Submitted to: Fungal Genetics Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: March 26, 1995
Publication Date: N/A
Technical Abstract: Wheat head scab caused by Gibberella zeae is a serious problem for wheat growers worldwide. Head scab causes yield losses and contamination of grain with trichothecene mycotoxins that are injurious to human and animal health. Trichothecenes are also potent phytotoxins which suggests that they play a role in plant diseases. It was previously shown that disruption of the Tri5 gene encoding trichodiene synthase blocks trichothecene biosynthesis and reduces virulence of G. zeae on wheat under growth chamber conditions. In this study, conducted under permit from USDA-APHIS, virulence of a G. zeae strain carrying a disrupted Tri5 and virulence of its Tri5+ progenitor were examined under field conditions. Hard red spring wheat cultivars Wheaton and Butte 86 were grown in central Illinois and inoculated at anthesis by injecting individual heads with fungal conidia or water. After one month, heads were harvested and grain was analyzed for yield and quality, and for kernel infection with G. zeae Tri5+ strains and the Tri5- disruptant by fungal strain isolation and PCR. The Tri5- disruptant infected wheat kernels, but was significantly less virulent (P<.05) than the Tri5+ progenitor on both wheat cultivars as measured by kernel number, weight and germinability, and frequency of infected kernels. These results indicate that trichothecene mycotoxins contribute to the ability of G. zeae to cause wheat head scab under field conditions.