Water relations of some Fusarium species from infected wheat ears and grain

The effects of water activity (aw) and temperature on growth of Fusarium avenaceum, F. culmorum, F. poae and F. tricinctum were studied in vitro on wheat extract agar. Optima and minima aw for growth of all species except F. poae were 0.995–0.99 and 0.89–0.90 at optimum temperatures. The optimum aw for growth of F. poae decreased from 0.995 to 0.98 as temperature increased from 25 to 30 °C. At high aw (>0.98) F. culmorum and F. poae grew much faster (6.8 mm day−1) than F. avenaceum and F. tricinctum (4–5 mm day−1), but at lower aw differences were less. Isolates of F. culmorum and F. tricinctum all grew at similar rates but isolates of F. avenaceum differed in growth rate. Growth of all four species was influenced by substrate (wheat, malt extract or potato dextrose agars) at both high and low aw. RESP-9056