Genetic Diversity of Gossypium hirsutum and G. barbadense in the US National Cotton Germplasm Collection.

An understanding of the genetic diversity of Gossypium hirsutum and G. barbadense cotton in the US National Cotton Germplasm Collection is essential to develop strategies for collection, conservation, and utilization of these germplasm resources. The US Collection includes accessions with improved yield and fiber quality within cultivated types of these species, as well as accessions possessing sources of abiotic and biotic stress resistance often found in wild types.  We have used a core set of 105 SSR markers to characterize 1,541 G. hirsutum accessions and 430 G. barbadense accessions.  We will evaluate G. hirsutum and G. barbadense in terms of overall variation and variation within sub-groups of cultivated and wild types.  Several botanical races have been described within the wild types of both species.  We will examine the molecular information to determine if these races truly exist at a genetic level.  Introgression between G. hirsutum and G. barbadense will be measured and its role in variation within these species will be established.