Morphological and molecular characterization of Alternaria alternata causing Alternaria blight in lentil ( Lens culinaris Medik.) and evaluation of the disease reactions of selected lentil cultivars in Türkiye

Lentil ( Lens culinaris Medik.) is one of the most important edible legumes grown in Türkiye. However, production is increasingly threatened by leaf blight, and Alternaria alternata (Fries) Keissler has emerged as an important causal agent of Alternaria blight. This study aimed to determine the pathogenicity of three A. alternata isolates (NELeAa-1, NELeAa-2, and NELeAa-3) collected between 2023 and 2024 from major lentil-producing provinces in Türkiye, and to evaluate the resistance of eight common lentil varieties (four winter and four summer types). Isolates were identified based on morphological characteristics and dual-locus molecular analyses. To ensure accurate taxonomic identification, in addition to standard Internal Transcribed Spacer (ITS) rDNA sequencing, the species-specific AaltFor/AaltRev primer set was used to target the beta-tubulin ( β -tubulin) gene region. Two-way Analysis of Variance (ANOVA) showed that disease severity was significantly influenced by both the fungal isolate and the host variety ( P < 0.001), with a strong interaction between pathogen virulence and host resistance. Disease severity scores ranged from 15.33% to 71.00%, demonstrating significant variation among cultivars. While the summer varieties ‘Meyveci 2001’ and ‘Karagül’ were the most susceptible (S), winter varieties such as ‘Çiftçi’ and ‘Ceren’ showed a stronger moderately resistant (MR) profile. Isolate NELeAa-2 had the highest virulence, particularly on summer cultivars, whereas NELeAa-1 was more virulent on certain winter-type cultivars. Our findings suggest that utilizing the genetic resistance of winter varieties provides a viable breeding strategy to mitigate Alternaria blight under changing climate conditions.