Genetic diversity of 92 cotton accessions evaluated with SSR markers.

A set of 132 SSR markers,spanning the whole genome with an average of 5 SSRs per chromosome,were selected to genotype the natural population consisting of 92 accessions.Four hundred and ninety-four polymorphic bands were obtained with the average of 3.69 polymorphic bands per SSR marker.The polymorphism information content(PIC) for a marker locus is 0.010 0～0.871 4 with the average of 0.546 6.Jaccard's genetic similarity coefficients were calculated using the software of NTSYS-pc version 1.80.Mean pairwise genetic similarity coefficients of 92 cultivars(lines) was 0.729 2±0.135 0,with the range of 0.411 8 to 0.957 5.The percentage of pairwise similarity coefficient less than 0.800,is 48.94% and 50.91% for the upland accessions and sea-island accessions,respectively.This indicated that the genetic basis of natural population was broad to a certain extent.The UPGMA dendrogram based on Jaccard's similarity coefficients and the information of genealogy of accessions indicated that:these accessions were developed through a complex breeding process and the ancestry was multi-descent origins,which resulted that a high genetic diversity in some extent was preserved in the natural population.