Project description:Two strains of pink bollworm (Pectinophora gossypiella) selected in the laboratory for resistance to Bacillus thuringiensis toxin Cry1Ac had substantial cross-resistance to Cry1Aa and Cry1Ab but not to Cry1Bb, Cry1Ca, Cry1Da, Cry1Ea, Cry1Ja, Cry2Aa, Cry9Ca, H04, or H205. The narrow spectrum of resistance and the cross-resistance to activated toxin Cry1Ab suggest that reduced binding of toxin to midgut target sites could be an important mechanism of resistance.
Project description:Pink bollworm, Pectinophora gossypiella (Saunders) infestation on Bt cotton is a major concern to cotton production in India. The genetic diversity and phylogeographic structure of the insect in light of PBW resistance needs to be revisited. The objective of this study was to identify different haplotypes of pink bollworm and their distribution in India. To achieve this we studied the population structure in 44 cotton growing districts of India. The partial mitochondrial COI sequence analyses of 214 pink bollworm populations collected from 44 geographical locations representing 9 cotton growing states of India were analysed. Genetic diversity analysis exhibited presence of 27 haplotypes, among them Pg_H1 and Pg_H2 were the most common and were present in 143 and 32 populations, respectively. Distributions of pairwise differences obtained with partial COI gene data from the overall Indian populations are unimodal, suggesting population expansion in India. Significant neutrality test on the basis of Tajima' D and Fu's Fs presented a star-shaped haplotype network together with multiple haplotypes. The unimodal mismatch distribution, rejection of neutrality test with significant negative values supported the theory of demographic expansion in cotton pink bollworm populations in India. Genetic data not only provides us with a perspective of population genetics, but also that the two populations of pink bollworm, those occurring early in the season are genetically close to the late season populations with respect to their partial CO1 region. Resistance to Cry toxins does not seem to have had an impact on this region of the mt DNA in populations of pink bollworm.
Project description:In order to develop integrated management approaches for Pectinophora gossypiella, basic studies are crucial. The two-sex life table is the most important tool for describing the fitness and population parameters of both sexes (male and female) of an insect, while the traditional life table only explains the female sex of an insect. However, no study has reported on the biology of P. gossypiella using two-sex life table tools. Therefore, this study explains the rearing dynamics of P. gossypiella on a cotton seed-based artificial diet and a natural diet (mature cotton bolls). According to the results, the oviposition period of P. gossypiella was recorded to be longer on the artificial diet (9.07 ± 0.24) compared to the natural diet (7.40 ± 0.11). The total fecundity of P. gossypiella was greater on the artificial diet (125.94 ± 3.06) in comparison to the natural diet (60.37 ± 1.10). The population parameters, including intrinsic rate of increase, finite rate of increase, gross reproductive rate, and net reproductive rate of P. gossypiella were highest on the artificial diet in comparison to the natural diet. This study concluded that the cotton seed-based artificial diet was most suitable for the rearing of P. gossypiella. In the future, P. gossypiella may be studied in depth in light of the findings in this study.
