Data from: Genetic diversity of the two commercial tetraploid cotton species in the Gossypium Diversity Reference Set

A diversity reference set has been constructed for the Gossypium
accessions in the U.S. National Cotton Germplasm Collection to facilitate
more extensive evaluation and utilization of accessions held in the
Collection. A set of 105 mapped simple sequence repeat markers were used
to study the allelic diversity of 1,933 tetraploid Gossypium accessions
representative of the range of diversity of the improved and wild
accessions of G. hirsutum and G. barbadense. The reference set contained
410 G. barbadense accessions and 1,523 G. hirsutum accessions. Observed
numbers of polymorphic and private bands indicated a greater diversity in
G. hirsutum as compared to G. barbadense as well as in wild type
accessions as compared to improved accessions in both species. The markers
clearly differentiated the two species. Patterns of diversity within
species were observed but not clearly delineated, with much overlap
occurring between races and regions of origin for wild accessions and
between historical and geographic breeding pools for cultivated
accessions. Although the percentage of accessions showing introgression
was higher among wild accessions than cultivars in both species, the
average level of introgression within individual accessions, as indicated
by species-specific bands, was much higher in wild accessions of G.
hirsutum than in wild accessions of G. barbadense. The average level of
introgression within individual accessions was higher in improved G.
barbadense cultivars than in G. hirsutum cultivars. This molecular
characterization reveals the levels and distributions of genetic diversity
that will allow for better exploration and utilization of cotton genetic
resources.