Genetic diversity studies of elite cotton germplasm lines using RAPD markers and morphological characteristics

Genetic diversity was studied in a set of 30 elite cotton germplasm lines using RAPD markers and morphological characteristics. These included 20 genotypes of G. hirsutum, seven of G. arboreum, one genotype each of G. herbaceum, G. thurberi and G. klostzschianum. For RAPD analysis 32 random oligonucleotide primers were used and only 25 showed amplification. A total of 108 bands amplified in 30 genotypes of which 4 were present uniformly in all the 30 genotypes. One primer, Oligo 656, amplified an 1100bp G. arboreum specific band. Total bands amplified for each primer ranged from 1 to 8, with an average of 4.4 fragments per primer. Nei and Li's similarity coefficient estimates ranged from 0.5 to 0.9. The wild species G. klostzschianum showed the least similarity coefficient of 0.5 with all the lines of G. hirsutum, G. arboreum and G. herbaceum as well as with another wild species G. thurberi. Within G. hirsutum and G. arboreum, the similarity coefficient ranged from 0.6 to 0.9. Clustering was done using the symmetric matrix of similarity coefficients and cluster obtained based on Unweighted Pair Group Method based on Arithmetic Average (LTGMA). All the G. hirsutum genotypes except NPL 83 group in one cluster. The G. arboreum genotypes group in two clusters and the two wild species G. thurberi and G. klostzschianum formed independent groups. At 80% similarity 15 of the 20 G. hirsutum genotypes grouped in one cluster thereby revealing a very narrow genetic base. More or less similar clusters were obtained based on nine morphological characteristics measured on the genotypes in the field experiments. Results reveal a narrow genetic base within hirsutum and within arboreum groups.