Isolation and Characterization of Indigenous Isolates of the Entomopathogenic Fungus Aschersonia placenta Berk.

Abstract

Sap-sucking pests such as whiteflies, mealybugs, aphids, hoppers, thrips, and mites cause significant crop losses. Their management largely depends on chemical pesticides; however, indiscriminate use has resulted in resistance development, pest resurgence, environmental contamination, and related health risks. Entomopathogenic fungi offer a viable alternative for sustainable pest management. Aschersonia placenta (Hypocreales: Clavicipitaceae) is an entomopathogenic fungus that has been identified as a potential biological control agent against sucking pests, specifically whiteflies and scale insects. In the present study, indigenous isolates of A. placenta were obtained from naturally infected insect hosts during field surveys conducted in Thrissur and Ernakulam districts, Kerala. The isolates were characterised using both morphological and molecular approaches, and two isolates were designated as Asch3 and ABF5. Morphological characterization was carried out based on colony features and microscopic structures, while molecular identification involved amplification and sequencing of the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA). Isolates Asch3 and ABF5 exhibited pulvinate, yellowish-white to yellow stroma with a distinct hypothallus and tomentose texture. Morphological identification was supported by yellowish to reddish-orange conidial masses, fusoid conidia (12.83–13.21 × 1.65–1.77 μm), and the development of capilliconidiophores. On potato dextrose agar (PDA), colonies reached 1.75–1.8 cm in diameter after 14 days of incubation. Subsequent BLASTn analysis of the sequences revealed 99% identity with reference sequences of A. placenta archived in the NCBI database. Overall, the study confirms the identity of the indigenous isolates as A. placenta. While their biocontrol potential remains to be evaluated, the identification of these isolates provides a basis for their future application in integrated pest management (IPM) strategies.