Diversity of Pathogenic Fungi Associated with Apples in Cold Storage Facilities in Tunisia

Postharvest storage fungi are major limiting factors for the apple industry. In a study conducted in Tunisia in 2014, six refrigerated fruit storage facilities were surveyed in order to determine disease incidence, identify the pathogenic fungal species on apples and study mycelial growth in vitroand lesion diameters in vivoof sampled fungal isolates. Results showed that Penicillium expansum(42.3%) was the predominant fungus in apples, followed by Alternariaspp. (23%), Botrytisspp. (19.2%), Aspergillusspp. (13.5%) and Fusariumspp. (2%). Isolates collected from storage facilities with highly diverse fungal species had significantly greater mycelial growth at 24°C in vitroand larger lesion diameters on apples and oranges than isolates collected from storage facilities with less diversity. Moreover, a trade-off between the diversity in fungal species and the disease incidence in the storage facilities was suggested; facilities with a low or high disease incidence showed the lowest diversity in fungal species. Controlling disease incidence in cold storage facilities is recommended to limit the diversity in fungal species and the development of virulent isolates. Further studies are needed to determine the fruit storage conditions that influence fungal species diversity and their variability in pathogenicity, in order to implement efficient postharvest disease management.