Characterization of mycotoxigenic Alternaria species isolated from the Tunisian halophyte Cakile maritima

Cakile maritima is a typical halophyte of the Mediterranean coasts. In addition to its ecological and industrial properties, C. maritima has antiscorbutic, diureticand purgative roles in folk remedies. This plant is infected by different fungal species,mainly belonging to Alternaria genus. Two-hundred Alternaria strains were collectedfrom four different pedo-climatic areas in Tunisia, from C. maritima fresh plant tissuesshowing symptoms of Alternaria infection. Phylogenetic analyses of 79 representativeAlternaria strains, were carried out using multi-locus gene sequencing. All the strainsclustered in the Alternaria Section: 47 strains had high homology with A. alternata reference strain, 13 grouped with A. arborescens reference strain, 12 grouped with A. malireference strain, and seven strains were not well defined with A. mali as their closestspecies. In vitro production of tenuazonic acid (TA), alternariol (AOH), alternariolmonomethyl ether (AME), and altenuene (ALT) was evaluated. Approx. 68% of strainssimultaneously produced AOH, AME and TA. Only two A. alternata and one A. malistrains were ALT producing. Pathogenicity tests on leaves of C. maritima were carriedout with 41 representative strains. Alternaria arborescens showed the greatest pathogenicity compared to A. alternata and A. mali, although no statistically significant differences in pathogenicity were observed. This is the first study on Tunisian populationsof Alternaria species isolated from the extremophile C. maritima.