Molecular Diversity and Population Structure of Worldwide Collection of Cultivated Tetraploid Alfalfa (Medicago sativa subsp. sativa L.) Germplasm Revealed By Microsatellite Markers

Information on genetic diversity and population structure of tetraploid alfalfa across the world promotes effective use of genetic resources. A set of 336 worldwide collection of cultivated tetraploid alfalfa (Medicago sativa subsp. sativa) were genotyped using 85 genome-wide distributed SSR markers to establish the genetic diversity and population structure in alfalfa. Genetic diversity analysis identified a total of 1056 alleles across 85 marker loci. While the average expected heterozygosity and the polymorphism information content (PIC) values were 0.677 and 0.638, respectively, showing high levels of genetic diversity in cultivated tetraploid alfalfa germplasm. Comparison of genetic characteristics across chromosome indicated regions of chromosomes 2 and 3 had the highest genetic diversity. A higher genetic diversity was detected in alfalfa landraces than that of wild materials and cultivars. Two populations were identified by model-based population structure, principal component analysis and neighbor-joining corresponding to China and other parts of the world. Lack of strictly correlation between clustering of geographic origin, suggested common genetic background of alfalfa accessions from diverse geographic regions and extensive germplasm exchange. Establishment of genetic diversity, and population structure in this study could be useful for genetic and genomic analysis and utilization of the genetic variation in alfalfa.