Genetic diversity in cultivated and wild Cotton (Gossypium sp.) in relation to responses to Alternaria leaf spot

Molecular analysis of susceptible and resistant genotypes of cotton using ISSR primers revealed that out of 27 primers used, 20 primers showed polymorphism. Total 112 bands were generated with amplification of these markers. Ninety bands were found to be polymorphic, out of which 8 were unique and 22 were monomorphic. The size of amplification product ranged from 126 bp to 999 bp. The ISSR marker, ISSR-8932808 amplified maximum number of bands (10) followed by ISSR-817 (9 bands) and ISSR-841 (8 bands). Maximum number of bands (7) specific to wild species G. raimondii which is resistant genotype, five bands specific to resistant genotype JLA 794 while 3 bands were specific to resistant wild genotype G. armourianum. One specific band IS-12-493 bp was specific to susceptible genotypes RHC 717, LRA 5166, RCH 603, RHH 707 and GSIV 218 while, ISSR-8932801-422 bp band was absent in resistant genotype so this band may be specific to susceptible genotypes. In case of cluster analysis genotypes viz. Mallika, G. armourianum, JLA 794 and G. raimondii formed independent cluster which are resistant to Alternaria blight disease.