Keywords: Vector control, Entomopathogenic fungi, Papaya Ring Spot Virus, LD50 , LT50
Papaya is economically important cultivated fruit crop grown in all tropical countries, having enormous nutritional values. Papaya Ring Spot Virus imposes a significant crop loss in terms of quality and quantity. To encounter the virus vector (Aphis gossypii), indiscriminate use of chemical pesticides creates severe environmental hazards whereas biological control is a perfect alternative to this problem. The objectives of our present study were isolation and characterization of indigenous fungi and their comparative analysis of entomopathogenic fungi against papaya aphid and finding its pathogenicity. Fungal isolates collected from natural sources were characterized and identified by the cultural and morphological study. Potential EPF genera were molecularly identified by PCR (ITS1-5.8S-ITS2) method. Entomopathogenic fungi were screened against A. gossypii for their pathogenecity by incised leaf disc method. LD50 (median lethal dose) and LT50 (median lethal time) were analyzed by regression analysis. Phylogenetic relationship among EPF was evaluated by MEGA software. Out of forty isolated entomopathogenic fungi, three (Beauveria bassiana deb4, Penicillium verrucosum Nlg1, and Fusarium equiseti khr4) were highly effective entomopathogen. The LD50 value of B. bassiana, P. verrucosum and F. equiseti were 1.4 × 104, 9.8 × 104, 1.0 × 106 spores ml−1, and LT50 values were 32.14, 37.5, 32.14 h respectively. Their phylogenetic analysis indicates related closeness on the basis of their conserved internal transcribed spacer region. In conclusion, the indigenous isolated strain of B. bassiana (deb4) has shown highest biocontrol potentiality amongst three indigenous entomopatogenic fungi under lab condition against A. gossypii and can be applied in agrifields.
Authors are thankful to the Principal of Ramakrishna Mission Vivekananda Centenary College (Autonomous), Rahara, Kolkata, for providing the lab facility. The financial support was received from “Department of Science and Technology & Biotechnology (DSTBT)”, Government of West Bengal, India, as major research project (Sanction Number: 820 (Sanc.)/ST/P/S&T/1G-2/2014 dated 5/1/16); authors are also thankful to them.