The effect of germination conditions on growth of Fusarium graminearum and secretion of deoxynivalenol during floor malting of barley

Abstract

The effect of CO2, temperature, and presence or absence of light on the growth of Fusarium graminearum and secretion of deoxynivalenol (DON) during micro-scale floor malting of CDC Copeland barley was evaluated. DON levels, as quantified by ELISA, ranged from 0.09-1.72 mg/kg. Only temperature (12°C vs. 25°C) and initial fungal load (inoculated vs. non-inoculated) and the interaction between these two variables were significant (p<0.01), where DON increased with temperature and inoculation, but where there was a greater increase in DON with inoculated samples at 25°C than at 12°C. Germinating barley produced CO2 at a rate of 0.009 mg CO2/min per gram at 20°C. To test whether CO2 concentration inside sealed growth chambers could be controlled by a CO2 absorbent, a saturated solution of potassium hydroxide (KOH) was evaluated where surface area and volume were varied. The rate of CO2 absorption increased with increasing surface area and volume of KOH solution. However, the decrease in CO2 was accompanied by decreased relative humidity (RH), which could inhibit barley germination. To examine whether a humectant inside the germination chambers could counteract the dehydrating effect of KOH, a saturated solution of potassium chloride (KCl) was tested. In the presence of KCl, there was a decreased loss of RH inside germination chambers but with the amount of KCl used, a constant RH was not achieved. However, the results suggest that a larger volume, or a different humectant, may be more effective but it was determined that, for the purposes of this study, it was not necessary to pursue this question further.