Comparison of environmental profiles for growth and deoxynivalenol production by Fusarium culmorum and F-graminearum on wheat grain

Aims: Comparisons were made of the effect of water activity (a(w) 0.99-0.85), temperature (15 and 25degreesC) and time (40 days) on growth/production of the trichothecene mycotoxin deoxynivalenol (DON) by Fusarium culmorum and Fusarium graminearum on wheat grain. Methods and Results: Studies examined colonization of layers of wheat grain for 40 days. Fusarium culmorum grew optimally at 0.98 a(w) and minimally at 0.90 a(w) at 15 and 25degreesC. Colonization by F. graminearum was optimum at 0.99 a(w) at 25 and 0.98 a(w) at 15degreesC. Overall, temperature, a(w) and their interactions significantly affected growth of both species. Production of DON occurred over a much narrower range (0.995-0.96 a(w)) than that for growth. Optimum DON was produced at 0.97 and 0.99 a(w) at 15 and 25degreesC, respectively, by F. culmorum, and at 0.99 a(w) and 15degreesC and 0.98 a(w) at 25degreesC for F. graminearum. Statistically, one-, two- and three-way interactions were significant for DON production by both species. Conclusions: This suggests that the ecological requirements for growth and mycotoxin production by such species differ considerably. The two-dimensional profiles on grain for DON production by these two species have not been examined in detail before. Significance and Impact of the Study: This type of information is essential for developing climate-based risk models for determining the potential for contamination of cereal grain with this trichothecene mycotoxin. It will also be useful information for monitoring critical control points in prevention of such toxins entering the wheat production chain.