Abstract
BackgroundEntomopathogenic fungi (EPF) attack a wide range of insects. They are considered environmental friendly alternatives to synthetic insecticides for pest control. In the present study, virulence of a native isolate of the EPF, Beauveria bassiana Vuillemin (Hypocreales: Cordycipitaceae) was evaluated against the least mulberry pyralid, Glyphodes pyloalis Walker (Lepidoptera: Crambidae), through bioassay, pathogenic pathways, and immune responses.ResultsThe values of 2.6 × 104 conidia/ml and 3.54 days were determined as the median lethal concentration (LC50) and median lethal concentration (LT50) of AM-118 against the 4th instar larvae of G. pyloalis, respectively. The activities of proteases and chitinases in the culture medium containing the larval cuticle were higher than the control medium. Moreover, the total and the differential hemocyte counts of the larvae were significantly changed after injection with AM-118 spores. The highest numbers of total hemocytes and granulocytes were obtained 3 and 6 h post-injection, while the highest numbers of plasmatocytes and nodules were observed 6 h post-injection. The highest activity of phenoloxidase was determined 12 h post-injection by AM-118 spores.ConclusionsThe findings imply on virulence of the AM-118 isolate against the larvae of G. pyoalis although immune responses were triggered by the spores.
Highlights
Entomopathogenic fungi (EPF) attack a wide range of insects
Several researches have studied the effects of entomopathogenic fungi (EPF) especially, Beauveria bassiana Vuillemin (Hypocreales: Cordycipitaceae) isolates against many lepidopteran insect pests
Before any suggestion for field application, it is necessary to understand the infection mechanism of EPF on the specific insect; the aims of the present research were to (a) bioassay the virulence of a native isolate of B. bassiana against the larvae of G. pyloalis, (b) evaluate the production of extracellular enzymes in presence of the host cuticle to find correlation between secretion of these compounds and virulence, and (c) evaluate the immune responses in the hemolymph of the larvae encountering the spores of B. bassiana
Summary
Entomopathogenic fungi (EPF) attack a wide range of insects They are considered environmental friendly alternatives to synthetic insecticides for pest control. Virulence of a native isolate of the EPF, Beauveria bassiana Vuillemin (Hypocreales: Cordycipitaceae) was evaluated against the least mulberry pyralid, Glyphodes pyloalis Walker (Lepidoptera: Crambidae), through bioassay, pathogenic pathways, and immune responses. The larvae intensively feed on leaves, fold them, and retain the black feces to lose quality of the leaves for silkworm rearing (Khosravi and Jalali Sendi 2010) Another important case is the capability of transmitting pathogenic diseases to silkworm (Watanabe et al 1988). Several researches have studied the effects of entomopathogenic fungi (EPF) especially, Beauveria bassiana Vuillemin (Hypocreales: Cordycipitaceae) isolates against many lepidopteran insect pests. Produced blastospores led to kill the insect hosts by production of secondary metabolites and consumption of nourishing resources in host bodies (Brownbridge et al 2001)
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