Genetic Diversity and Local Adaption of Alfalfa Populations (Medicago sativa L.) under Long-Term Grazing

Abstract

Genomic information on alfalfa adaptation to long-term grazing is useful for alfalfa genetic improvement. In this study, 14 alfalfa populations were collected from long-term grazing sites (> 25 yrs) across four soil zones in western Canada. Six agro-morphological and three nutritive value traits were evaluated from 2018 to 2020. The genotyping-by-sequencing (GBS) data of the alfalfa populations and environmental data were used for genotype-environment association (GEA). Alfalfa cultivars released between 1926–1980 were used to determine degree of genetic variation of the 14 populations. Both STRUCTURE and UPGMA based on 19,853 SNPs showed that the 14 alfalfa populations had varying levels of parentages from alfalfa sub-species Medicago sativa and M. falcata. The linear regression of STRUCTURE membership probability on phenotypic data indicated genetic variations of forage dry matter yield, spring vigor and plant height were low, but genetic variations of regrowth, fall plant height, days to flower and crude protein were still high for the 14 alfalfa populations. The GEA identified 31 SNPs associated with 13 candidate genes that were mainly associated with six environmental factors of the long-term grazing sites. Candidate genes underlying environmental factors were associated with a variety of proteins, which were involved in plant responses to abiotic stresses, i.e., drought, cold and salinity-alkali stresses.