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:The pink bollworm (Pectinophora gossypiella) is one of the world's most destructive pests of cotton. This invasive lepidopteran occurs in nearly all cotton-growing countries. Its presence in the Ord Valley of North West Australia poses a potential threat to the expanding cotton industry there. To assess this threat and better understand population structure of pink bollworm, we analysed genomic data from individuals collected in the field from North West Australia, India, and Pakistan, as well as from four laboratory colonies that originated in the United States. We identified single nucleotide polymorphisms (SNPs) using a reduced-representation, genotyping-by-sequencing technique (DArTseq). The final filtered dataset included 6355 SNPs and 88 individual genomes that clustered into five groups: Australia, India-Pakistan, and three groups from the United States. We also analysed sequences from Genbank for mitochondrial DNA (mtDNA) locus cytochrome c oxidase I (COI) for pink bollworm from six countries. We found low genetic diversity within populations and high differentiation between populations from different continents. The high genetic differentiation between Australia and the other populations and colonies sampled in this study reduces concerns about gene flow to North West Australia, particularly from populations in India and Pakistan that have evolved resistance to transgenic insecticidal cotton. We attribute the observed population structure to pink bollworm's narrow host plant range and limited dispersal between continents.
Project description:The pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), is a major global pest of cotton. Current management practices include chemical insecticides, cultural strategies, sterile insect releases, and transgenic cotton producing crystalline (Cry) protein toxins of the bacterium Bacillus thuringiensis (Bt). These strategies have contributed to the eradication of P. gossypiella from the cotton-growing areas of the United States and northern Mexico. However, this pest has evolved resistance to Bt cotton in Asia, where it remains a critical pest, and the benefits of using transgenic Bt crops have been lost. A complete annotated reference genome is needed to improve global Bt resistance management of the pink bollworm. We generated the first chromosome-level genome assembly for pink bollworm from a Bt-susceptible laboratory strain (APHIS-S) using PacBio continuous long reads for contig generation, Illumina Hi-C for scaffolding, and Illumina whole-genome re-sequencing for error correction. The pseudo-haploid assembly consists of 29 autosomes and the Z sex chromosome. The assembly exceeds the minimum Earth BioGenome Project quality standards, has a low error rate, is highly contiguous at both the contig and scaffold levels (L/N50 of 18/8.26 MB and 14/16.44 MB, respectively), and is complete, with 98.6% of lepidopteran single-copy orthologs represented without duplication. The genome was annotated with 50% repeat content and 14,107 protein-coding genes, further assigned to 41,666 functional annotations. This assembly represents the first publicly available complete annotated genome of pink bollworm and will serve as the foundation for advancing molecular genetics of this important pest species.
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.