Diversity and Pathogenicity of Neopestalotiopsis Species Associated with Strawberry Leaf Spot and Fruit Rot in Nova Scotia

We reported the first isolation and characterization of Neopestalotiopsis spp. from symptomatic strawberry plants in Nova Scotia, Canada. Morphological and multilocus sequence analyses confirmed that these isolates were closely related to previously identified aggressive Neopestalotiopsis spp. strains from strawberry and blueberry in the southeastern United States and other countries. Five representative isolates were evaluated for pathogenicity on detached leaves, whole plants, and fruits of multiple strawberry cultivars. The results revealed significant variation in virulence, with isolate NS-1 causing the most severe necrosis across all tissue types. Statistical analysis revealed significant effects of isolate, cultivar, and their interaction on disease severity, indicating differential cultivar responses to the tested isolates. Notably, tissue-specific differences were observed, with some isolates being aggressive on leaves but less virulent on fruit or whole plants, reinforcing the importance of multi-organ phenotyping in resistance screening. Phylogenetic analysis clustered the Nova Scotia isolates within the same clade as Neopestalotiopsis isolate 17–43 L from strawberry and isolates from blueberry, suggesting a potential epidemiological link. The shared nursery propagation system of strawberries and blueberries raises the risk of cross-infection, posing a substantial challenge to disease management strategies in both crops. Collectively, these findings underscore the urgent need for continued surveillance, population-level pathogen analysis, and the development of resistant cultivars to mitigate the spread of this emerging and rapidly evolving pathogen.