Maize Seedling Blight Induced by Fusarium verticillioides: Accumulation of Fumonisin B1 in Leaves without Colonization of the Leaves

Fusarium verticillioides produces fumonisin mycotoxins during the colonization of maize, and fumonisin B-1 (FB1) production is necessary for manifestation of maize seedling blight disease. The objective of this study was to address FB1 mobility and accumulation in seedlings to determine if proximal infection by F. verticillioides is necessary for FB1 accumulation. Taking advantage of an aconidial mutant known to have limited capability for seedling infection, tissue and soil samples were analyzed to compare wild-type F. verticillioides against the mutant. Inoculation with either strain caused accumulation of FB1 in the first and second leaves, but the mutants were unable to colonize aerial tissues. FB1, FB2, and FB3 were detected in the soil and seedling roots, but only FB1 was detected in the leaves of any treatment. These data suggest root infection by F. verticillioides is necessary for accumulation of FB1 in leaves, but the mechanism for accumulation does not require colonization of the leaf.