Working group session:
Germplasm and Genetic Stocks
Presentation type:
oral
Authors:
Percy, Richard; Hinze, Lori; Yu, John ; Fang, David; Gore, Michael ; Scheffler, Brian
Presenter:
Percy, Richard
Correspondent:
Percy, Richard
Abstract:
An understanding of the genetic diversity of cotton (Gossypium spp.) is essential to develop strategies for collection, conservation, and utilization of these germplasm resources. To define the diversity present in the U.S. National Cotton Germplasm Collection, a core set of 105 SSR markers were applied to analyze molecular relationships among 2,254 selected accessions, collectively known as the Gossypium Diversity Reference Set (GDRS). NTSYS software was used to generate a Jaccard similarity matrix of the accessions which was double-centered and used to calculate eigenvectors for plotting Principal Coordinate Analyses (PCoA). The first two principal coordinate axes explained ~27% of molecular variation among accessions. Two distinct clusters could be discerned among AD genome accessions that corresponded to the G. hirsutum and G. barbadense species. A third distinct cluster composed of A genome accessions was evident, and accessions of the remaining diploid genomes formed a fourth intermixed but distinct cluster. Accessions could be identified within the G. hirsutum and G. barbadense clusters that were either misclassified or the product of introgression. Structure could be discerned within G. hirsutum that related to recognized races, but distinct race clusters were not evident. Cultivated accessions of G. hirsutum were primarily confined to a small portion of the G. hirsutum cluster that also corresponded with the race latifolium - indicating the large contribution of that race to the variability observed in cultivated cotton. A good resolution of the diversity present in the cultivated tetraploid species was achieved, and will aid in maintaining the diversity and integrity of these species in the collection. However, weak resolution of variation among diploid species indicates a need for more informative markers to be developed to better define the diversity of those species within the germplasm collection.