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Heat stress around anthesis is considered to have an increasing impact on wheat yield under the ongoing climate change. However, the effect of high temperatures and their duration on formation of individual yield parameters is still little understood. Within this study, the effect of high temperatures applied during anthesis for 3 and 7 days on yield formation parameters was analysed. The study was conducted in growth chambers under four temperature regimes (daily temperature maxima 26, 32, 35 and 38°C). In the periods preceding and following heat stress regimes the plants were cultivated under ambient weather conditions. The number of grains per spike was reduced under temperatures ≥ 35°C in cv. Bohemia and ≥ 38°C in cv. Tobak. This resulted in a similar response of spike productivity. Thousand grain weight showed no response to temperature regime in cv. Tobak, whereas in cv. Bohemia, a peak response to temperature with maximum at 35°C was observed. The duration of heat stress had only little effect on most yield formation parameters.

To ensure the selection of wheat genotypes that are resilient to future climatic conditions, with drought already being the most significant and acute problem in many areas, twenty winter wheat cultivars were tested for drought stress tolerance from the beginning of stem elongation (DC 30; Zadoks decimal codes) for 49 days (until the stage of grain development, DC 73–75) within an automatic phenotyping platform. The control plants were regularly irrigated to 70% of soil water capacity (SWC), while the drought-stressed plants were subjected to controlled drying until the permanent wilting point (15% of SWC) was reached. Then, the drought-stressed plants were rewatered again to 70% of the maximum SWC. After they recovered, the plants were again exposed to ambient weather conditions. The final yield formation parameters were assessed at the fully ripe stage. Our results showed that the genotypes originating in Western Europe manifested the highest response to the experimentally set drought in the grain number per spike measurement, while the genotypes originating in the warmer regions of southeastern Europe manifested the highest response to the experimental drought mainly in thousand grain weight measurement. Similar response patterns were evident for late- and early-maturing genotypes. The results indicate the potential of selecting genotypes with increased drought resistance even within the existing set of cultivars.