Fumonisin B1-nonproducing strains of Fusarium verticillioides cause maize (Zea mays) ear infection and ear rot

Fumonisins are polyketide mycotoxins produced by Fusarium verticillioides (synonym F. moniliforme), a major pathogen of maize (Zea mays) worldwide. Most field strains produce high levels of fumonisin B-1 (FB1) and low levels of the less-oxygenated homologues FB2 and FB3, but fumonisin B-1-nonproducing field strains have been obtained by natural variation. To test the role of various fumonisins in pathogenesis on maize under field conditions, one strain producing FB1, FB2, and FB3, one strain producing only FB2, one strain producing only FB3, and one fumonisin-nonproducing strain were applied to ears via the silk channel and on seeds at planting. Disease severity on the harvested ears was evaluated by visible symptoms and by weight percent symptomatic kernels. Fumonisin levels in kernels were determined by high-performance liquid chromatography. The presence of the applied FB1-nonproducing strains in kernels was determined by analysis of recovered strains for fumonisin production and other traits. All three FB1-nonproducing strains were able to infect ears following either silk-channel application or seed application at planting and were as effective as the FB1-producing strain in causing ear rot following silk-channel application. These results indicate that production of FB1, FB2, or FB3 is not required for F. verticillioides to cause maize ear infection and ear rot.