Effect Of Mutagens On Fungicide-resistance Of Lecanicillium Lecanii (Zimm.) Gam & Zare

Lecanicillium lecanii (Zimm.) Gam & Zare is a well-documented entomopathogenic fungi, which is highly effective in control of insects. Now many countries develop some biological preparation, such as Mycotal, Vertalec and so on. They play important roles in pest control. However, Lecanicillium lecanii is sensitive to most common fungicide, and can not be used with fungicide. This research aimed to find some mutants which have capacity of propamocarb resistance, investigate mutagenic effects of four different methods (they are low energy N⁺ ions implantation, Ultraviolet radiation, NTG mutagenesis and multiple mutation), establish some effective modes for other entomopathogenic fungi. Based on some experiments in the past two years, the useful results were got, as follows:1. Through the experiment of N⁺ implantation, an optimized condition was obtained. It involves N⁺ beam energy 30 kev, dose 1×10¹⁴ ions/cm², magnetic current 1.67μA. Treated by the parameter, mortality of conidia is 88.6%, positive-mutation rate is 11.4%, and positive-mutation range is 143.0%. It is not evident for the relations between treat times and fungicide-resistance of mutants. Propamocarb's effective concentration (EC₅₀) to this mutant is 1598.8 mg/L, which is 2.8 times higher than strain CA-14. Mutant's fungicide-resistance pass down stabled.2. Through the experiment of ultraviolet radiation, an optimized condition was obtained. It involves radiant distance is 45cm, radiation needs 60s, wavelength is 253.7nm, and energy is 20W. Treated by the parameter, mortality of conidia is 78.8%, positive-mutation rate is 7.7%, and positive-mutation range is 13.0%. Treated time under this condition is important for fungicide-resistance. After 4 times of UV treatment, a mutant's fungicide-resistance is 1070.4 mg/L, which is 2.1 times higher than strain CA-14. Mutant's fungicide-resistance pass down stabled.3. Through the experiment of NTG, an optimized condition was obtained. It involves NTG concentration 1mg/ml, 60 minutes, pH 6.0. Treated by the parameter, mortality of conidia is 84.6%, positive-mutation rate is 7.7%, and positive-mutation range is 135.5%. Treated time under this condition is important for fungicide-resistance. After 3 times of NTG treatment, a mutant's fungicide-resistance is 1418.2 mg/L, which is 2.8 times higher than strain CA-14. Mutant's fungicide-resistance pass down stabled.4. In uninterrupted complex mutation, two optimum modes were got. The first: Strain CA-14 and U-P4-F1, can get high fungicide-resistance after NTG treatment and ions implantation. Their mutants' capacity is 3 times more than sensitive stain. Mutagenic effects are: mortality of conidia is 90.7%⁹4.4%, positive-mutation rate is 11.2%¹3.3%, and positive-mutation range is 42.7%¹97.2%, EC₅₀=1496.7-1527.2mg/L. The second: Strain L-P3-F5, which was treated byion beam once and got certain ability of fungicide-resistance, can get higher fungicide-resistance after NTG treatment, ions implantation and UV at the same time. Mutants' capacity is 3.8 times more than sensitive stain. Mutagenic effects are: mortality of conidia is 91.5%, positive-mutation rate is 7.7%, and positive-mutation range is 20.2%, EC50 is 1992.0mg/L. The fungicide-resistance capacity of mutants, which are obtained by uninterrupted complex mutagenesis, is better than that of mutants, which were got by single-factor mutation.5. An optimum mode about complex mutation was obtained, which involves NTG mutation, and then Ultraviolet radiation, and then ions implantation, and 3 multiple factor (ion beam, NTG, UV) treatment at last. In this section, 4 factors' mutational contributeve rate are: ion beam > NTG > 3 multiple factor (ion beam, NTG, UV) > UV. In conclude, the effect of complex mutation is better than that of single-factor mutation, the effect of interval-complex mutation is better than that of uninterrupted-complex mutation. 3 mutants which have high capacity of fungicide-resistance were obtained after treated with this mode. These EC50 at 2164.4 to 2693.5 mg/L, fungicide-resistance level at 4.3 to 5.4. On recommendatory concentration, sensitive strain CA-14's germination rate is 2.4%, while mutants' is more than 78.0%. Therefore, mutants can be used with Propamocarb in agriculture.