Morphological and genomic characterization of Neofabraea vagabunda strains causing bull’s eye rot in apples

Neofabraea vagabunda is the causal agent of the bull’s eye rot disease in pome fruits. Symptoms only manifest at the postharvest stage, thus posing a particularly challenging threat to postharvest management. However, there is considerable variation among and within fungal isolates in term of ecological and epidemiological behavior. To address these aspects, thirty-one N. vagabunda strains isolated from North-East Italy from 3 apple varieties (Cripps Pink, Fuji, and Morgenduft) were characterized. They exhibited distinct morphological characteristics, suggesting the presence of genetic variation within the species, influenced by environmental factors or host specificity. Three representative isolates were characterized through in vitro and in vivo assays, in different temperature (0–30 °C, step 5 °C) and water activity (aw =0.99, 0.95, 0.90, and 0.85) regimes. Colony morphology, ecological needs and genomic profiles showed relevant differences among strains associated with virulence. Our results provide an integrated overview of N. vagabunda populations in the monitored area and offer quantitative ecological parameters that can support the development of a predictive model and improved postharvest management strategies for bull’s eye rot.