Comparison of Spray and Point Inoculation with Fusarium graminearum to Evaluate FHB Disease in Two Winter Wheat Genotypes Under Temperature Stress

Two near isogenic lines of wheat; Mercia 1 (Rht-B1b) and Mercia 2 (Rht-D1b) were evaluated for Type I and Type II resistance using point or spray inoculation and incubated under controlled environment. The experiment was a complete factorial combination of 2 x 4 x 2 x 4 {2 genotypes, 4 inoculation treatments (spray + Fusarium, spray + SDW, point + Fusarium, point + SDW) x 2 temperatures} and 4 randomised replicates. Wheat spikes were sprayed with a single spore isolate of F. graminearum 4 days after the start of flowering and transferred to controlled environment cabinets set at either 23/15°C or 28/20°C for 14 days and then taken outside to mature. Results reveals that genotype showed no difference in FHB severity in both spray inoculation and point inoculation but the temperature main effect only approached significance (P=0.071) with low temperature increasing FHB severity following point inoculation. High temperature significantly (P<0.001) increased DON concentration in spray inoculation, contrasted the effect in point inoculation. However, the amount of DON per grain showed no significant (P>0.05) effect. Grains per spike was significantly (P<0.011) reduced by 25% following spray when compared with point inoculation, but showed no significant (P>0.05) effect of temperature. On average, Fusarium infection significantly (P<0.001) reduced wheat grain weight by 28% when compared with uninoculated control.