Deltamethrin resistance in Laodelphax striatellus had been associated with its oxidative detoxification by overexpression of four cytochrome P450 monooxygenases like CYP353D1v2, CYP6FU1, CYP6AY3v2, and CYP439A1v3. The first three P450s have been validated for insecticide-metabolizing capability and only CYP6FU1 was found to degrade deltamethrin. In this study, an investigation was conducted to confirm the capability of CYP439A1v3 to degrade deltamethrin. The CYP439A1v3 was first expressed in Sf9 cell line and its recombinant enzyme was tested for metabolic activity against different insecticides using substrate depletion assay combined with metabolite identification. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and carbon monoxide (CO)-difference spectra analysis showed that the intact cytochrome P450 protein was successfully expressed. Tests with probe substrates proved its enzyme activity, as p-nitroanisole, ethoxycoumarin, and ethoxyresorufin were preferentially metabolized (specific activity 7.767 ± 1.22, 1.325 ± 0.37, and 0.355 ± 0.37 nmol/min per mg of protein, respectively) while only luciferin-HEGE was not. In vitro incubation of the recombinant CYP439A1v3 protein with deltamethrin revealed hydroxylation by producing hydroxydeltamethrin. On the contrary, no metabolite/metabolism was seen with nonpyrethroid insecticide, including imidacloprid, buprofezin, chlorpyrifos, and fipronil. To the best of our knowledge, this is the first study to link a CYP450 from family 439 to confer pyrethroid resistance to L. striatellus. This finding should help in the design of appropriate insecticide resistance management for control of this strain of L. striatellus.
Rice is the main staple food crops for the Malaysian population. Rice is also susceptible to bakanae diseases caused by some Fusarium species and reducing yield, and quality of rice also profit. In this study, several rice fields were surveyed to collect Fusarium isolates associated with bakanae disease. The morphological features of Fusarium andiyazi isolates found on infected rice plants were identified in this investigation. For biological species identification, MAT-1 (Mating type idiomorphs) bearing isolates were crossed with MAT-2 isolates. Crossing was succeeded between cross of two different mating type bearing field isolates. Consequently, there is a possibility of exchange of genetic material within the F. andiyazi population in Malaysia. The identity of the isolates was further determined up to the species level by comparing DNA sequences and phylogenetic analysis of two genes. The phylogenetic analyses of the joined dataset of translation elongation factor 1-alpha (TEF1-α) and RNA polymerase subunit II (RPB2) revealed that all the isolates were F. andiyazi. In pathogenicity tests, F. andiyazi were found to be pathogenic on the susceptible rice cultivars MR211 and MR220. Inoculated rice seedling produced typical bakanae symptom like elongation, thin and yellow leaves. F. andiyazi was further confirmed as pathogenic species by Ultra High-Performance Liquid Chromatography (UPLC) detection of Gibberellic acid (GA3) and Fusaric acid. In this study, F. andiyazi strains have been identified as the responsible pathogen for causing rice bakanae disease in Malaysia and it is the first report of F. andiyazi, as a pathogenic species on rice in Malaysia.