Integrative characterization of maize-associated Curvularia isolates linking pathogenicity, toxin production and...

Leaf spot disease caused by species of the genus Curvularia is an emerging constraint to maize production under warm agro-climatic conditions. However, integrated analyses linking taxonomy, virulence determinants, toxin production, and metabolomic diversity of regional Curvularia populations remain limited. In this study, fifteen Curvularia isolates associated with maize leaf spot in southern Rajasthan, India, were characterized using a polyphasic approach combining morphology, multilocus phylogeny (ITS, GAPDH, TEF1), pathogenicity assays, extracellular enzyme profiling, quantitative HPLC, and LC-HRMS-based metabolomics. All isolates were pathogenic, but virulence varied significantly (p ≤ 0.05). Isolates MZ4, MZ9, and MZ11 exhibited high Disease Severity Index (DSI > 75%) and produced significantly greater extracellular enzyme activities (amylase, cellulase, lipase, and pectinase). Quantitative HPLC confirmed the presence of methyl-5-hydroxyfuran-2-carboxylate (M5HF2C) in all isolates, with the highest concentrations recorded in the most virulent strains. LC-HRMS profiling of these isolates revealed diverse and largely isolate-specific secondary metabolite signatures, with limited overlap among them. Principal component analysis explained 80.1% of total variance and clearly associated virulence with toxin production and enzymatic activity. Overall, this integrative study demonstrates a strong link between phylogenetic identity, metabolic specialization, and pathogenic variability in Curvularia spp., providing mechanistic insight into maize leaf spot development and supporting targeted disease management strategies.