Physiological characteristics of the anti-dichlorvos Nomuraea rileyi strains by UV mutagenized

Abstract:

[Background] Injurious insect (Noctuidae) tend to develop high resistance to chemical pesticides, some of them can increase the effect of some entomogenous fungi. There is a lack of research on Nomuraea rileyi in this part currently. [Objective] To explore the physiological characteristics of UV- mutant Nomuraea rileyi mutants, which are highly resistant to dichlorvos, a common organophosphate insecticide, including mycelial growth, sporulation and the activity of chitin enzyme. [Methods] Based on the mutant strains Nr-UVY1 and Nr-UVY6, which were screened by UV-induced mutagenesis of Nomuraea rileyi, the mycelial growth inhibition rate, the subculture sporulation amount, and the chitinase activity were measured by the addition of different concentrations of dichlorvos growth medium. [Results] On the medium containing 1 291 mg/L dichlorvos, the inhibition rate of dichlorvos on the mycelial growth of the original strain reached 100%, and the mutant Nr-UVY1 (42.38%) and Nr-UVY6 (37.01%) were far away lower than the original strain. According to the mycelial growth inhibition rate curve, when the treatment concentration was higher than 1 291 mg/L, the curves of the two mutant strains increased steadily and were much lower than the original strain, indicating that the resistance of the mutant strains to dichlorvos was remarkable and stable. On the medium with different concentrations of dichlorvos, the mycelial inhibition rate of the mutant strain Nr-UVY6 was smaller than that of the mutant strain Nr-UVY1, manifesting Nr-UVY6 was more resistant to dichlorvos. On the same culture conditions, the initial sporulation time of the two mutant strains was slightly later than the original strain, but the difference was not significant. The sporulation of the mutants was significantly higher than that of the original strains in each generation. In particular, the sporulation of Nr-UVY6 was always more than 2 times higher than the original strain and more stable. The chitinase activity measured by the transparent circle method, the mutant strain Nr-UVY6 was higher than Nr-UVY1 and the starting strain. [Conclusion] The mutant strains subjected to ultraviolet mutagenesis have much higher resistance to dichlorvos than the original strains, and exhibit better traits in growth and reproduction, and it is possible to further explore their level of pathogenicity due to their high activity of chitinase enzyme.