Title: Two-dimensional environmental profiles of growth and fumonisin production by Fusarium proliferatum on a wheat-based substrate
Abstract: The effect of water activity (a W ; 0.995, 0.99, 0.98, 0.96, 0.94, 0.92, and 0.90), temperature (15, 25, and 30 °C), incubation time (7, 14, 21 and 28 days), and their interactions on mycelial growth and fumonisin production on wheat-based medium by three Fusarium proliferatum strains isolated from wheat in Argentina was evaluated.Maximum growth rates were obtained at the highest a W (0.995) and 30 °C, with growth decreasing as the a W of the medium was reduced.Maximum amounts of total fumonisins (FB 1 , FB 2 and FB 3 ) were produced at 0.99 a W and 25 °C after 21 and 28 days of incubation for 2 strains, and at 15 °C and 0.98 a W after 28 days of incubation for the third strain.The fumonisin concentrations varied considerably depending on the a W and temperature interactions assayed.The studied strains had different fumonisin production profiles.F. proliferatum ITEM 15661 and ITEM 15664 produced FB 1 and FB 2 whereas F. proliferatum ITEM 15654 was able to produce FB 1 , FB 2 and FB 3 .Interestingly, fumonisin production profiles for each particular strain were related to incubation temperatures.Fumonisins were produced from 15 to 30 °C and at a W values of 0.92 to 0.995 after 21 to 28 days of incubation.However at 7 and 14 days of incubation small amounts of fumonisin were produced at a W lower than 0.94.Two-dimensional profiles of a W by temperature interactions were developed from these data to identify areas where conditions indicate a significant risk from fumonisin accumulation on wheat.Temperature and a W conditions that resulted in fumonisin production are those found during wheat grain development (especially milk and dough stages) in the field.This study provides useful base line data on conditions representing a high and a low risk for contamination of wheat by fumonisins which is becoming of greater concern because this cereal is destined mainly for human consumption.