Effect of Tebuconazole Enantiomers and Environmental Factors on Fumonisin Accumulation and FUM Gene Expression in Fusarium verticillioides.

Fusarium verticillioides is an important corn pathogen that can produce fumonisins (FBs) under certain environmental conditions. In this study, we evaluated the enantioselective impact of tebuconazole enantiomers on the growth and FB production of F. verticillioides on maize-based media at different abiotic factors. The expression of FB biosynthetic genes ( FUM1 and FUM6) was quantified by real-time reverse transcription polymerase chain reaction. The results showed that water activity ( aw), temperature, and types of tebuconazole significantly affected the growth of F. verticillioides. The order of fungicidal activity was (-)-tebuconazole > rac-tebuconazole > (+)-tebuconazole. (-)-tebuconazole exhibited the maximal selective fungicidal activity (242-fold) against F. verticillioides at 0.95 aw and 35 °C. Production of fumonisin B1 (FB1) and fumonisin B2 (FB2) by F. verticillioides was influenced by aw, temperature, types of tebuconazole, and dose. Under most conditions, (-)-tebuconazole showed stronger inhibition for FB1 and FB2 production than (+)-tebuconazole (1.87-2.85-fold reduction in FBs) and rac-tebuconazole. The optimal environmental condition for FB production was at 0.99 aw and 25 °C. Tebuconazole enantiomers differently affected FB biosynthetic gene ( FUM1 and FUM6) expression, but the effects on FB production and gene expression showed no positive correlation. The present study provides a better understanding on ways to minimize FB production in corn treated with fungicides.