Characterization and pathological studies on Curvularia eragrostidis, the causal agent of Curvularia leaf spot disease of white yam in Ghana

Yam leaf spotting diseases are important diseases of yam in the tropics. Mitigation strategies for these diseases are hindered by concerns regarding the variability of the causal agents. This needs to be studied for sustainable management strategies to be developed and employed in seed yam production. In this study, the identities, pathogenicity, and virulence of Curvularia isolates associated with Curvularia leaf spot in 34 seed yam farms were studied in 2021. Isolations were made from 102 diseased yam leaves and isolates belonging to Curvularia species characterized based on morphological (micro and macro) and pathologic characteristics. The Sanger sequencing method was conducted on the isolates to determine their species and genetic relatedness. Isolates of Curvularia spp. were grouped into five morphotypes (denoted as BM-1, BM-2, BM-3, BM-4, and BM-5) based on morphological descriptions. From the molecular analysis, the morphotypes BM-1, BM-2, BM-4, and BM-5 were identified as Curvularia eragrostidis while morphotype BM-3 was Curvularia lunata. All the morphotypes were pathogenic to yam with the exception of BM-3. This study has enhanced knowledge of the diversity of C. eragrostidis which causes Curvularia leaf spot of yam in seed yam production in Ghana. Key words: Curvularia eragrostidis, seed yam, disease management, pathogenicity, virulence, disease severity.