Occurrence and field evaluation of sugarcane genotypes for resistance to ring spot disease in China.

Sugarcane ring spot disease significantly impacts crop yield, necessitating the development of resistant cultivars. This study investigated the pathogenicity, morphology, growth characteristics, and molecular identity of the causal fungal pathogen while assessing the resistance of various sugarcane genotypes. Morphological and molecular analyses identified Curvularia guangxiensis as the primary pathogen. Pathogenicity assays demonstrated that strain FS1 exhibited greater virulence than strain BH1, inducing more severe leaf lesions. FS1 also displayed a higher growth rate on potato dextrose agar (PDA) and triggered earlier symptom onset. A multifactorial analysis of genotype, location, and year revealed significant effects on disease incidence, with broad-sense heritability estimated at 0.7, highlighting substantial genetic and environmental contributions. Cluster analysis categorized sugarcane genotypes into five resistance groups, identifying CP81-1258 and Q202 as highly resistant, while CP88-1762, FN07-2020, and GT94-119 were highly susceptible. These findings provide critical insights for breeding resistant sugarcane cultivars and optimizing disease management strategies.