STRUCTURE ANALYSIS OF GENETIC DIVERSITY IN TETRAPLOID AND DIPLOIDCOTTON GENOTYPES

Diploid and tetraploid Cotton cultivars are cultivated in Iran and are considered as an important fiber plant of the country. Due to long time cultivation and selection for specific traits, decrease in genetic diversity occurs and we need to improve genetic diversity of the germplasm available by hybridization among diverse cultivars. Therefore, the present study considers assessment of genetic diversity of some inter-specific cotton hybrids and their parental genotypes in G. hirsutum and G. barbadense as well as G. herbaceum and G. arboreum by using thirty homo and hetero ISSR markers. Genetic diversity parameters were determined among the hybrids. AMOVA test showed significant genetic difference among the genotypes and STRUCTURE analysis revealed allele admixture among cultivars. Network analysis of cotton genotypes showed the occurrence of gene exchange/allelic similarity between the genotypes. Some common alleles also were observed between diploid and tetraploid genotypes. Q matrix constructed by STRUCTURE program showed close affinity between diploid genotypes supporting NJ tree. These results indicate that although due to continuous selection of Iranian cotton cultivars we may have narrowed the available cotton gene pool we still find good genetic diversity within both diploid and tetraploid cultivars. A higher level of genetic diversity is present in both inter and intraspecific hybrids.