In 2017-2018, extensive symptoms of sudden decline and fruit rot were observed on date palms in southern Tunisia. Samples of diseased plants were randomly collected in six localities. Based on morphological identification, Fusarium was the most frequent fungal genus detected. A sequencing of translation elongation factor, calmodulin, and second largest subunit of RNA polymerase II genes was used to identify 63 representative Fusarium strains at species level and investigate their phylogenetic relationships. The main species detected was Fusariumproliferatum, and at a much lesser extent, Fusariumbrachygibbosum, Fusariumcaatingaense, Fusariumclavum, Fusariumincarnatum, and Fusariumsolani. Pathogenicity on the DegletNour variety plantlets and the capability to produce mycotoxins were also assessed. All Fusarium species were pathogenic complying Koch's postulates. Fusariumproliferatum strains produced mainly fumonisins (FBs), beauvericin (BEA), and, to a lesser extent, enniatins (ENNs) and moniliformin (MON). All F.brachygibbosum strains produced low levels of BEA, diacetoxyscirpenol, and neosolaniol; two strains produced also T-2 toxin, and a single strain produced HT-2 toxin. Fusariumcaatingaense, F.clavum, F.incarnatum produced only BEA. Fusariumsolani strains produced MON, BEA, and ENNs. This work reports for the first time a comprehensive multidisciplinary study of Fusarium species on date palms, concerning both phytopathological and food safety issues.
Keywords: Fusarium Equiseti Incarnatum species complex; Fusarium brachygibbosum; Fusarium prolferatum; Fusarium solani; fumonisins.