AUTHOR=Rabaaoui Amal , Masiello Mario , Somma Stefania , Crudo Francesco , Dall’Asta Chiara , Righetti Laura , Susca Antonia , Logrieco Antonio Francesco , Namsi Ahmed , Gdoura Radhouane , Werbrouck Stefaan P. O. , Moretti Antonio 

TITLE=Phylogeny and mycotoxin profiles of pathogenic Alternaria and Curvularia species isolated from date palm in southern Tunisia

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1034658

DOI=10.3389/fmicb.2022.1034658

ISSN=1664-302X

ABSTRACT=<p>Date palm (<italic>Phoenix dactylifera</italic> L.), is a widely cultivated crop across North Africa, with about 300 thousand tons of fruits produced per year, in Tunisia. A wide range of fungal pathogens has been associated with leaf spots of date palm, <italic>Alternaria</italic> species being the most frequently reported. Symptomatic leaves of <italic>Deglet Nour</italic> variety were randomly collected in six localities in Tunisia. We used a polyphasic approach to identify 45 <italic>Alternaria</italic> and five <italic>Curvularia</italic> strains isolated from date palm, confirming their pathogenicity. Sequencing of <italic>allergen Alt-a1</italic>, <italic>glyceraldehyde-3-phosphate dehydrogenase</italic> (<italic>gpd</italic>) and <italic>calmodulin</italic> genes allowed us to group 35 strains in <italic>Alternaria</italic> Section, and 10 strains in <italic>Ulocladioides</italic> section. Based on sequencing analyses of <italic>Internal Transcribed Spacer</italic>, <italic>gpd</italic> and <italic>elongation factor</italic> genomic regions, all <italic>Curvularia</italic> strains were identified as <italic>Curvularia spicifera</italic>. All <italic>Alternaria</italic> and <italic>Curvularia</italic> species tested on date palm plantlets proved to be pathogenic, fulfilling Koch’s postulates. Although no significant differences were observed among the species, the highest mean disease severity index was observed in <italic>A. arborescens</italic>, while the lowest corresponded to <italic>C. spicifera</italic>. The capability of these strains to produce mycotoxins <italic>in vitro</italic> was evaluated. None of the <italic>A. consortialis</italic> strains produced any known <italic>Alternaria</italic> mycotoxin, whereas more than 80% of the strains included in <italic>Alternaria</italic> section <italic>Alternaria</italic> produced variable amounts of multiple mycotoxins such as alternariol, alternariol monomethyl ether, altenuene, tenuazonic acid and tentoxin. <italic>Curvularia spicifera</italic> strains produced detectable traces of fumonisins B. This work reports a first comprehensive multidisciplinary study of mycotoxigenic <italic>Alternaria</italic> species and <italic>C. spicifera</italic> associated with leaf spot disease on date palm.</p>