Morphological and molecular characterization of indigenous Ampelomyces isolates

Powdery mildew caused by Erysiphe polygoni is a major disease limiting black gram production, and the exploitation of indigenous mycoparasites offers an environmentally sustainable alternative for its management. This study presents the first comprehensive evaluation of native Ampelomyces isolates recovered from multiple powdery mildew hosts in Guntur district of Andhra Pradesh, India, and assesses their diversity and biocontrol potential against E. polygoni. Field surveys conducted during the rabi season of 2024–2025 yielded fourteen indigenous Ampelomyces isolates from powdery mildew-infected black gram, green gram, ridge gourd, sesame, bhendi, cowpea, bitter gourd, and native gooseberry. Natural infection frequency ranged from 16.6% to 50.0%, while the infection index varied between 5.0% and 20.62%, with the highest mycoparasitic incidence recorded in black gram at Lam village. Morphological characterization revealed significant variability in pycnidial shape, pigmentation, dimensions and pycnidiospore morphology among the isolates, indicating substantial phenotypic diversity. Detached-leaf bioassays demonstrated marked differences in antagonistic activity, with isolate AQBG1 exhibiting the highest mycoparasitic efficacy by producing more than 50% pycnidial coverage on E. polygoni colonies six days after inoculation. PCR amplification using Ampelomyces-specific primers confirmed all isolates, while ITS sequence analysis and phylogenetic reconstruction identified the most effective isolate (AQBG1) as Ampelomyces quisqualis. The recovery of genetically confirmed indigenous Ampelomyces isolates from diverse powdery mildew hosts and the identification of a highly effective native A. quisqualis isolate highlight the local biodiversity of mycoparasites and demonstrate their potential as locally adapted biological control agents for sustainable management of powdery mildew diseases.