Characterization of mycotoxins produced by two Fusarium species responsible for postharvest rot of banana fruit

Abstract

In an open-air market in southern Italy, we noticed ‘Lady finger’ banana fruit imported from Costa Rica showing a severe rot, whose symptoms consisted of necrotic peel lesions with variable shape and size. Fusarium sacchari and F. proliferatum were consistently isolated from symptomatic fruit. In pathogenicity tests on ‘Lady finger’ banana fruit, F. proliferatum was more virulent than F. sacchari. Quantitative Time-of-Flight Mass Spectrometric analysis of secondary metabolites produced by isolates of these two Fusarium species on three different matrices (banana peel, barley and maize kernels) identified 11 mycotoxins. Seven of them (Fusaproliferin, Fumonisins A₁, Fumonisins A₂ and Fumonisins B₁, Hydrolysed Fumonisin B₁, Fusarin C and Moniliformin) were detected in matrices contaminated by F. proliferatum isolates. Fumonisin A₁ was the prevalent mycotoxin in both maize kernels and banana peel, while Fumonisin A₂ prevailed in barley kernels. Similarly, seven mycotoxins (the cyclic hexadepsipeptides Enniatins B₂, B₃ and B₄, Fumonisins A₁ and B₂, Hydrolysed Fumonisin B₁ and Fusarin C) were detected in matrices contaminated by F. sacchari isolates, but they were only in part the same as those produced by F. proliferatum isolates. Fusarin C prevailed in all three matrices colonized by F. sacchari. Fumonisin A₁ was detected exclusively in maize kernels while Enniatins B₃ and B_4, Fumonisin B₂ and Hydrolysed Fumonisin B₁ were detected exclusively in barley kernels. Overall, F. proliferatum produced a higher amount of mycotoxins than F. sacchari. Moreover, in banana peel both species produced a lower number and amount of mycotoxins than in the other two matrices.