Relationship between solute and matric potential stress, temperature, growth, and FUM1 gene expression in two Fusarium verticillioides strains from Spain.

The objective of this work was to study the effect of ecophysiological factors on fumonisin gene expression and growth in Fusarium verticillioides. The effects of ionic and nonionic solute water potentials, matric potential, and temperature on in vitro mycelial growth rates and on expression of the FUM1 gene, involved in fumonisin biosynthesis, were examined. FUM1 transcript levels were quantified using a specific real-time reverse transcription-PCR (RT-PCR) protocol. Low temperature and water stress reduced fungal growth. Water stress increased FUM1 transcript levels, especially in the case of stress caused by nonionic solute. The temporal kinetic assays showed that water stress had opposite effects on fungal growth versus FUM1 expression. These results indicate that water stress may be an important factor for fumonisin accumulation, particularly in the later phases of maize colonization when water availability decreases. The quantitative RT-PCR methods described here provide a valuable tool for investigating the ecophysiological basis for fumonisin gene expression and ultimately may lead to more effective control strategies for this important mycotoxigenic pathogen.