Grain weight and malting quality in barley as affected by brief periods of increased spike temperature under field conditions

Abstract

High temperature is usually one of the most important stresses during grain filling affecting both yield and quality in barley crops. In the present study, an attempt was made to assess in the field the effects of short periods of high temperature, using transparent boxes covering only the spikes, with thermostatically controlled electric resistance for increasing the temperature. Treatments consisted of 2 malting cultivars and 5 heat treatments of high temperatures (8°C above the environmental temperature for 6 h/day for 5 consecutive days) over different periods during grain filling. Final grain weight was reduced by 2–14%, depending on the timing of heat stress and the genotype. There was a significant increase in grain nitrogen percentage in both cultivars, and grain β-glucans decreased with high temperatures in Logan and were unchanged in Beka. The resulting malt extract was reduced with exposure to high temperatures, depending on the cultivar, implying that even mild heat stress may change malting performance.