Classification of bentgrass (Agrostis) cultivars and accessions based on microsatellite (SSR) markers

Genetic relationships among Agrostis species used for turf have been difficult to discern. Recent studies have either confirmed or contradicted previously proposed genetic relationships based on chromosome pairing behavior of inter-specific hybrids. The objective of the current study was to assess genetic relationships among Agrostis cultivars and accessions by using newly available A. stolonifera microsatellite (SSR) markers. Nuclear SSR (nuSSR) and chloroplast SSR (cpSSR) markers were used to genotype 16 individuals from each of 74 Agrostis cultivars and accessions. Genetic relationships based on nuSSR markers most closely resembled species relationships proposed by Jones in the 1950s. Contrary to the work of Jones, genetic relationships based on cpSSR markers indicated that A. canina was more closely related to A. stolonifera than to A. capillaris. We hypothesize that chloroplast introgression via interspecific hybridization between A. canina and A. stolonifera resulted in these species sharing common chloroplast genome lineages, while maintaining disparate nuclear genome lineages. Genetic relationships within Agrostis species based on nuSSR markers closely matched known pedigree relationships. Bayesian clustering analysis of nuSSR markers indicated that most modern seeded A. stolonifera cultivars exhibited high levels of admixture. Our study confirms that nuSSR markers distinguish Agrostis species and cultivars, and are valuable for studying genetic diversity and genetic relationships within the genus Agrostis.