Isolation and identification of entomopathogenic fungi associated with the spiny bollworm and evaluation of their metabolites against the insect's biological parameters

Document Type : Original Article

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Plant Protection Research Institute, Agricultural Research Centre, Dokki, Giza, Egypt

Abstract

Entomopathogenic fungi (EPF), along with their byproducts such as cuticle-degrading enzymes, serve as robust biological agents for controlling agricultural pests. This study focuses on isolating and identifying fungi found in the spiny bollworm (SBW), Earias insulana larvae cadavers. The investigation delves into the impact of their metabolites on various stages of E. insulana. Among the isolated fungi from the insect larvae cadavers (Trichoderma koning, Fusarium oxysporum, Penicillium notatum, Trichoderma asperellum, and Altarnaria alternata). T. asperellum was the most prevalent, its metabolite displayed substantial larval and pupal mortality rates of 60.73% and 21.82%, respectively.  It also disrupted multiple growth stages of the insects, reducing adult emergence, the number of deposited eggs, and hatchability percentage (68.78, 156.89 and 61.90) compared with control (100.00, 273.11 and 93.17), respectively. Consequently, T. asperellum underwent scrutiny for producing cuticle-degrading enzymes using modified Czapek’s broth medium tailored for each enzyme individually. In each culture filtrate, the activities of proteases and lipases surpassed those of chitinases, potentially explaining the heightened larval mortality rates (70.22 and 68.74%) post-inoculation with proteases and lipases specific culture filtrate, respectively. The verification of T. asperellum's identity was accomplished using the 18S rRNA gene of DNA, and the resulting fungal sequence was deposited into NCBI under accession number OQ616502. The crude filtrate derived from T. asperellum, contains cuticle-degrading enzymes with notably high proteases and lipases activities. This filtrate exhibits potent effects on E. insulana larvae and pupae, significantly impacting their biological processes.

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