Two oat genotypes with different field resistance to Fusarium head blight respond similarly to the infection at spikelet level

Cultivar resistance is essential for the management of Fusarium head blight (FHB) disease in oat production. However, the breeders lack methods suitable for phenotyping disease resistance and resistance sources. In this paper we compared two oat genotypes, a rejected variety BOR31 and a landrace VIR7766, with four different traits that could reflect resistance to FHB in a greenhouse environment. Spray and point inoculations were used to inoculate Fusarium graminearum into flowering oat plants. When spray-inoculated, VIR7766 was significantly more resistant against the initial infection than BOR31, measured by the number of Fusarium- infected kernels and by DON accumulation. In the point-inoculated oats, the loss of fresh weight in the inoculated spikelet correlated well with the increasing F. graminearum biomass in the spikelet, measured six days after inoculation. However, no difference in the growth of the fungus was observed between the tested oat genotypes by point inoculation. We speculate that once the infection is established, the ability of the oat plant to resist the spread of the infection within a spikelet is low in the genotypes studied, although oat, in general, due to its panicle structure, is considered to have a high resistance against Fusarium infection.