Genetic Diversity in the USDA-GRIN Annual Ryegrass Germplasm Collection.

Despite its importance for breeding and germplasm conservation strategies, an assessment of the phenotypic and genotypic diversity present in the USDA-GRIN annual ryegrass (Lolium multiflorum Lamarck) collection has not been reported in the literature. The large size and heterogeneous structure of many plant germplasm collections in the GRIN system is a concern due to their high maintenance cost and incomplete utilization by the research community. In order to make germplasm management by curators more efficient and facilitate its utilization, core collections are created to represent most of the genetic diversity of a crop species in small populations. The objective was to measure and analyze the genetic relatedness among plant introductions in the annual ryegrass GRIN collection, 15 experimental lines from the UF/IFAS Annual Ryegrass Breeding Program and 13 commercial cultivars using phenotypic and molecular marker data. The specific objectives are: i) perform cluster analyses to create a core collection in annual ryegrass based on 15 morphological and agronomic characteristics that were evaluated in the field during the fall-winter-spring season of 2013-2014; ii) perform a molecular genetic diversity study using 48 EST-SSRs with the goal to elucidate the genetic diversity in those populations, and then produce a cluster based on the molecular data; and iii) determine the similarity between clusters created using phenotypic and molecular data.