Characterization of fungi associated with the decline syndrome of strawberry from organic cultivation in Southern Italy

Severe decline symptoms (reaching 60–80% disease incidence) were recently observed on strawberry plants from organic cultivation in Southern Italy, raising a great concern among growers. Root symptomatic samples from two strawberry fields (Eboli and Caserta) were investigated, and different fungi were isolated. A total of 47 pure fungal cultures were chosen and further characterized. Using classical isolation approaches combined with multi-locus phylogeny based on sequences of two barcodes (ITS and tub2), a complex fungal community associated with strawberry decline was revealed. Within this community, Neopestalotiopsis species [63% and 55% relative abundance (RA)] and Dactylonectria torresensis (13% RA) were mostly isolated, indicating that these can have a critical role in the observed decline symptoms in fields. Other fungi, such as Plectosphaerella plurivora, Globisporangium selvaticum, Chaetomium subglobosum, Acremonium sclerotigenum, Geotrichum sp., Neofusicoccum parvum, and Gnomoniopsis fragariae, were less frequently isolated. Furthermore, some very common strawberry pathogens like Macrophomina phaseolina, Rhizoctonia solani, Fusarium oxysporum, Colletotrichum acutatum, Botrytis cinerea, Alternaria alternata, Biscogniauxia numularia, Mucor hiemalis, and Penicillium brevicopactum were only sporadically isolated, suggesting that they did not play any key part in the observed strawberry decline syndrome in the Campania region. Some other non-root-pathogenic fungi, including Clonostachys rosea, Aureobasidium pullulans, Linnemannia sp., and Bjerkandera adusta, were also found and could be further evaluated for their biocontrol potential against strawberry diseases or as plant growth promoters. Results from this study about the fungal community of strawberries affected by decline provided a foundation for upcoming studies on the assessment of organically cultivated strawberries health status aiming to develop efficient disease management strategies.