Segregation of Genes in the Seeds Produced by F Bollgard II Cotton Differs between Hybrids: Could This Be Linked to the Observed Field Resistance in the Pink Bollworm?

Indian populations of the Pink Bollworm (PBW) are resistant to Bt () cotton hybrids containing and genes. Segregation of these genes in F hybrids could subject PBW to sublethal concentrations. Moreover, planting hybrids with varying zygosities of genes could produce diverse segregation patterns and expose PBW populations to highly variable toxin concentrations. This could potentially promote the rate of resistance development. Therefore, we studied the segregation patterns of genes in different commercial Bt hybrids cultivated in India. Results showed that two hybrids segregated according to the Mendelian mono-hybrid ratio, three segregated according to the Mendelian di-hybrid ratio, and one showed a mixed segregation pattern. The assortment of seeds containing genes varied between bolls of the same hybrid. In India, different Bt cotton hybrids are cultivated in small patches next to each other, exposing PBW populations to sublethal doses and wide variations in the occurrence of genes. It is necessary to avoid segregation of genes in the seeds produced by F hybrids. This study recommends using Bt parents homozygous for genes in commercial Bt cotton hybrid development. This breeding strategy could be effective for similar transgenic crop hybrids as well.