Annual ryegrass ( Lolium multiflourum) is the most important cool-season forage crop in Mississippi. It is seeded on more than 500,000 acres every year in the state and consequently seed companies intensely market the area with claims of superior genetic performance. Marketing literature observed in Mississippi focuses on the performance of tetraploid (4×) versus diploid (2×) with claims that 4× varieties provide better yield, disease resistance, and seedling vigor. These claims have rarely been substantiated on long-term performance variety trials. Archived Mississippi State forage variety test data from 1987 to 2012 were compiled for 10 diploid and tetraploid varieties grown at four physiographic locations (Starkville, Raymond, Newton, and Poplarville). Differences in the mean yields between 2× and 4× were only detected in Newton and Poplarville, where 2× varieties had a 4% yield advantage and 4× averaged 10% greater yields, respectively. Across the state, ryegrass yields for both ploidy levels increased over time (4×, R = 0.19931, P = 0.0105 & 2×, R = 0.18816, P = 0.0003), but correlations were variable by location. Biomass yields for both ploidy levels decreased over time in Starkville despite an increase in GDD (Growing Degree Days). With the exception of Raymond, year was the only factor influencing yield. The data suggest that ploidy level of ryegrass in Mississippi has minimal impact on seasonal yield production. However, genetic improvement other than polyploidy induction has increased yield over time.
Annual ryegrass (Lolium multiflorum) is the most important cool-season forage crop in Mississippi. Ryegrass is established on more than 500,000 acres every year in the state primarily for grazing cattle (especially stocker) or making hay or baleage. It is a C3 annual crop that is usually overseeded in the fall (September to October) into a warm-season grass sod and utilized on prepared seedbed as early as December in south Mississippi to as late as April in the northern part of the state. Varieties of ryegrass are generally divided into two ploidy types: diploids (2×) and tetraploids (4×). Until 1985, annual ryegrass varieties were only diploids. Tetraploids were first pro- duced by treating germinating seeds with colchicine and selecting for plants with doubled chromosomes [
Tetraploids usually have wider leaves and an overall larger plant along with better disease resistance to crown rust (Puccinia coronate) [
Marshall is the most widely planted variety in Mississippi despite new commercial varieties being made available. This diploid variety released in 1981 by Mississippi State University is estimated to make up 60% of the ryegrass acreage in the state [
Yield data from the Mississippi State forage variety trials was analyzed from 1987-2012 [
Correlation analysis was accomplished using the PROC CORR option of SAS (SAS Institute Inc., Cary, NC) to observe significant negative or positive correlations (P = 0.05). Significant correlation data was then charac- terized using a linear regression model. Average yields were analyzed for both test to report overall performance of ploidy, location, variety, variety × location, and ploidy × location using years as reps for each variety. The statistical analysis of yield performance was done using PROC GLM option of SAS and means separated using the least significant difference (LSD) when α = 0.05 or 0.10 when otherwise noted.
The forage variety testing program has utilized several locations over the years, but only data from Starkville (Henry H. Leveck Animal Research Farm), Newton (Coast Plain Experiment Station), Poplarville (White Sands Research Unit), and Raymond (Brown Loam Branch Station) was utilized for this report. The locations were chosen simply due to the amount of variety testing data that has been recorded for ryegrass at these locations
Ploidy | Variety | N = Environments (Years) | Maturity | Cold Tolerance |
---|---|---|---|---|
Diploid | ||||
Brigadier | 16 | Early | High | |
Bulldog Grazer | 20 | Early-Late | Medium-High | |
Gulf | 51 | Early-Mid | Low-Medium | |
Jackson | 59 | Mid-Late | High | |
King | 15 | Medium | Medium | |
Lonestar | 10 | Early | High | |
Marshall | 68 | Late | High | |
Passerel Plus | 33 | Late | High | |
Rio | 42 | Mid-Late | High | |
TAM90 | 48 | Mid-Late | Medium-High | |
Tetraploid | ||||
Big Daddy | 14 | Mid-Late | Medium | |
Diamond T | 14 | Medium | Medium-High | |
Hercules | 13 | Medium | High | |
Hurricane | 9 | NA† | NA | |
Jumbo | 29 | Late | Medium-High | |
Maximus | 14 | Medium | Medium-High | |
Multimo | 23 | NA | NA | |
Prine | 26 | Late | High | |
Tetragold | 13 | NA | NA | |
Verdue | 9 | NA | NA |
†NA = Not available.
(
For this report yields were assumed to not be affected by differing management strategies and fertilizer regi- ments that characterized the variety trials over the 25-year period. This variability was expected to be minimized across independent variables because of increased replications (years). Typically the number of replications or environments of which data points were derived was less with tetraploid varieties than diploid due to the rela- tively recent formation and adoption of tetraploid varieties.
The main effects of variety (P = 0.0018) and location (P = 0.0001) using years as replications was found to have significance. Specifically, varieties were found to interact according to location (P = 0.0008). When varieties were grouped by ploidy level no difference was found in means pooled across all locations. However, an inte- raction of location by ploidy level did exist when significance was considered at P = 0.10. Weather ryegrass was considered, by variety or ploidy level, harvest years (replications) were different (P = 0.0001). Across Missis-
sippi, ryegrass yields for both types increased over time (4×, R = 0.19931, P = 0.0105 & 2×, R = 0.18816, P = 0.0003), but correlations were variable by location. Growing degree days did not increase as years increased with the exception of Starkville (
Differences between tetraploid and diploid ryegrass yields could not be detected at any location except Newton and Poplarville. Diploids at Newton averaged yields 4% greater than tetraploids. Alternatively, tetraploids in Poplarville had a greater advantage over diploids with a 10% increase in yield. A positive yield correlation did exist for both tetraploids (R = 0.19931, P2 = 0.0105) and diploids (R = 0.18816, P = 0.0003) as years increased. A regression model presented similar yield trends for diploids (
In Mississippi, variety test performance data did not suggest an advantage in tetraploid over diploid biomass production. The only location could present a yield advantage from tetraploid ryegrass might be Poplarville (Southernmost location) where less cold temperatures could negatively impact growth. The results are consistent with previous research where tetraploids have shown greatest yields in Texas and Louisiana near the coast line [
Location | |||||
---|---|---|---|---|---|
Poplarville | Newton | Raymond | Starkville | ||
Rainfall | Pvalue | 0.0001 | 0.0110 | 0.0069 | 0.8599 |
Rvalue | −0.5020 | −0.1803 | 0.2529 | −0.0196 | |
GDD | Pvalue | 0.0001 | 0.0479 | 0.2824 | 0.0001 |
Rvalue | −0.4890 | 0.1407 | 0.1019 | 0.5680 |
suggest that when temperatures are too warm in the spring we can actually expect lower total annual yields to an accelerated shutdown of plant physiological processes. This could be due to many factors including an increase in the rate of maturity by plants equivalent to less vegetative re-growth after harvest and increase in day length.
Polyploidy induction of ryegrass only promises increased advantages in very specific locations, evaluating by variety may be the most effective strategy towards proper recommendations in Mississippi.
Varieties were greatly affected by location as presented in
Location | |||||||||
---|---|---|---|---|---|---|---|---|---|
Variety | Ploidy | Poplarville | Newton | Raymond | Starkville | Mean | LSD0.05 | CV% | |
kg∙ha−1 | |||||||||
Big Daddy | 4× | 7681 | 6608 | 7767 | 9246 | 7826 | NS | 12.8 | |
Brigadier | 2× | 4448 | 6907 | 10086 | 7980 | 7355 | 1921 | 17.8 | |
Bulldog Grazer | 2× | 5567 | 7762 | 8223 | 7136 | 7172 | NS | 22.7 | |
Diamond T | 4× | 6033 | 8110 | . | 8488 | 7544 | NS | 22.3 | |
Gulf | 2× | 5461 | 7038 | 7166 | 8461 | 7032 | 1394 | 29.1 | |
Hercules | 4× | 7465 | 7169 | 6035 | 11,212 | 7970 | 1629 | 13.2 | |
Hurricane | 4× | 6480 | 6743 | 8551 | . | 7258 | NS | 28.4 | |
Jackson | 2× | 5673 | 7817 | 8271 | 8212 | 7493 | 1180 | 24.3 | |
Jumbo | 4× | 6645 | 7605 | 9178 | 7810 | 7810 | NS | 21.7 | |
King | 2× | 5312 | 7148 | 7675 | 8807 | 7236 | NS | 22.5 | |
Lonestar | 2× | 7525 | 8136 | 11,306 | 9456 | 9106 | NS | 27.1 | |
Marshall | 2× | 5462 | 8051 | 7975 | 9073 | 7640 | 1322 | 29.1 | |
Maximus | 4× | 6791 | 8121 | . | 8776 | 7896 | NS | 19.5 | |
Multimo | 4× | 4739 | 7114 | 6159 | 11451 | 7366 | 2401 | 28.4 | |
Passerel Plus | 2× | 6168 | 7877 | 8846 | 8794 | 7921 | 1116 | 16.1 | |
Prine | 4× | 5950 | 7489 | 9950 | 8429 | 7955 | 1702 | 22.0 | |
Rio | 2× | 6095 | 8067 | 8104 | 8911 | 7794 | 1073 | 18.8 | |
TAM90 | 2× | 5631 | 7853 | 8200 | 8334 | 7505 | 1275 | 23.9 | |
Tetragold | 4× | 6593 | 7306 | 6048 | . | 6649 | NS | 29.9 | |
Verdue | 4× | 6141 | 8049 | . | 9094 | 7761 | NS | 21.1 | |
Mean | 6093 | 7549 | 8208 | 8871 | 7614 | ||||
LSD0.05 | 416 | 343 | NS* | 558 | |||||
CV % | 9.4 | 7.5 | 7.4 | 7.9 | |||||
*NS: No Significance.
and Multimo. The difference between the greatest and least producing variety by location was 3233, 1528, 5271 and 4315 kg∙ha−1 at Poplarville, Newton, Raymond and Starkville respectively. The greatest difference between the greatest and least values was observed in Raymond which was the only location that was not significant among varieties.
Marshall annual ryegrass performance for the state of Mississippi was near average among the means in all locations while Lonestar, Prine, and Hercules were among the top producers. Although Marshall annual ryegrass remained above the mean across the state, Gulf was one of the lowest yielders among the 20 varieties. Raymond was the only location that did not have influence on varietal performance. Ryegrass in Poplarville and Newton on average produced the lowest yields across the state with Poplarville producing 32% less forage than Stark- ville, where the greatest yields were recorded.
Areas along the coastal zone of the state are characterized by mild, wet winters and occasional crown rust is- sues, which may lend producers to consider using tetraploid varieties. However, in the central and northern re- gions of Mississippi, varietal stability across the state may be one method of recommendation. Varieties with the greatest yield across all locations would include only Lonestar, Hercules, and Maximus. Another method of va- rietal selection may include the function of maturity and cold tolerance. In Mississippi, varieties classifieds as mid to late maturing with at least medium cold tolerance were the greatest producers. However, very few varie- ties with early maturities were present in the data and no varieties with an early maturity and high cold tolerance was present, with the exception of Lonestar. Consequently, Lonestar produced the greatest forage yields in the state.
Ryegrass variety selection is as much a consideration of management implementation as it is about yield. This study was limited to yield results from variety testing while maturity, fiber quality, and disease pressure may have been important to evaluate as well. Considering data from this paper, recommendation of varieties may need to be adjusted especially in specific regions. Recent tetraploid marketing strategies has influenced many producers in the state, but those advantages may only be isolated to certain areas. Some older varieties may be cheaper to sow while performing similar to new more expensive releases. Similarly some varieties may be well documented to perform well, but have been rarely utilized. Varieties should be evaluated overtime over several years and locations to properly assess the adaptability of that variety to a given area.
Improvement of annual ryegrass forage yield from 1987-2012 was evident for most locations across Missis- sippi. This increase could be attributed to the obligatory out-crossed nature of annual ryegrass. Genetic variabil- ity or genetic drift may have shifted within the population of the variety allowing for increases in yield with no explainable environmental changes. Such conclusions may aid in future plant selection for Mississippi which may need to forgo polyploidy induction and focus other genetic improvements among top producing varieties.