Effect of temperature on head blight of wheat caused by Fusarium culmorum and F-graminearum

The effect of small temperature differentials (16 vs. 20 degrees C) on the pathogenicity of deoxynivalenol producing single isolates of Fusarium culmorum and F. graminearum and on the fusarium head blight (FHB) response of eight wheat cultivars was examined. Fusarium culmorum inoculation caused greater visual disease symptoms at 20 degrees C than at 16 degrees C, both overall and on an individual cultivar basis (overall AUDPC = 13.5 and 9.6, respectively) (P < 0.05). In contrast, F. graminearum inoculation caused greater overall visual disease symptoms at 16 degrees C than at 20 degrees C, both overall and at the individual cultivar level (overall AUDPC = 12.8 and 10.9, respectively) (P < 0.05). Results showed both F. culmorum and F. graminearum inoculations caused a greater loss in yield at 20 degrees C (54.3 and 46.9% relative 1000-grain weight, respectively) compared with 16 degrees C (73.3 and 66.9% relative 1000-grain weight, respectively) (P < 0.05). Fusarium culmorum-inoculated heads contained similar amounts of fungal DNA at both 16 and 20 degrees C (1.9 and 1.7 ng mg(-1) of plant material, respectively) (not significant), while for F. graminearum inoculation, plants contained higher amounts of fungal DNA at 20 degrees C (2.0 and 1.0 ng mg(-1) of plant material, respectively) (P < 0.05). Overall, there was a significant negative correlation between AUDPC and percentage relative 1000-grain weight at both 16 and 20 degrees C (r = -0.693 and -0.794, respectively, P < 0.01).