Studies on in vitro growth and pathogenicity of European Fusarium fungi

The effect of temperature on the in vitro growth rates and pathogenicity of a European Fusarium collection consisting of isolates of Fusarium graminearum, F culmorum, E avenaceum, F poae and Microdochium nivale was examined. Irrespective of geographic origin, the optimum temperature for the growth of F graminearum, F culmorum and F poae was 25 degreesC, while that for E avenaceum and M. nivale was 20degreesC. In general, the growth rates of E graminearum, E culmorum and E poae increased between 10 and 25 degreesC and those of E avenaceum and M. nivale increased between 10 and 20 degreesC. Pathogenicity tests were carried out by examining the effect of the five species on the in vitro coleoptile growth rate of wheat seedlings (cv. Falstaff). Irrespective of geographic origin, the temperature at which F avenaceum, F culmorum and F graminearum caused the greatest retardation in coleoptile growth ranges 20-25 degreesC (> 89.3% reduction), whilst for E poae and M. nivale it was 10-15 degreesC (>45.6% retardation), relative to uninoculated control seedlings. In general, F culmorum and F graminearum were the most pathogenic of the five species, causing at least a 69% reduction in coleoptile growth at 10, 15, 20 and 25 degreesC. General linear model analysis (GLIM) showed that species accounted for 51.3-63.4% of the variation in isolate growth and from 19.5% to 44.3% of the variation in in vitro pathogenicity. Country of origin contributed from 22.6% to 51.9% to growth rate variation and from 0.73% to 7.61% to pathogenicity variation. The only significant correlation between in vitro growth and pathogenicity was that observed for M. nivale at 15 degreesC (r = -0.803, P < 0.05).