Enhanced fungicide resistance inIsaria fumosoroseafollowing ionizing radiation-induced mutagenesis

Abstract

The application of entomopathogenic fungi such as Isaria fumosorosea to combat insect pests on plants is complicated by their sensitivity to commonly used fungicides. In this study, I. fumosorosea mutants with enhanced resistance to the fungicide benomyl were induced by irradiation using either ion beams or gamma rays, or a combination of the two. When grown on agar containing benomyl, mycelial growth was observed for five of the six mutant isolates at benomyl concentrations that were more than 2000-fold those observed for the wild-type isolate (EC50 : > 5000 mg L(-1) c.f. EC50 : 2.5 mg L(-1) for the wild-type isolate). The mutant isolates evaluated also showed enhanced resistance to other fungicides at recommended field application rates. No differences were observed at the β-tubulin locus between the wild-type and the mutant isolates, suggesting that the enhanced benomyl resistance was not attributable to mutations in that gene. Ion beams and gamma rays are thus potentially useful tools for inducing beneficial fungal mutations and thereby improving the potential for application of entomopathogenic fungi as microbial control agents.

Benomyl-resistant Beauveria bassiana (Hypocreales: Clavicipitaceae) mutants induced by ion beams

“…This increased sensitivity may result from negative cross-resistance between benzimidazole fungicides and N-phenylcarbamate fungicides, such as diethofencarb (Fujimura et al 1992;Ziogas and Girgis 1993). Overall, fungicides indicating positive or negative cross-resistance in the present study were similar to fungicides in our recent observations for ion beam irradiation-induced benomyl-resistant mutants of I. fumosorosea (Shinohara et al 2013).…”

“…In conclusion, this study indicates that ion beams are useful tools for enhancing fungicide resistance in B. bassiana, as has previously been shown for I. fumosorosea (Shinohara et al 2013). Fungicide-resistant mutants produced in this way could be useful agents for biological control within IPM programs using fungicides, once they have been evaluated for other important characteristics, particularly virulence to target insects.…”

“…However, in our study the glutamate was replaced with alanine (E198A). The potential mechanisms for benomyl-resistance may be different between B. bassiana and I. fumosorosea, because no mutation at position 198 of the β-tubulin locus was detected in benomyl-resistant I. fumosorosea mutants produced by ionbeam irradiation (Shinohara et al 2013). …”

“…For example, ion beams have been used to produce mutants of Cordyceps militaris (L.) Link with enhanced production of the medical compound cordycepin (Das et al 2008). To the best of our knowledge, there has only been one other report of the use of ion beams on an entomopathogenic fungus, Isaria fumosorosea Wize, to enhance the tolerance to benomyl, one of the most commonly used fungicides in crop protection (Shinohara et al 2013). However, this technology could be applied to other entomopathogenic fungi, such as Beauveria bassiana (Bals.-Criv.)…”

Volatiles from wasabi inhibit entomopathogenic fungi: implications for tritrophic interactions and biological control

“…These conditions should be very suitable for biological control of herbivores using entomopathogenic fungi because high humidity is an absolute requirement for conidial germination and the establishment of infection (Hall 1981;Milner & Lutton 1986;Helyer et al 1992;Luz & Fargues 1999). Furthermore, to avoid downstream water pollution, there are enforced restrictions on chemical applications in wasabi fields; this should also be beneficial for entomopathogenic fungi that can be susceptible to pesticides, particularly fungicides (Saito & Yabuta 1996;Shinohara et al 2013).…”