Natural occurrence of mycotoxins and toxigenic capacity of Altemaria strains from mouldy peppers

Sweet pepper (Capsicum annuum) is an important crop cultivated worldwide, with Argentina being one of the major producers in South America. The fruit is susceptible to several fungal diseases, leading to severe economic losses for producers. In this study, Alternaria was found as the prevalent genus in mouldy peppers (50% fruits infected). Morphological identification revealed that all 64 Altemaria isolates belonged to small-spored species, most of them corresponding to A. tenuissima, A. arborescens and A. altemata species-groups. Their secondary metabolite profile was evaluated in vitro; altemariols were synthesized by most of the isolates (91% for alternariol and 92% for alternariol monomethyl ether). A high number of Altemaria spp. also produced tenuazonic acid (64%), altenuene (84%) and tentoxin (72%). In addition, damaged pepper fruits were analysed for the presence of tenuazonic acid and alternariols. A total 32 out of 48 spoiled pepper fruits were contaminated with at least one of these metabolites. Half of the samples were positive for tenuazonic acid (range 8-11,422 mu g/kg), while alternariol and its monomethyl ether were less frequently detected (21 and 29%, respectively) and at lower concentrations. This is the first report on the natural occurrence of Ake/nada mycotoxins in Argentinean sweet pepper, and highlights a consumer risk when mouldy fruits are used in industrialized products because these kcompounds are not destroyed by conventional heat treatments. (C) 2016 Elsevier B.V. All rights reserved.