PHYTOTOXICITY OF FUMONISINS AND TA-TOXIN TO CORN AND TOMATO

The phytotoxic effects of five fumonisin mycotoxins produced by Fusari um 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 pr oducts of FB1 and FB2(AP(1) and AP(2), respectively) and tricarballyli c 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 (tol erant 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 A184 9W 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. Steril e 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) differ ence between necrosis caused by autoclaved metabolites and that caused by nonautoclaved metabolites. The fumonisins caused dose-dependent re ductions in shoot and root length and dry mass of corn and tomato seed lings identical to those caused by TA. The results indicated that TA a nd FB1 are more phytotoxic to seedlings than are FB2 and FB3. The effe cts of ah four toxins were more pronounced on seedlings of the sensiti ve tomato genotype asc/asc than on the tolerant genotype Asc/Asc. No s ignificant differences were recorded in the reaction of the two corn c ultivars. The structural similarity of the fumonisin B mycotoxins and TA is therefore reflected by their phytotoxicity to detached tomato le aves as well as to corn and tomato seedlings.