Genetic parameters for phenotypic traits in annual ryegrass

Abstract

Characterizing phenotypes in germplasm collections and making data publicly available is crucial to ensure the utilization of the accessions in breeding programs. Variance component estimates are used to calculate genetic parameters needed to make strategic decisions for germplasm conservation and its utilization in plant breeding. This information is lacking for annual ryegrass (Lolium multiflorum Lamarck) germplasm from the USDA National Plant Germplasm System (NPGS). In this study, we estimated variance components, repeatability, genotypic values, genetic correlations, and genotype ´ year correlations for 18 traits in 167 annual ryegrass populations. Repeatability (H2) ranged from 0.11 to 0.93 for single-year analyses, and from 0.03 to 0.86 for traits evaluated during two growing seasons, evidencing the presence of genetic variability. Genotype ´ year correlations ranged from 0.17 up to 0.99, demonstrating variable consistency in phenotypic performance across years. Combining multiple traits in one cultivar is a challenge for breeders, particularly for traits negatively correlated. Establishment, plant vigor, leaf width and length, and chlorophyll content were negatively correlated with disease traits. Heading date was positively correlated with number of tillers, crown size, and biomass production. High positive correlations were also found between biomass and plant height, crown size, tiller number and size, and leaf/stem ratio. The data presented in this study will become publicly available via the Germplasm Resource Information Network (GRIN)-Global database of the NPGS.