Field evaluation of sensitivity of wheat to high temperature stress near flowering and early grain set

Abstract

A field study was undertaken at the Waite campus, Adelaide in 2009 to assess the effect of heat stress on four wheat genotypes. Wheat plants were exposed to heat at the green anther stage [Zadoks growth stage (ZGS) 57-59; H1] and at 7-10 days after anthesis (ZGS 73-75; H2). The heat treatment was applied on a single day in a purpose-built (1.5 x 0.5 m) transparent heat chamber. The temperature inside the chamber was increased gradually as a step function to a maximum of 350C, which was maintained for 3 h. Thereafter the temperature was allowed to decrease steadily down to the ambient temperature. This one-day heat event caused a significant decrease in individual grain mass (IGM), grain set and grain yield. As compared to the unheated control, exposure to H1 and H2 decreased grain yields by 18 and 19% in Excalibur, by 19 and 22% in Krichauff, by 21 and 26% in Gladius and by 35 and 30% in Janz. There was a strong correlation between wheat grain yield and IGM at maturity (r = 0.70). As compared to the unheated control, heat stress caused only a small reduction in grain set in the floret a (0.3%) and b (2.3%) but there was a significant reduction in grain set in florets c (16.5%) and d (41.4%). The results clearly indicate that a single day heat-stress event during the reproductive development of wheat can cause a significant reduction in grain yield.