Secondary metabolite profiles of Alternaria isolates from tomato fruit

MALDONADO HARO, M.L.; NIELSEN, K.F.; PATRIARCA, A.

Conferencia; Mycotoxins and Phycotoxins; 2023

Alternaria is a fungal genus that includes both saprophytic andpathogenic species. As plant pathogens, they cause severe problems inagriculture, reducing crop yields and spoiling fruits during storage. Somespecies are able to produce and accumulate secondary metabolites in the cropsthat can affect human and animal health. At least 70 secondary metabolites havebeen reported for the genus, including mycotoxins with proven toxicity. Thesecondary metabolite profiles of Alternaria species are relevant in understandingtheir role in plant pathogenicity and assessing the health risk forconsumers. Tomato issusceptible to Alternaria infection, and its mycotoxins havebeen detected in fruits and tomato products. The objective of the present workwas to evaluate the secondary metabolite profiles of Alternaria isolatesfrom tomato fruits grown in Argentina. A total of 50 isolates from tomato fruitbelonging to section Alternaria according to their morphological andmolecular identification and four reference strains were included in the study.The isolates were inoculated at three points in DRYES agar and incubated at 25°C for 14 days in darkness. The metabolite profiling was analysed using amicro-scale extraction method modified for Alternaria metabolites(Andersen et al., 2015). UHPLC–DAD-HRMS analysis was performed following themethodology described by Klitgaard et al. (2014).A total of 21 Alternaria secondarymetabolites were confirmed by MS/MS and UV–Vis data, and identical retentionindex to standards when available. Tenuazonic acid was the secondary metabolitemost frequently produced by the tomato isolates (84 %). Other metabolitesdetected in a significant number of cultures were altechromone A (72 %),isopropyl tetramic acid (62 %), dihydrotentoxin (54 %), alternariol (44 %), andtentoxin (42 %). Regarding mycotoxin production, other frequently produced werealternariol monomethyl ether (34 %) and altertoxins (ATXs), with ATX-II (38 %),ATX-III (28 %) in higher frequency than ATX-I (12 %).The chemicalcharacterization of Alternaria isolates from tomato fruits revealed adiverse range of secondary metabolites, including known mycotoxins. Theseresults emphasize the potential health risk associated with Alternaria contaminationin crops and processed food and highlight the importance of understanding theirrole in pathogenicity and toxicity.