Comparative Analysis of Genetic Diversity among Bt Cotton Genotypes Using EST-SSR, ISSR and Morphological Mar kers

Abstract

Robust information of genetic diversity among Bt cotton genotypes is still lacking and availability of several marker systems has prompted us to compare their utility for the detection of genetic diversity. Here, we report the comparative efficiency of morphological and molecular markers (EST-SSRs and ISSRs) in deter mining the genetic diversity among 30 Pakistani Bt cotton genotypes. Three different dendrograms base d on 20 EST- SSRs, 13 ISSRs and 20 morphological markers divided the 30 Bt cotton genotypes into five, six, and three clusters, respectively. EST-SS Rs and ISSRs revealed 0.73-1.00 and 0.77-0.97 genetics similarity among Bt cotton genotypes which indicated low level of genetic diversity. Further population structure ana lysis showed extensive allelic admixture among Bt cotton cultivars and identified three (EST-SSRs) a nd six (ISSRs) subgroups. The MGHES-31 (EST-SSRs) and UBC-807 and UBC-815 (ISSRs) showed maximum values of Polymorphic Information Contents ( PIC ) and Dj and had low value of Cj . The comparison of two marker systems showed that EST-SSRs had high value of Expected heterozygosity (H ep ) and low value of Marker Index (MI) as compared to ISSRs. In conclusion, high level of genetic similarity amo ng Bt cotton genotypes compel the plant breeders for the introduction of divers/exotic geno types in their breeding program and marker discriminating indices could be a potential tool for selection of particular marker system to unveil the genetic difference. Keywords: Confusion probability, Expected heterozygosity, Ma rker Index, Population structure analysis, Polymorphic information content s.