Patterns of Genetic Variation Suggest Introgression Between Zoysia Species.

Zoysia spp. are warm-season turfgrasses widely used across the southern United States in residential lawns, commercial landscapes, and golf courses for their superior heat and drought tolerances. Information regarding the population structure and levels of admixture present within U.S. germplasm collections can aid in the maintenance of genetic variability as well as the capacity to exploit it. The objectives of this study were to gauge levels of allelic diversity present within and among Zoysia spp. using simple sequence repeats (SSRs), assess the genetic constitution of putative interspecific hybrids, and measure the phenotypic variability of inflorescence traits of Zoysia spp. as well as putative interspecific hybrids. A genotypically and phenotypically diverse set of sixty-two Zoysia accessions were genotyped using fifty SSR markers. Three hundred and seventy-seven SSR alleles were scored. Polymorphic information content for most of the SSRs was high (average of 0.49) as well as was heterozygosity (0.56). A continuous range of variation within and among the species was revealed in both UPGMA cluster and PCO analyses. Three unique subpopulations, two of which were Z. japonica-specific and the third being Z. matrella-specific, were identified using the model-based program, STRUCTURE. Evidence of admixture was found in twenty-three Zoysia accessions. A continuous range of variation was also discovered between accessions based on six inflorescence phenotypes. LS means were significant between Z. japonica and Z. matrella when putative interspecific hybrids were separated in the analysis. Based on all these results, this study was able to validate the existence of Z. japonica x Z. matrella hybrids, which speaks to both the historical and future applicability of hybrid-based breeding strategies within zoysiagrass.