Genetic diversity analysis in Bt introgressed and non-Bt lines of upland cotton (Gossypium hirsutum L.)

Diversity analysis of Bt lines, a prerequisite to heterosis breeding, are rarely published. Diversity analysis of 140 cotton genotypes comprising of BGI, BGII and Non-Bt lines resulted in the grouping of genotypes into 20 clusters among which fve had multiple genotypes and 15 others were solitary. Specific clustering of genotypes of BGI and BGII was not observed which got distributed across the clusters. The maximum and minimum inter-cluster distances were observed between two solitary clusters XVI and XVIII (159.8) as well as clusters VII and XI (6.4), respectively, refecting diverse and close relationship among the Bt genotypes of those clusters. Two pairs of isogenic lines were located in the same clusters as they shared the same genetic background. The genetic background played important role in the diversity rather than the Bt status of genotype. Also, the maximum genetic diversity (64%) was arising from traits which were not related to Bt genes such as plant height, boll weight, and ginning out-turn when compared to the characters related to Bt gnes such as seed cotton yield and boll number (33%). In general, for seed cotton yield, BGI outperformed BGII lines. The study helped in developing high yielding hybrids through diverse parental line selections.