Determination of fungal pathogens of Hypera postica (Gyllenhall) (Coleoptera: Curculionidae): isolation, characterization, and susceptibility

WOS: 000436823500002Background: Fungal pathogens of Hypera postica (Gyllenhall) (Coleoptera: Curculionidae) were collected from the vicinities of Adana and Igdir in Turkey. The pathogenicity of the fungal isolates against the pest were investigated. According to morphologic (colony morphology, spore shape) and molecular (sequences of ITS1-5.8S ITS2 region and EF1-a, Bloc, and RPB1 genes) characterizations, the isolates were identified as Beauveria bassiana (HpI-2, HpI-6, HpI-7, HpI-10, HpA-3, HpA-4, HpA-5) and Beauveria pseudobassiana (HpI-4). All these strains were isolated from H. postica for the first time. In order to determine pathogenesis of all isolates on the target pest, bioassays were conducted against larvae and adults, as screening of (1 x 10(7) conidia/ml) and dose-response (1 x 10(5), 1x10(6), 1 x 10(7), 1x10(8), conidia/ml), under laboratory conditions. The fungal isolates, closely related to each other, yielded significantly varied mortalities on larvae and adults. H. postica larvae were found more susceptible than adults to the fungal isolates in all tests. The highest mortality rates (100 and 98%) for larvae and adults, respectively, were obtained by B. bassiana strain HpA-5 within 14 days at 1 x 10(8) conidia/ml concentration. The median lethal concentration (LD50) of HpA-5 required to kill the larvae and adults of H. postica at concentrations of 2.37 x 10(4) and 1.4 x 10(5) conidia/ml, respectively. These results are promising; therefore, the B. bassiana strain HpA-5 can potentially be used against H. postica

Comparison of the potential activities of viral and bacterial chitinases

Abstract Background Chitin, a long-chain polymer of N-acetylglucosamine, is a major structural component of the insect exoskeleton and the peritrophic membrane (PM). Chitinases are able to effectively break down glycosidic bonds of chitin polymer thus can be used in agriculture to control plant pathogen insects. These enzymes can be synthesized by higher plants, animals, protista, bacteria, and viruses. Results In this study, viral and bacterial chitinases were compared for their potential activity on a laboratory test insect. The genes encoding chitinases of Autographa californica nucleopolyhedrovirus (AcNPV) and Cydia pomonella granulovirus (CpGV) were amplified from genomic DNAs by PCR and cloned into the pET-28a (+) expression vector. The chitinase proteins of these 2 viruses (AcNPV-Chi, CpGV-Chi) and Serratia marcescens chitinase C (ChiC) protein which was previously cloned were overexpressed in Escherichia coli. Expressed proteins were purified and confirmed by western blot analysis as 50, 63, and 68 kDa for AcNPV, CpGV, and S. marcescens chitinases, respectively. Enzyme activities of the chitinases were confirmed. Chitinases were also compared to each other in silico. The insecticidal effects of these proteins were evaluated on Galleria mellonella L. larvae. Bioassays were performed on the 3rd instar larvae for each chitinase protein in triplicate. The results showed that although there were differences in enzymatic activities and domain organizations, all 3 microbial chitinases produced almost the same level of insecticidal activity on the test insect. LC50 and LT50 values were compatible with the mortality results. These results were a preanalysis for comparing the effects of microbial chitinases. Conclusion Potential activity experiments should be carried out on more insects to provide detailed information on the insecticidal effects of bacterial and viral chitinases