Abstract
Understanding the interaction between pathogen virulence and host responses is very important for selecting virulent isolates of entomopathogenic fungi that control an economically important pest, such as the date palm dust mite, Oligonychus afrasiaticus (McGregor). In this study, the virulence of Metarhizium anisopliae (ARSEF 8453 and ARSEF 9374), Beauveria bassiana (ARSEF 6884 and ARSEF 8037), and Isaria fumosorosea (ARSEF 9602 and ARSEF 7284) was evaluated by virulence-regulating traits and host detoxification-related enzymatic analysis. The results revealed significant differences in virulence among all tested isolates of entomopathogenic fungi. The most virulent isolate of B. bassiana ARSEF 6884 (LT50 = 6.3 days; LC50 = 2.7 x 10(6) conidia ml(-1)) observed in the current study revealed the highest activity of cuticle-degrading protease Pr1 (2.12 +/- 0.10 mu mol NA ml(-1) min(-1)) compared with the least virulent isolate of I. fumosorosea ARSEF 7284 (LT50 = 13.1 days; LC50 = 7.9 x 10(7) conidia ml(-1)). Virulent isolates successfully infected the target host and revealed lower activities of antioxidant (catalase and superoxide dismutase) and detoxification (glutathione S-transferases) enzymes at late stage infection. In conclusion, isolates ARSEF 6884 and ARSEF 9374 were found to be promising for the development of an environmentally friendly management strategy to control date palm dust mites.