Morphological and Molecular Characterization of Ascochyta rabiei Causing Ascochyta Blight on Chickpea

Abstract

Isolates of Ascochyta rabiei associated with Ascochyta blight on chickpea (Cicer arietinum L.) were characterized through integrated morphological and molecular approaches to confirm pathogen identity and assess genetic variability. Fungal isolates obtained from symptomatic leaf, stem, and pod tissues exhibited typical grey to dark brown colonies with concentric ring patterns and pycnidia formation under laboratory conditions. Conidia were hyaline, cylindrical to oblong, and septate, consistent with diagnostic features of the pathogen. Pathogenicity assays on susceptible chickpea cultivar under controlled conditions reproduced characteristic necrotic lesions, confirming virulence and fulfilling Koch’s postulates. Molecular characterization using ITS rDNA sequencing, supplemented with partial TEF1-α analysis, revealed high sequence similarity with reference Ascochyta rabiei isolates in global databases. Phylogenetic reconstruction grouped all isolates into a well-supported clade with limited intraspecific variation, indicating a relatively conserved population structure across sampling locations. Minor nucleotide polymorphisms suggested emerging diversity possibly driven by agro-climatic adaptation and host selection pressure. Combined morphological and molecular evidence provided robust confirmation of pathogen identity and highlighted the reliability of multilocus sequencing for accurate diagnosis of Ascochyta blight. The study emphasizes the importance of early and precise detection of pathogen populations to support resistance breeding and integrated disease management strategies in chickpea cultivation systems. Continuous monitoring of pathogen variability is recommended to anticipate shifts in virulence and improve long-term crop protection strategies under changing environmental conditions. These findings provide a baseline for regional pathogen surveillance and support the development of durable host resistance strategies and predictive disease modelling frameworks for sustainable chickpea production in diverse agro-ecological zones.