Long-Term Summary of Ryegrass Varieties and Ploidy Types in Mississippi

Abstract

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.