 1983. rowers' weed identification handbook. Univ. Calif. Agric. Ext. Ser., Pub. 4030 WI 67.
Froud-Williams, R. J. 1983. The influence of straw disposal and cultivation regime on the population dynamics of Bromus sterilis. Ann. Appl. Biol. 103:139- 148. Froud-Williams, R. J., R. J. Chancellor, and D. S. H. Drennan. 1984. The effects of seed burial and soil disturbance on emergence and survival of arable weeds in relation to minimal cultivation. J. Appl. Ecol. 21:629-641.
Grabe, D. F. 1970. Tetrazolium Testing Handbook. Contribution 29 to the Handbook on Seed Testing, Association of Official Seed Analysts. 67
Harradine, A. R. 1986. Seed longevity and seedling establishment of Bromus diandrus Roth. Weed Res. 26:173-180. Hawkes, R. B., T. D. Whitson, and L. J. Dennis. 1985. A guide to selected weeds of Oregon. Oregon Dep. Agric., Oregon State Univ. Page 6.
Hitchcock, A. S. 1950. (Revised by A. Chase, 1971.) Manual of the grasses of the United States. 2nd. ed., Dover Publications, Inc., New York. Pages 52-53.
Hufstader, R. W. 1976. Precipitation, temperature, and the standing crop of some southern California grassland species. J. Range Manage. 29:433-435.
Hufstader, R. W. 1978. Growth rates and phenology of some southern California grassland species. J. Range Manage. 31:465-466.
Hulbert, L. C. 1955. Ecological studies of Bromus tectorum and other annual bromegrasses. Ecol. Monogr. 25:181- 213.
Hull, J. C. and C. H. Muller. 1976. Responses of California annual grassland species to variations in moisture and fertilization. J. Range Manage. 29:49-52.
Jain, S. K. 1982. Variation and adaptive role of seed dormancy in some annual grassland species. Bot. Gaz. 143:101-106.
Lang, A. 1965. Physiology of flower initiation. In W. Ruhland, ed. Encycl. Plant Physiol. 15:1380-1536.
Lyndon, R. F. 1977. Interacting processes in vegetative development and in the transition to flowering at the shoot apex. Pages 221-250 in D. H. Jennings, ed. Integration of Activity in the Higher Plant. Soc. Exp. Biol. Symp. 31. Cambridge Univ. Press, New York.
McGowan, A. A. 1970. Comparative germination patterns of annual grasses in north-eastern Victoria. Aust. J. Exp. Agric. Anim. Husb. 10:401-404.
Moore, R. J., ed. 1973. Index to plant chromosome numbers 1967-1971. International Bureau for Plant Taxonomy and Nomenclature, Utrecht, Netherlands. Pages 57-58.
Munz, P. A., and D. D. Keck. 1959. A California flora. FUniv. Calif. Press, Berkeley. 1681 pp.
Pollard, F. 1982. Light induced dormancy in Bromus sterilis. J. Appl. Ecol. 19:563-568. 68
Purvis, 0. N. 1966. The physiological analysis of vernalization. In W. Ruhland, ed. Encycl. Plant Physiol. 16:76-122.
Radosevich, S. R. and J. S. Holt. 1984. Weed Ecology: Implications for Vegetation Management. John Wiley & Sons, New York. Pages 106-110.
Schafer, D. E. and D. 0. Chilcote. 1969. Factors influencing persistence and depletion in buried seed populations. I. A model for analysis of parameters of buried seed persistence and depletion. Crop Sci. 9:417-418.
Silsbury, J. H. 1964. The effect of vernalization on the heading of Wimmera ryegrass (Lolium rigidum) and on five cultivars of perennial ryegrass (Lolium perenne). Aust. J. Exp. Agric. Anim. Husb. 4:352-356.
Smith, D. F. and G. R. T. Levick. 1974. The effect of infestation by Lolium rigidum on yield of wheat. Aust. J. Agric. Res. 25:381-393.
Thill, D. C., K. G. Beck, and R. H. Callihan. 1984. The biology of downy brome (Bromus tectorum). Weed Sci. 32:suppl. 1, 7-12.
Thurston, J. M. 1962. The effect of competition from cereal crops on the germination and growth of Avena fatua L. in a naturally infested field. Weed Res. 2:192-207.
Trione, E. J. and R. J. Metzger. 1970. Wheat and barley vernalization in a precise temperature gradient. Crop Sci. 10:390-392.
Vince-Prue, D. 1975. Photoperiodism in Plants. McGraw- Hill Book Co., New York. Pages 262-291.
Wicks, G. A. 1984. Integrated systems for control and management of downy brome (Bromus tectorum) in crop land. Weed Sci. 32:suppl. 1, 26-31.
Wicks, G. A., 0. C. Burnside, and C. R. Fenster. 1971. Influence of soil type and depth of planting on downy brome seed. Weed Sci. 19:82-86.
Young, J. A., R.A. Evans, and B. L. Kay. 1973. Temperaturerequirements for seed germination in an annual-typerangeland community. Agron. J. 65:656-659.
Young, J. A., R.A. Evans, and R. E. Eckert. 1969. Populationdynamics of downy brome. Weed Sci. 17:20- 26. APPENDIX 69
Appendix Table 1. Effect of ripgut brome density on winter wheat grain yield.
Wheat Ripgut seeding brome Grain yield rate density R1 R2 R3 R4 R5 Mean
(kg/ha) (plants/m2) (kg/ha)
56 0 8695 8016 8967 8559 6476 8142 105 6748 6612 7970 7744 7608 7336 340 5660 5344 6204 4800 5978 5597 665 5117 3668 5525 4212 3895 4483 1185 2762 3034 3125 3306 4076 3261
112 0 8650 8604 7155 8921 8604 8387 98 6883 8785 7155 8468 8016 7862 335 6295 8921 6340 8468 7699 7545 652 5072 7699 5253 8197 6748 6594 1175 3759 6883 3985 5117 6521 5253
168 0 7563 8106 8876 7789 8333 8133 90 6702 8423 8423 8333 7608 7898 326 6430 7427 7925 8604 6521 7382 646 7155 5978 8423 7834 5932 7065 1168 3487 5706 6657 6974 4166 5398
224 0 7699 9465 7563 9057 7970 8351 87 7699 8604 7291 8468 7517 7916 331 5389 4212 8514 7653 6657 6485 649 5751 7472 7472 7744 6159 6920 1152 3668 7699 6883 4347 5072 5534 70
Appendix Table 2. Analysis of variance table for effect of ripgut brome density on winter wheat grain yield.
Source of variation DF SS MS F P-value
Blocks 4 17380000 4344000
Wheat seeding rates 3 34440000 11480000 5.01 0.02
Error (a) 12 27520000 2294000
Ripgut brome levels 4 141300000 35320000 51.56 0.00
Interaction 12 18180000 1515000 2.21 0.02
Error (b) 64 43840000 685000
Total 99 282660000 71
Appendix Table 3. Effect of winter wheat seeding rate and ripgut brome density on total number of winter wheat shoots per unit area.
Wheat Ripgut seeding brome Total winter wheat shoots
rate density R1 R2 R3 R4 Mean
(kg/ha) (plants/m2) (Shoots/m2)
56 0 450 468 468 378 441 105 486 378 432 396 423 340 329 306 360 450 361 665 279 162 261 279 245 1185 59 117 180 378 184
112 0 617 414 675 495 550 98 531 567 360 495 488 335 360 342 513 504 430 652 225 423 342 495 371 1175 198 396 252 279 281
168 0 518 549 558 756 595 90 504 495 459 513 493 326 495 432 432 504 466 646 500 513 369 423 451 1168 261 477 342 324 351
224 0 603 558 594 540 574 87 576 495 549 459 520 331 477 621 450 495 511 649 522 639 486 405 513 1152 275 450 423 495 411 72
Appendix Table 4. Effect of ripgut brome density on total number of ripgut brome shoots per unit area.
Wheat Ripgut seeding brome Total ripgut brome shoots
rate density R1 R2 R3 R4 Mean
(kg/ha) (plants/m2) (Shoots/m2)
56 0 0 0 0 0 0 105 189 198 36 126 137 340 504 198 198 243 286 665 707 693 630 540 643 1185 774 855 657 810 774
112 0 0 0 0 0 0 98 192 603 63 36 224 335 513 216 540 180 362 652 684 351 558 270 466 1175 477 234 675 531 479
168 0 0 0 0 0 0 90 230 135 216 36 154 326 414 342 387 405 387 646 657 423 261 441 446 1168 531 486 441 657 529
224 0 0 0 0 0 0 87 153 99 108 135 124 331 297 180 234 351 266 649 387 234 414 387 356 1152 486 477 432 549 486 73
Appendix Table 5. Effect of winter wheat seeding rate and ripgut brome density on total winter wheat above-ground biomass.
Wheat Ripgut seeding brome Winter wheat above-ground shoots rate density R1 R2 R3 R4 Mean
(kg/ha) (plants/m2) (kg/ha)
56 0 20849 25371 26064 14589 21718 105 22091 20147 20178 16034 19612 340 16020 15170 16952 15926 16017 665 12546 8096 14652 13500 12198 1185 2664 5540 9113 18302 8904
0 22514 17901 27396 21348 22290 98 17625 24453 11228 23544 19212 335 15251 15318 20079 24030 18669 652 9360 20264 12992 21258 15968 1175 8906 18527 9851 12924 12552
168 0 21681 22176 25416 30294 24892 90 21528 22398 17501 24030 21364 326 19085 17292 18621 20394 18848 646 14090 24809 16826 19400 18781 1168 9405 18639 17168 13590 14700
224 0 224071 25506 25970 24786 25083 87 18057 20516 18608 17690 18717 331 16209 22703 16821 20250 18996 649 16371 22446 19463 15417 18424 1152 6908 15003 18779 17231 14480 74
Appendix Table 6. Effect of winter wheat seeding rate and ripgut brome density on total ripgut brome above-ground biomass.
Wheat Ripgut seeding brome Ripgut brome above-ground biomass rate density R1 R2 R3 R4 Mean
(kg/ha) (plants/m2) (kg/ha)
56 0 0 0 0 0 0 105 1845 2156 302 1206 1377 340 3956 2394 1413 2588 2588 665 4941 7997 4428 7146 6128 1185 7704 7704 3888 5783 6270
112 0 0 0 0 0 0 98 2277 689 473 716 1038 335 5927 1580 2444 2129 3020 652 5442 2147 3362 2439 3347 1175 9738 1625 3420 3785 4642
168 0 0 0 0 0 0 90 1620 1143 2003 279 1261 326 2786 2994 2786 4086 3163 646 4212 2817 1404 3294 2932 1168 5549 3456 1737 5355 4024
224 0 0 0 0 0 0 87 1752 995 707 1098 1138 331 2346 1805 1341 2412 1976 649 2478 1287 1994 2565 2081 1152 9162 2394 2030 3456 4260 75
Appendix Table 7. Effect of vernalization duration at 5 C on days to flowering, culms per plant,total shoot dry weight, total seed dry weight, and ratio of seed dry weight to shoot dry weight of ripgut brome after transfer tothe greenhouse. Year 1.
Duration of Time to Culms/ Shoot Seed Seed/ Block vernalization flowering plant weight weight shoot
(weeks) (days) (no.) (g) (g/g)
1 0 52 29 16.17 21.88 1.35 2 0 63 29 33.55 37.74 1.12 3 0 47 29 19.86 23.21 1.17 4 0 56 34 20.60 22.36 1.09 5 0 46 37 16.70 22.15 1.33 6 0 51 43 18.77 26.26 1.40 7 0 56 37 22.65 24.90 1.10 8 0 47 28 13.94 18.89 1.36 9 0 57 40 24.99 28.29 1.13 10 0 51 41 29.53 28.82 0.98 11 0 56 26 24.18 26.86 1.11 12 0 61 37 8.46 23.73 2.81 13 0 55 70 12.82 20.71 1.62 14 0 55 30 17.15 20.74 1.21 15 0 56 45 30.66 18.65 0.61 16 0 56 37 26.50 17.13 0.65 17 0 49 49 27.47 32.67 1.19 18 0 54 47 42.50 26.63 0.63 19 0 53 32 19.00 22.94 1.21 20 0 61 49 30.39 32.73 1.08 1 2 29 19 8.68 14.45 1.66 2 2 29 49 8.26 13.71 1.66 3 2 29 18 6.86 9.29 1.35 4 2 28 25 9.80 14.68 1.50 5 2 32 36 9.86 16.57 1.68 6 2 26 18 6.67 12.44 1.87 7 2 27 23 7.02 12.76 1.82 8 2 31 36 12.89 22.51 1.75 9 2 28 47 8.86 14.23 1.61 10 2 32 51 7.64 13.58 1.78 11 2 25 43 6.72 12.16 1.81 12 2 29 20 6.99 14.05 2.01 13 2 27 54 9.16 16.02 1.75 14 2 29 67 11.08 20.00 1.81 15 2 28 22 5.89 9.44 1.60 16 2 29 33 10.12 15.01 1.48 17 2 32 40 8.38 14.56 1.74 18 2 32 37 8.54 13.35 1.56 19 2 29 40 7.67 12.65 1.65 20 2 32 45 9.75 15.98 1.64 76
Appendix Table 7. (continued).
Duration of Time toCulms/ Shoot Seed Seed/ Block vernalization flowering plant weightweight shoot
(weeks) (days) (no.) (g) (g/g)
1 4 24 15 5.57 10.02 1.80 2 4 21 37 5.60 10.87 1.94 3 4 17 23 4.59 9.82 2.14 4 4 20 31 5.41 10.90 2.01 5 4 19 53 7.16 14.43 2.02 6 4 22 25 4.95 9.44 1.91 7 4 17 30 3.39 10.36 3.06 8 4 17 48 4.02 8.38 2.08 9 4 20 41 5.16 10.29 1.99 10 4 20 33 3.92 8.50 2.17 11 4 20 52 10.57 14.94 1.41 12 4 20 29 4.50 9.97 2.22 13 4 20 49 6.50 13.94 2.14 14 4 19 40 5.54 10.45 1.89 15 4 20 40 5.25 11.21 2.14 16 4 22 52 5.28 11.45 2.17 17 4 20 56 4.55 11.03 2.42 18 4 20 35 5.41 10.63 1.96 19 4 23 34 6.43 13.08 2.03 20 4 21 30 5.20 11.07 2.13 1 6 16 27 3.86 8.30 2.15 2 6 15 44 4.74 11.56 2.44 3 6 16 22 2.61 6.73 2.58 4 6 15 18 2.94 7.52 2.56 5 6 15 36 3.82 9.29 2.43 6 6 14 26 3.90 9.10 2.33 7 6 15 40 3.47 8.32 2.40 8 6 15 37 3.72 11.29 3.03 9 6 14 28 3.69 8.12 2.20 10 6 15 27 3.03 9.45 3.12 11 6 17 48 3.71 8.04 2.17 12 6 15 44 3.86 9.54 2.47 13 6 15 27 2.69 6.89 2.56 14 6 15 37 3.02 7.49 2.48 15 6 15 25 3.85 9.91 2.57 16 6 15 30 4.28 9.59 2.24 17 6 14 38 3.75 9.90 2.64 18 6 15 42 4.84 13.31 2.75 19 6 17 34 2.92 8.24 2.82 20 6 19 38 3.97 11.14 2.81 77
Appendix Table 7. (continued).
Duration of Time to Culms/ Shoot Seed Seed/ Block vernalization flowering plant weightweight shoot
(weeks) (days) (no.) (g) (g/g)
1 8 15 33 2.70 6.71 2.49 2 8 14 27 3.01 7.81 2.59 3 8 15 27 3.27 8.08 2.47 4 8 14 16 1.87 4.05 2.17 5 8 16 44 4.45 9.54 2.14 6 8 15 16 2.94 7.12 2.42 7 8 17 31 3.98 9.34 2.35 8 8 14 44 3.58 9.94 2.78 9 8 15 36 3.37 7.32 2.17 10 8 15 27 2.95 7.45 2.53 11 8 16 38 3.11 7.68 2.47 12 8 15 36 2.70 6.67 2.47 13 8 15 38 2.82 7.17 2.54 14 8 15 36 3.01 7.66 2.54 15 8 14 34 3.44 8.06 2.34 16 8 14 45 3.56 9.73 2.73 17 8 15 41 3.77 9.54 2.53 18 8 14 34 3.73 9.06 2.43 19 8 15 34 4.34 11.88 2.74 20 8 17 34 3.24 9.25 2.85 78
Appendix Table 8. Effect of vernalization duration at 5 C on days to flowering, culms per plant, total shoot dry weight, total seed dry weight, and ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhouse. Year 2.
Duration of Time to Culms/ Shoot Seed Seed/ Block vernalization flowering plant weight weight shoot
(weeks) (days) (no.) (g) (g/g)
1 0 46 20 6.66 13.90 2.09 2 0 58 34 17.24 20.83 1.21 3 0 57 38 25.09 25.52 1.02 4 0 48 28 13.62 16.89 1.24 5 0 50 36 21.16 20.25 0.96 6 0 51 33 22.71 18.30 0.81 7 0 46 30 13.79 15.72 1.14 8 0 51 34 15.05 17.52 1.16 9 0 57 36 20.08 22.73 1.13 10 0 54 20 11.75 16.34 1.39 11 0 51 31 24.69 32.41 1.31 12 0 53 18 36.74 17.03 0.46 13 0 52 14 10.28 10.24 0.00 14 0 56 25 8.84 14.63 1.65 15 0 51 54 18.60 19.93 1.07 16 0 49 38 14.27 29.20 2.05 17 0 50 59 29.52 32.49 1.10 18 0 52 28 29.59 15.79 0.53 19 0 51 53 20.23 25.10 1.24 20 0 48 19 12.17 13.73 1.13 1 2 27 17 0.99 3.15 3.19 2 2 26 28 2.52 7.01 2.79 3 2 29 23 6.02 12.20 2.03 4 2 29 32 9.60 15.62 1.63 5 2 37 26 8.39 12.15 1.45 6 2 34 34 8.36 13.85 1.66 7 2 29 24 9.71 11.94 1.23 8 2 29 14 6.29 9.14 1.45 9 2 29 30 2.64 5.86 2.22 10 2 29 51 7.77 16.92 2.18 11 2 29 13 3.71 7.34 1.98 12 2 29 18 0.76 2.41 3.16 13 2 29 42 6.08 14.19 2.34 14 2 28 15 1.64 4.58 2.80 15 2 29 30 3.23 8.22 2.54 16 2 28 25 5.28 14.92 2.83 17 2 26 21 2.68 10.35 3.86 18 2 29 35 4.96 11.18 2.25 19 2 25 50 5.88 12.75 2.17 20 2 30 31 7.16 13.24 1.85 79
Appendix Table 8. (continued).
Duration of Time to Culms/ Shoot Seed Seed/ Block vernalization flowering plant weightweight shoot
(weeks) (days) (no.) (g) (g/g)
1 4 26 27 1.77 5.86 3.32 2 4 23 21 1.68 3.88 2.31 3 4 23 32 3.60 8.70 2.41 4 4 23 25 3.72 8.54 2.30 5 4 23 37 5.02 11.63 2.32 6 4 23 24 2.78 6.69 2.40 7 4 26 23 3.96 9.47 2.39 8 4 23 43 3.86 10.17 2.64 9 4 23 17 1.97 4.84 2.46 10 4 23 20 2.71 7.11 2.62 11 4 18 18 3.01 8.03 2.67 12 4 25 21 1.16 4.06 3.50 13 4 21 25 1.86 6.05 3.26 14 4 22 9 0.85 2.16 2.54 15 4 23 24 2.61 6.55 2.50 16 4 24 13 2.50 5.20 2.08 17 4 23 18 1.74 5.33 3.07 18 4 20 17 4.81 9.00 1.87 19 4 26 22 3.67 10.25 2.79 20 4 22 20 2.17 6.65 3.07 1 6 21 7 0.82 2.70 3.29 2 6 21 19 1.41 4.21 2.99 3 6 19 14 2.85 7.64 2.68 4 6 20 18 1.98 6.52 3.29 5 6 20 8 1.30 3.79 2.92 6 6 23 21 2.09 6.64 3.18 7 6 21 8 1.91 4.36 2.29 8 6 19 7 1.43 3.73 2.62 9 6 21 31 4.00 8.75 2.92 10 6 20 26 1.82 5.68 3.13 11 6 20 10 1.15 3.09 2.69 12 6 20- 12 0.00 3.05 3.07 13 6 20 19 0.68 4.25 6.21 14 6 20 9 0.42 1.48 3.53 15 6 20 27 1.60 4.04 2.53 16 6 19 35 2.91 8.45 2.90 17 6 20 10 2.36 6.18 2.62 18 6 20 17 1.20 2.91 2.44 19 6 22 17 2.36 6.81 2.88 20 6 20 19 1.56 5.52 3.54 80
Appendix Table 8. (continued).
Duration of Time to Culms/ Shoot Seed Seed/ Block vernalization flowering plant weight weight shoot
(weeks) (days) (no.) (g) (g/g)
1 8 18 21 1.49 4.83 3.24 2 8 15 23 1.16 6.26 5.42 3 8 19 30 2.61 7.30 2.80 4 8 19 29 3.36 8.46 2.52 5 8 19 35 1.87 6.14 3.28 6 8 18 34 2.73 7.58 2.77 7 8 19 20 2.28 5.89 2.59 8 8 18 36 1.72 7.42 4.32 9 8 19 13 1.18 4.78 4.05 10 8 19 21 1.73 5.56 3.22 11 8 19 36 2.33 7.27 3.12 12 8 20 10 1.05 2.66 2.54 13 8 19 20 1.26 3.96 3.14 14 8 19 27 1.57 4.84 3.09 15 8 18 43 2.26 8.77 3.89 16 8 18 24 1.59 4.75 2.99 17 8 18 35 2.82 7.87 2.79 18 8 19 15 1.90 3.83 2.01 19 8 18 11 1.14 3.94 3.45 20 8 18 19 2.00 6.50 3.24 81
Appendix Table 9. Analysis of variance table for effect of vernalization duration at 5 C on days to flowering of ripgut brome after transfer to the greenhouse.
Source of variation DF SS MS F P-value
Blocks 39 349 8.90
Treatments 4 35560 8889.00 115.00 0.00
Error 156 1243 7.97
Total 199 37152
Appendix Table 10. Analysis of variance table for effect of vernalization duration at 5 C on culms per plant of ripgut brome after transfer to the greenhouse.
Source of variation DF SS MS F P-value
Blocks 39 12580 322.60
Treatments 4 2311 577.80 6.47 0.00
Error 156 13940 89.38
Total 199 28831 82
Appendix Table 11. Analysis of variance table for effect of vernalization duration at 5 C on total shoot dry weight of ripgut brome after transfer to the greenhouse.
Source of variation DF SS MS F P-value
Blocks 39 932 23.91
Treatments 4 9339 2335.00 165.80 0.00
Error 156 2196 14.08
Total 199 12467
Appendix Table 12. Analysis of variance table for effect of vernalization duration at 5 C on total seed dry weight per plant of ripgut brome after transfer to the greenhouse.
Source of variation DF SS MS F P-value
Blocks 39 1374 35.23
Treatments 4 6587 1647.00 159.70 0.00
Error 156 1609 10.31
Total 199 9570 83
Appendix Table 13. Analysis of variance table for effect of vernalization duration at 5 C on ratio of seed dry weight to shoot dry weight of ripgut brume after transfer to the greenhouse.
Source of variation DF SS MS F P-value
Blocks 39 25 0.64
Treatments 4 75 18.74 80.09 0.00
Error 156 37 0.23
Total 199 137 84
Appendix Table 14. Effect of outdoor cold treatment on days to flowering, culms per plant, total shoot dry weight, total seed dry weight, and ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhouse. Year 1.
Duration of Time to Culms/ Shoot Seed Seed/ Block vernalization flowering plant weight weight shoot
(weeks) (days) (no.) (g) (g/g)
1 0 52 38 36.60 28.59 0.78 2 0 63 25 30.11 11.60 0.39 3 0 47 30 39.37 15.11 0.38 4 0 56 52 55.36 36.95 0.67 5 0 46 34 33.36 8.34 0.25 6 0 51 38 23.57 17.04 0.72 7 0 56 65 23.71 26.71 1.13 8 0 47 28 47.38 15.36 0.32 9 0 57 44 48.48 20.64 0.43 10 0 51 44 36.88 13.61 0.37 11 0 56 53 47.58 21.82 0.46 12 0 61 51 38.21 21.30 0.56 13 0 55 42 21.69 18.04 0.83 14 0 55 24 49.61 3.68 0.07 15 0 56 36 21.79 23.11 1.06 16 0 56 28 27.39 15.29 0.56 17 0 49 25 22.22 9.67 0.44 18 0 54 24 21.63 8.74 0.40 19 0 53 26 30.60 5.98 0.20 20 0 61 53 44.67 19.25 0.43 1 4 11 31 9.54 11.54 1.21 2 4 14 43 5.07 14.30 2.82 3 4 9 31 5.07 11.54 2.28 4 4 12 30 5.12 11.65 2.28 5 4 9 36 6.13 11.19 1.83 6 4 12 27 4.37 13.14 3.01 7 4 9 45 8.14 16.58 2.04 8 4 12 30 6.16 13.21 2.14 9 4 15 39 5.69 13.81 2.43 10 4 15 39 6.07 12.88 2.12 11 4 9 28 5.28 9.33 1.77 12 4 9 20 3.26 8.40 2.58 13 4 12 24 3.99 14.89 3.73 14 4 11 26 4.10 9.26 2.26 15 4 11 23 3.48 7.09 2.04 16 4 14 19 3.11 7.26 2.33 17 4 11 31 5.07 11.54 2.28 18 4 9 12 1.19 11.54 9.70 19 4 14 48 5.82 14.09 2.42 20 4 12 41 4.78 7.50 1.57 85
Appendix Table 14. (continued).
Duration of Time to Culms/ Shoot Seed Seed/ Block vernalization flowering plant weightweight shoot
(weeks) (days) (no.) (g) (g/g)
1 8 34 6 4.93 14.95 3.03 2 8 36 8 2.92 8.97 3.07 3 8 32 17 5.20 14.75 2.84 4 8 34 11 4.14 13.39 3.23 5 8 34 10 3.50 10.96 3.13 6 8 34 8 3.28 10.59 3.23 7 8 31 10 3.21 8.91 2.78 8 8 33 18 7.14 17.67 2.47 9 8 33 7 2.68 7.79 2.91 10 8 25 13 6.54 15.51 2.37 11 8 29 11 3.39 8.86 2.61 12 8 31 8 2.70 7.28 2.70 13 8 29 6 1.08 2.37 2.19 14 8 30 7 0.82 1.67 2.04 15 8 31 6 1.01 3.87 3.83 16 8 29 9 1.91 4.89 2.56 17 8 29 15 2.55 7.21 2.83 18 8 28 9 2.70 7.11 2.63 19 8 29 12 1.98 5.88 2.97 20 8 29 12 2.46 5.48 2.23 1 12 31 21 2.30 6.67 2.90 2 12 31 9 3.94 6.67 1.69 3 12 31 23 5.37 11.97 2.23 4 12 31 10 2.59 7.41 2.86 5 12 31 26 2.92 6.68 2.29 6 12 31 26 2.78 4.76 1.71 7 12 31 35 3.80 10.47 2.76 8 12 31 26 2.41 7.20 2.99 9 12 29 29 2.62 7.99 3.05 10 12 29 36 3.65 10.44 2.86 11 12 30 31 3.13 7.89 2.52 12 12 30 15 2.34 4.81 2.06 13 12 29 21 2.78 6.67 2.40 14 12 27 10 2.78 3.43 1.23 15 12 29 14 1.58 3.81 2.41 16 12 27 17 3.49 8.38 2.40 17 12 29 13 1.07 3.01 2.81 18 12 35 25 3.13 8.66 2.77 19 12 29 15 1.08 2.88 2.67 20 12 31 19 1.88 3.65 1.94 86
Appendix Table 14. (continued).
Duration of Time toCulms/ Shoot Seed Seed/ Block vernalization flowering plant weightweight shoot
(weeks) (days) (no.) (g) (g/g)
1 16 27 11 1.26 4.17 3.31 2 16 27 17 2.61 3.31 1.27 3 16 27 27 1.77 6.76 3.82 4 16 26 27 3.70 7.90 2.14 5 16 26 24 3.03 6.78 2.24 6 16 27 15 1.60 3.59 2.24 7 16 27 28 4.03 8.12 2.01 8 16 26 33 2.29 6.27 2.74 9 16 26 19 1.96 4.02 2.05 10 16 26 30 3.45 8.90 2.58 11 16 26 9 1.43 2.43 1.70 12 16 27 10 1.33 2.71 2.04 13 16 25 16 2.99 6.44 2.15 14 16 26 11 7.32 2.97 0.41 15 16 26 19 8.00 7.29 2.43 16 16 27 10 1.04 1.18 1.13 17 16 26 12 1.82 3.92 2.15 18 16 26 22 3.10 6.16 1.99 19 16 27 17 1.87 4.17 2.23 20 16 27 27 2.69 6.23 2.32 1 20 23 34 2.76 13.37 4.84 2 20 22 40 3.62 14.21 3.93 3 20 23 55 4.60 8.46 1.84 4 20 23 18 3.12 6.76 2.17 5 20 23 24 2.28 4.33 1.90 6 20 23 16 2.91 4.95 1.70 7 20 22 29 4.43 8.85 4.00 8 20 22 15 2.94 5.98 2.03 9 20 22 36 4.85 7.36 1.52 10 20 21 24 4.71 10.07 2.14 11 20 23 24 3.90 6.85 1.76 12 20 21 15 3.50 66.53 19.01 13 20 22 24 4.40 6.59 1.50 14 20 21 18 3.41 2.41 0.71 15 20 23 16 2.43 4.11 1.69 16 20 22 17 1.34 3.74 2.79 17 20 21 18 2.53 4.16 1.64 18 20 23 22 3.56 6.52 1.83 19 20 23 26 2.35 3.81 1.62 20 20 21 32 4.55 9.32 2.05 87
Appendix Table 14. (continued).
Duration of Time to Culms/ Shoot Seed Seed/ Block vernalization flowering plant weightweight shoot
(weeks) (days) (no.) (g) (g/g)
1 24 8 20 3.39 8.68 2.56 2 24 8 17 4.22 8.51 2.02 3 24 8 14 2.96 8.72 2.94 4 24 9 26 2.64 4.85 1.84 5 24 9 35 3.32 6.70 2.02 6 24 0 25 2.77 4.75 1.71 7 24 9 22 2.79 5.47 1.96 8 24 9 15 3.71 24.00 1.89 9 24 9 29 3.65 6.77 1.85 10 24 8 23 3.63 7.09 1.95 11 24 8 23 3.63 7.09 1.95 12 24 9 32 5.70 11.71 2.05 13 24 10 27 3.69 6.76 1.83 14 24 10 15 3.24 5.49 1.69 15 24 7 15 6.64 12.06 1.82 16 24 9 7 2.48 5.26 2.12 17 24 9 15 4.11 8.42 2.05 18 24 9 24 3.18 4.90 1.54 19 24 9 34 2.91 5.27 1.81 20 24 11 34 3.96 6.36 1.61 1 30 0 47 5.81 23.15 3.98 2 30 0 21 7.03 13.53 1.92 3 30 0 18 8.37 15.57 1.86 4 30 0 18 11.78 19.15 1.63 5 30 0 25 3.91 20.15 5.15 6 30 0 20 5.22 21.26 4.07 7 30 0 10 7.03 6.50 0.92 8 30 0 45 12.19 19.30 1.58 9 30 0 11 3.37 4.41 1.31 10 30 0 16 6.59 11.13 1.69 11 30 0 17 6.13 9.99 1.63 12 30 0 27 8.84 15.49 1.75 13 30 0 13 20.00 9.69 1.62 14 30 0 37 4.81 10.07 2.09 15 30 0 15 7.23 11.40 1.58 16 30 0 18 8.95 12.12 1.35 17 30 0 10 5.67 8.74 1.54 18 30 0 14 5.86 10.34 1.76 19 30 0 14 5.23 9.39 1.80 20 30 0 29 10.52 19.18 1.82 88
Appendix Table 15. Effect of outdoor cold treatment on days to flowering, culms per plant, total shoot dry weight, total seed dry weight, and ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhouse. Year 2.
Duration of Time to Culms/ Shoot Seed Seed/ Block vernalization flowering plant weightweight shoot
(weeks) (days) (no.) (g) (g/g)
1 0 77 37 21.87 13.25 0.61 2 0 80 51 24.08 29.49 1.22 3 0 86 56 29.28 29.47 1.01 4 0 99 67 35.75 36.67 1.03 5 0 78 56 35.68 32.85 0.92 6 0 74 50 19.89 24.51 1.23 7 0 79 47 27.72 28.06 1.01 8 0 70 57 15.38 22.15 1.44 9 0 77 61 38.04 29.73 0.78 10 0 68 87 16.11 11.41 0.71 11 0 78 42 32.94 29.06 0.88 12 0 77 74 32.15 35.83 1.11 13 0 77 48 52.36 14.41 0.28 14 0 78 36 19.52 9.24 0.47 15 0 77 70 39.52 29.97 0.76 16 0 78 22 23.95 11.22 0.47 17 0 78 60 38.17 28.11 0.74 18 0 71 69 30.68 34.99 1.14 19 0 77 52 34.39 25.34 0.74 20 0 73 69 34.02 29.55 0.87 1 4 45 24 1.85 5.56 3.01 2 4 45 31 4.17 9.90 2.37 3 4 45 27 2.74 10.84 3.96 4 4 45 25 3.56 10.06 2.83 5 4 45 21 3.44 9.44 2.74 6 4 45 20 5.26 10.14 1.93 7 4 45 13 4.26 8.21 1.93 8 4 45 15 4.28 8.15 1.90 9 4 45 50 7.55 15.03 1.99 10 4 45 11 3.32 7.82 2.36 11 4 45 78 4.60 9.17 1.99 12 4 45 28 5.78 13.65 2.36 13 4 45 31 7.68 14.89 1.94 14 4 45 20 4.01 15.54 3.88 15 4 45 21 4.59 11.54 2.51 16 4 45 30 5.53 11.59 2.10 17 4 42 21 6.54 12.99 1.99 18 4 47 38 6.76 12.84 1.90 19 4 45 20 4.42 10.49 2.37 20 4 46 10 8.92 8.92 0.00 89
Appendix Table 15. (continued).
Duration of Time to Culms/ Shoot Seed Seed/ Block vernalization flowering plant weightweight shoot
(weeks) (days) (no.) (g) (g/g)
1 8 33 22 4.14 9.36 2.26 2 8 32 19 7.93 8.42 1.06 3 8 32 26 5.12 12.78 2.50 4 8 32 50 5.71 13.83 2.42 5 8 33 38 3.67 12.65 3.45 6 8 33 23 3.99 10.09 2.53 7 8 32 29 5.80 13.35 2.30 8 8 33 30 6.57 12.08 1.84 9 8 32 59 4.92 18.46 3.75 10 8 32 31 4.62 11.73 2.54 11 8 33 51 7.25 17.43 2.40 12 8 33 35 7.30 16.30 2.23 13 8 33 38 5.50 14.03 2.55 14 8 32 42 5.12 13.52 2.64 15 8 32 37 5.81 14.37 2.47 16 8 33 35 7.25 16.04 2.21 17 8 33 49 6.46 16.40 2.54 18 8 31 52 7.26 17.84 2.46 19 8 32 50 6.10 16.09 2.64 20 8 33 53 5.91 15.83 2.68 1 12 27 17 4.96 10.18 2.05 2 12 27 13 2.88 6.80 2.36 3 12 26 18 4.45 9.11 2.05 4 12 25 19 5.32 9.98 1.88 5 12 27 17 5.34 11.73 2.20 6 12 25 24 4.66 11.50 2.47 7 12 25 22 5.35 10.64 1.99 8 12 26 19 4.79 10.24 2.14 9 12 26 37 5.17 13.82 2.67 10 12 25 10 2.52 5.19 2.06 11 12 26 20 4.69 8.97 1.91 12 12 26 19 5.76 11.91 2.07 13 12 26 27 5.05 14.95 2.96 14 12 26 11 6.02 7.39 1.23 15 12 25 21 3.80 9.34 2.46 16 12 26 21 5.49 11.08 2.02 17 12 25 23 6.59 12.72 1.93 18 12 26 23 5.11 9.71 1.90 19 12 26 16 4.36 8.70 4.00 20 12 25 28 4.39 10.74 2.45 90
Appendix Table 15. (continued).
Duration of Time to Culms/ Shoot Seed Seed/ Block vernalization flowering plant weightweight shoot
(weeks) (days) (no.) (g) (g/g)
1 16 18 12 7.01 8.76 1.25 2 16 19 40 8.60 12.47 1.45 3 16 19 12 4.83 7.45 1.54 4 16 19 14 7.77 9.89 1.27 5 16 18 41 8.56 14.21 1.66 6 16 18 28 6.24 8.69 1.39 7 16 19 14 9.17 12.59 1.37 8 16 18 13 7.11 8.94 1.26 9 16 18 22 8.79 11.50 1.31 10 16 18 8 4.97 7.49 1.51 11 16 19 13 7.48 9.52 1.27 12 16 18 68 10.05 17.10 1.70 13 16 19 25 5.40 8.41 1.56 14 16 19 54 7.47 12.93 1.73 15 16 19 20 8.45 11.36 1.34 16 16 18 25 8.29 10.64 1.28 17 16 18 15 7.39 11.23 1.52 18 16 18 19 6.92 9.47 1.37 19 16 19 21 5.89 10.09 1.71 20 16 18 13 7.73 11.39 1.47 1 20 23 13 6.94 8.20 1.18 2 20 22 12 9.58 11.96 1.25 3 20 23 19 6.68 8.95 1.34 4 20 23 25 8.84 11.20 1.27 5 20 23 13 8.80 10.38 1.18 6 20 23 14 7.30 9.07 1.24 7 20 22 45 6.83 11.34 1.66 8 20 22 16 10.53 12.37 1.17 9 20 22 42 13.14 16.65 1.27 10 20 21 12 5.06 7.61 1.50 11 20 23 19 7.93 10.61 1.34 12 20 21 12 7.54 10.22 1.36 13 20 22 17 8.35 10.15 1.22 14 20 21 11 5.41 6.83 1.26 15 20 23 12 6.86 9.45 1.38 16 20 22 11 5.75 6.33 1.10 17 20 21 32 4.94 7.43 1.50 18 20 23 39 8.20 10.82 1.32 19 20 23 13 8.47 8.48 0.00 20 20 21 30 5.70 11.43 2.01 91
Appendix Table 15. (continued).
Duration of Time to Culms/ Shoot Seed Seed/ Block vernalization flowering plant weightweight shoot
(weeks) (days) (no.) (g) (g/g)
1 24 8 9 6.66 7.51 1.13 2 24 8 11 8.50 10.83 1.27 3 24 8 17 7.96 9.36 1.18 4 24 9 14 8.56 11.56 1.35 5 24 9 13 9.83 11.85 1.21 6 24 0 14 8.64 10.56 1.22 7 24 9 13 7.92 9.85 1.24 8 24 9 16 11.48 14.23 1.24 9 24 9 13 10.99 11.29 1.03 10 24 8 15 10.24 13.15 1.28 11 24 8 15 10.58 13.60 1.29 12 24 9 15 9.13 11.12 1.22 13 24 10 13 9.46 12.20 1.29 14 24 10 15 10.96 11.45 1.04 15 24 7 14 9.75 10.21 1.05 16 24 9 12 8.42 10.14 1.20 17 24 9 17 9.87 14.58 1.48 18 24 9 15 10.22 15.12 1.48 19 24 9 18 12.17 16.22 1.33 20 24 11 13 11.78 14.31 1.21 1 30 0 13 12.91 18.96 1.47 2 30 0 16 13.43 18.47 1.38 3 30 0 11 17.26 29.33 1.70 4 30 0 19 16.55 24.81 1.50 5 30 0 14 10.80 17.12 1.59 6 30 0 16 15.23 24.22 1.59 7 30 0 18 13.99 25.30 1.81 8 30 0 12 12.75 11.73 0.92 9 30 0 19 11.84 26.33 2.22 10 30 0 15 13.24 22.39 1.69 11 30 0 18 13.32 20.81 1.56 12 30 0 14 15.39 24.09 1.57 13 30 0 25 19.32 32.89 1.70 14 30 0 15 15.26 22.67 1.49 15 30 0 16 15.72 23.64 1.50 16 30 0 14 12.16 16.39 1.35 17 30 0 15 13.98 19.86 1.42 18 30 0 18 17.18 28.97 1.69 19 30 0 19 17.50 26.65 1.52 20 30 0 22 17.26 29.33 1.70 92
Appendix Table 16. Analysis of variance table for effect of outdoor cold treatment on days to flowering of ripgut brome after transfer to the greenhouse.
Source of variation DF SS MS F P-value
Blocks 39 2899 74.34
Treatments 7 105700 15100.00 251.40 0.00
Error 273 16400 60.06
Total 319 124999
Appendix Table 17. Analysis of variance table for effect of outdoor cold treatment on cuims per plant of ripgut brome after transfer to the greenhouse.
Source of variation DF SS MS F P-value
Blocks 39 7218 185.10
Treatments 7 24310 3473.00 25.38 0.00
Error 273 37350 136.80
Total 319 68878 93
Appendix Table 18. Analysis of variance table for effect of outdoor cold treatment on total shoot dry weight of ripgut brome after transfer to the greenhouse.
Source of variation DF SS MS F P-value
Blocks .39 1482 38.01
Treatments 7 26150 3736.00 211.40 0.00
Error. 273 4824 17.67
Total 319 32456
Appendix Table 19. Analysis of variance table for effect of outdoor cold treatment on total seed dry weight of ripgut brome after transfer to the greenhouse.
Source of variation DF SS MS F P-value
Blocks 39 3565 91.41
Treatments 7 6565 937.90 32.79 0.00
Error 273 7809 28.60
Total 319 17939 94
Appendix Table 20. Analysis of variance table for effect of outdoor cold treatment on ratio of seed dry weight to shoot dry weight of ripgut brome after transfer to the greenhouse.
Source of variation DF SS MS F P-value
Blocks 39 71 1.81
Treatments 7 106 15.07 10.82 0.00
Error 273 380 1.39
Total 319 557