Molecular Diversity Revealed by AFLP Markers in Upland Cotton Genotypes

Cotton is an important fiber crop grown over tropical and subtropical regions worldwide. The narrow genetic base of the cotton germplasm being used in breeding programs is one of the factors in failing to achieve appreciable amount of progress in improving fiber traits. Molecular markers have been successfully applied to estimate genetic diversity, besides their use in advancing the breeding cycle. Sixty upland genotypes from a cooperative regional testing program were screened with AFLP markers. Louisiana genotypes possessed coarse fibers, medium staple, and strong fibers, while heat tolerant genotypes showed high variability for these traits. The pairwise kinship estimates ranged between 0.1-0.88, while the PIC values ranged from 0.15-0.30, accounting for most of the shared ancestral alleles. The estimates of genetic diversity were in the range of 0.1-0.34. PCoA, and correspondence and UPGMA clustering methods showed no obvious grouping of the genotypes in line with their geographical origin. Some of genotypes, such as AU 5367, Acala 1517-99, and LA 05307025, were highly diverse from rest of the population. The DICE distance estimates among all the 60 genotypes reached a maximum of less than 0.15, indicating the relative lack of genetic diversity in this group of genotypes based on the markers used in this study.