Efficacy of Three Entomopathogenic Fungi Beauveria bassiana, Metarhizium anisopliae and Lecanicillium lecanii Isolates against Black Bean Aphid, Aphis fabae (Scop.) (Hemiptera: Aphididae) on Faba bean (Vicia faba L.)

Abstract

Background: A laboratory bioassay study was conducted to evaluate the in vitro pathogenicity of different isolates of B. bassiana, M. anisopliae and L. lecanii, against the adults of black bean aphid. Methods: The PCR-based method was used to identify the different isolates molecularly using sequence information from the ITS region. The total genomic DNA of the 19 fungal isolates was recovered from aphid cadavers using CTAB. The amplified DNA using QRT-PCR showed no significant differences in the ANOVA that tested mean cycle threshold (CT) values from the control. Post-molecular identification of the isolated entomopathogen was approved. The single discriminative concentration bioassay was carried out to determine LT50 values for each of twelve isolates to determine the most virulent for further studies. Result: LT50 values for B. bassiana, M. anisopliae and V. lecanii isolates varied from 110-113, 71-75 and 64-77 h, respectively. B. bassiana isolate BBK2, M. anisopliae isolate MAA2 and V. lecanii isolates VLJ2 were selected for further experiments based on their discriminating concentration values. LC50 of BBA post-exposure to isolates of V. lecanii, M. anisopliae and B. bassiana was 46, 269 and 251 ppm, respectively. A significant difference in cumulative mortality was recorded between the three EPF. M. anisopliae showed a higher significant cumulative mortality during the first and second days post-application. Then V. lecanii recorded higher significant cumulative mortality from the third until the seventh-day post-application. V. lecanii showed higher virulence among the other entomopathogenic isolates.