PHYTOTOXICITY OF FUMONISINS AND TA-TOXIN TO CORN AND TOMATO

The phytotoxic effects of five fumonisin mycotoxins produced by Fusarium moniliforme, i.e., fumonisin A(1) (FA(1)), A(2) (FA(2)), B-1 (FB1), B-2 (FB2), and B-3 (FB3), together with the aminopolyol hydrolysis products of FB1 and FB2(AP(1) and AP(2), respectively) and tricarballylic acid (TCA) were compared with the host-specific phytotoxin TA-toxin (TA) produced by Alternaria alternata f. sp. lycopersici. A leaf assay was performed on detached leaves of the tomato genotypes Asc/Asc (tolerant to TA) and asc/asc (sensitive to TA) at four concentrations (0.1, 1, 10, and 100 mu M) of each toxin. Seedlings of corn cultivars A1849W and PNR 473 and the two tomato genotypes were also used to assay TA, FB1, FB2, and FB3. The fumonisins caused leaf necrosis identical to that caused by TA and FB1, FB2, FB3, and TA caused significantly (P = 0.01) more necrosis compared with the other metabolites tested. Sterile distilled water (control) and TCA caused no necrosis. Significantly (P = 0.01) more necrosis was observed on the asc/asc genotype compared with the Asc/Asc genotype. There was no significant (P > 0.05) difference between necrosis caused by autoclaved metabolites and that caused by nonautoclaved metabolites. The fumonisins caused dose-dependent reductions in shoot and root length and dry mass of corn and tomato seedlings identical to those caused by TA. The results indicated that TA and FB1 are more phytotoxic to seedlings than are FB2 and FB3. The effects of ah four toxins were more pronounced on seedlings of the sensitive tomato genotype asc/asc than on the tolerant genotype Asc/Asc. No significant differences were recorded in the reaction of the two corn cultivars. The structural similarity of the fumonisin B mycotoxins and TA is therefore reflected by their phytotoxicity to detached tomato leaves as well as to corn and tomato seedlings.