Development of a Core Collection Based on EST-SSR Markers and Phenotypic Traits in Foxtail Millet [Setaria italica (L.) P. Beauv.]

The germplasm resources of foxtail millet reserve diverse genes for crop improvement which needs to be explored. To comprehend the maximum genetic diversity of this crop, a core collection with minimum number of accessions will facilitate easy access to genetic material. Here we assessed the genetic diversity and population structure in a large germplasm collection of 785 accessions by employing EST-SSR markers and morphological traits. A total of 107 alleles were detected with an average allele number of 4.9 per locus among the 785 accessions based on 22 EST-SSR markers. The number of alleles per locus ranged from 2 to 8. Polymorphism information content and expected heterozygosity ranged from 0.355 to 0.738 (mean = 0.525) and 0.451 to 0.771 (mean = 0.603), respectively. The germplasm collection was separated into three groups based on population structure analysis, whereas principal coordinate analysis (PCoA) could not cluster accessions according to their geographic origin. Subsequently, a core collection with a total of 170 accessions (21.66%) was selected from the whole set of germplasm by combining allelic variations of 22 EST-SSR markers and eight different phenotypic traits. The core collection optimally represented the whole germplasm collection and displayed a similar level of genetic diversity, population structure, and phenotypic variations based on various genetic analyses such as Shannon-Weaver and Nei’s diversity indices and PCoA, while phenotypic traits were analyzed by mean, range, and principal component analysis. This core collection of foxtail millet will be a primary resource for further genetic analysis and development of appropriate breeding strategies.