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 Alternaria isolates belonged to small-spored species,
most of them corresponding to A. tenuissima, A. arborescens and A. alternata species-groups. Their secondary metabolite
profile was evaluated in vitro; alternariols were synthesized by most of the isolates (91% for alternariol
and 92% for alternariol monomethyl ether). A high number of Alternaria 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 μg/kg), while
alternariol and itsmonomethyl ether were less frequently detected (21 and 29%, respectively) and at lower concentrations.
This is the first report on the natural occurrence of Alternaria mycotoxins in Argentinean sweet pepper,
and highlights a consumer risk when mouldy fruits are used in industrialized products because these
compounds are not destroyed by conventional heat treatments.