The effect of heat stress on some main spike traits in 12 wheat cultivars at anthesis and mid-grain filling stage

High temperature decreases winter wheat grain yield by reducing the grain number and grain weight. The effect of heat stress on spike grain distribution and weight of individual grains within spike and spikelets was less studied. Our aim is to identify influence of high temperatures during different phenological stages on spike grain distribution and weight and to explore genotypic variation of the studied wheat cultivars. Within this study, a controlled experiment was conducted with 12 different winter wheat cultivars under heat stress at anthesis and mid-grain filling stage. The results showed that spike grain weight, thousand-grain weight and grain number per spike decreased moderately in treatments with individual heat stress at anthesis and mid-grain filling period, respectively, which decreased severely in the multiple heat stressed plants at both stages compared with the control treatment. Heat stress decreased number of spikelets with grains. Grain weight at the G1, G2 and G3 positions had a positive relationship with spike grain weight. Among the studied Serbian wheat cultivars Subotičanka and Renesansa were identified as the most heat tolerant and sensitive, respectively. Heat tolerance of the studied cultivars should be based on the cultivar capacity to retain higher grain weight, and to maintain production of distal spikelet grains.