The investigation of factors potentially involved in resistance to Bacillus thuringiensis in native Plutella xylostella (l.) (Lepidoptera: Plutellidae) populations

Author(s)

Caroline Placidi De Bortoli

• Document type: Doctoral Thesis
• Press: Jaboticabal. 2018-02-22.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2018-02-16
• Advisor: Ricardo Antonio Polanczyk

Abstract

Plutella xylostella is a major insect pest of cruciferous crops worldwide. Although controlled with both synthetic and biological insecticides it can rapidly evolve resistance to a variety of insecticides. The most common biopesticides used to control P. xylostella are based on the entomopathogenic bacterium Bacillus thuringiensis. Although many studies have been performed on Bt, the mode of action is still not fully understood. A wide diversity of genes are differentially expressed in the midgut of resistant insects, this suggests that a variety of cell processes may be involved in the preservation of resistance. Recent discoveries have shown that mutations in the gene encoding an ABCC2 transporter are responsible for resistance to Bt toxins in various different insect species. The aim of this research was to test the hypothesis that the susceptibility of P. xylostella to Bt correlates with the level of expression of components of this putative stress-response regulon. The level of expression of ALP, APN, CDKAL 1, MAP4K4 and ABCC2 genes were compared using qPCR, between susceptible and resistant P. xylostella populations. The investigation of the DNA sequence of ABCC2 cDNA was performed, through PCR and sequencing, to test the hypothesis that the susceptibility of P. xylostella to Bt correlates with mutations on the ABCC2 gene. Backcrosses between susceptible and resistant populations and complementation cross between resistant populations were performed. Our research demonstrated that there were no patterns in the expression of the genes tested demonstrating no association between expression and resistance/susceptibility. However, when investigating the ABCC2 gene sequence, a mutation in the gene of the Brazilian resistant population was found, which could be responsible for the resistance of the Brazilian population studied in this research. Backcrossing assays didn’t confirm that the resistance was due to the 1bp deletion found, however complementation assays indicated that the resistant Brazilian population shares a resistance allele with the resistant Hawaiian population. (AU)

• FAPESP's process: 15/05891-6 - THE INVESTIGATION OF FACTORS INVOLVED IN RESISTANCE TO Bacillus thuringiensis BERLINER IN NATIVE Plutella xylostella (L., 1758) (LEPIDOPTERA: PLUTELLIDAE) POPULATIONS.
• Grantee: Caroline Placidi de Bortoli
• Support Opportunities: Scholarships in Brazil - Doctorate