Genetic basis of plasticity for forage quality traits in response to water deficit in a diverse germplasm panel of alfalfa

Plant phenotypic plasticity is the ability of plants to express different phenotypes in response to environmental variations. Genetic bases by which phenotypic plasticity affects plant adaptation to environmental change remain largely unknown. In the present study, we characterized 26 forage quality traits in a panel of alfalfa 198 accessions in a field trial under water deficit gradient. The regression analysis revealed that the values of fiber-related traits decreased, while those among energy-related traits increased, as water deficit increased. Genetic loci for forage quality traits were investigated by Genome-wide association studies (GWAS) under different levels of water deficit. Genetic loci associated with forage quality traits were identified and compared. Similar regions were found between energy-related traits when grand means were used for GWAS. Most of the associated markers were identified under water deficit, suggesting genetic mechanisms for forage quality traits were differ between well-watered and water stressed plants. Although GWAS on forage quality have been reported, we are the first to address the genetic factors for forage quality traits under water deficit in autotetraploid alfalfa. The information gained from the present study will be useful for the genetic improvement of alfalfa with enhanced drought/salt tolerance while maintaining forage quality.