Morphological and Molecular Identification of Erysiphe heraclei Causing Powdery Mildew on Umbelliferous Crops

Abstract

Powdery mildew symptoms observed on umbelliferous crops were investigated to determine the causal agent and confirm its identity through integrated morphological and molecular approaches. Field surveys across cultivated Apiaceae crops revealed typical white powdery fungal growth on leaves, petioles, and stems, leading to chlorosis, premature senescence, and reduced photosynthetic activity. Fungal colonies collected from infected tissues were characterized by superficial mycelium, lobed appressoria, and conidia produced in chains, consistent with features of powdery mildew fungi. Microscopic examination supported preliminary identification as Erysiphe heraclei. Pathogenicity tests conducted under controlled greenhouse conditions successfully reproduced characteristic powdery mildew symptoms on healthy host plants, confirming the pathogenic nature of the isolates. Molecular identification using ITS rDNA sequencing validated species-level identity, with isolates showing high similarity to reference sequences of E. heraclei. Phylogenetic analysis placed all isolates within a well-supported clade corresponding to E. heraclei infecting Apiaceae hosts, indicating limited intraspecific variation among regional populations. Minor sequence polymorphisms suggested possible local adaptation and host-associated differentiation. The study confirms E. heraclei as the primary causal agent of powdery mildew in umbelliferous crops in the surveyed region and highlights its epidemiological significance under favorable environmental conditions such as moderate temperature and high humidity. The findings emphasize the importance of accurate pathogen identification for effective disease management and resistance breeding programs. Early diagnosis using molecular tools can aid in timely intervention and reduce yield and quality losses in economically important vegetable crops belonging to the Apiaceae family.