Alternaria and Curvularia species occurring in date palm. PHYLOGENY AND MYCOTOXIN PROFILES OF PATHOGENIC ALTERNARIA AND CURVULARIA SPECIES ISOLATED FROM DATE PALM, IN SOUTH TUNISIA

Date palm (Phoenix dactylifera L.), is widely cultivated across North Africa. In Tunisia, with about 300 thousand tons of fruits produced per year, date palm occupies a strategic place in the socio-economic stability of semiarid and arid regions. Several biotic and abiotic factors can compromise date palm cultivation. A wide range of fungal pathogens have been associated to date palm plants showing symptoms of leaf spots. However, Alternaria species are reported as the most frequent pathogens. Samples of symptomatic plant parts of the common Deglet Nour variety were randomly collected in six localities, in Tunisia. Among the fungal strains, we have selected 50 strains that, based on morphological features, were identified at genus level as Alternaria (45 strains) and Curvularia (5 strains). We used phylogeny, analyses of mycotoxin profile and pathogenicity tests, as a polyphasic approach, to obtain the strains identification at species level. Sequencing of allergen-alt-1a, glyceraldeyde3-phosphate dehydrogenase (GPD) and calmodulin genes allowed us to group 35 strains, identified as A. arborescens, A. tenuissima and A. alternata species, in Alternaria Section, and 10 strains, identified as A. consortialis, in Ulocladioides Section. Based on combined Internal Transcribed Spacer, GPD and Elongation factor genomic regions sequencing analyses, all 5 Curvularia strains were identified as Curvularia spicifera.