Heat Stress Response of Wheat Cultivars with Different Ecological Adaptation

In the present study, heat treatment was carried out in five different phenological phases, from the first node detectable (DEV31) growth stage to 20 days after flowering, on four wheat genotypes with very different adaptation strategies. They were grown in a controlled environment in a phytotron chamber and exposed to a night temperature of 20 degrees C and a day temperature of either 30 degrees C, at DEV31, or 35 degrees C at all the later developmental phases, for an interval of 14 days. Plant height, leaf number, number of tillers, grain number and grain weight per main and side spikes, TKW per main and side spikes, length of the main and side spikes, and spikelet number per main and side spikes were recorded. High temperature enhanced the stem growth intensity, plant height and tiller number. In contrast, the length of side spikes, spikelet no./side spike, grain no./main and side spike, grain weight/main and side spike and TKW/main and side spike were significantly decreased. The stress response depended strongly on the developmental phase in which the heat stress was applied. Fleischmann 481 and Soissons showed definitely contrasting tendencies both in grain number and grain weight. In the case of the Plainsman V and Mv Magma pair, the higher heat stress tolerance of Magma compared to Plainsman V was evident also from the grain number and weight of the main spike at each developmental phase.