Can Current Prominent Kansas Winter Wheat Lines Tolerate Post-Flowering Heat Stress?.

Wheat (Triticum aestivum L.) is the most widely grown crop in Kansas. Post-flowering heat stress is one of the major environmental constraints for wheat production in Kansas. Studies have shown that optimal temperature for grain development of wheat to be approximately 21°C. During the grain-filling stage for wheat in Kansas, it is not uncommon for temperatures to reach 30°C. Scenarios such as these have resulted in lower productivity in Kansas compared to other parts of the US. Thus, the major objectives were to (i) quantify seven prominent Kansas winter wheat varieties response to post-flowering heat stress (ii) explore levels of post-flowering heat stress resilience in ten experimental lines derived from sources with promising levels of heat tolerance. Two field experiments were conducted in 2016 and 2017. To impose heat stress, heat tents were placed over the plants ten days after flowering and remained until maturity. Temporal physiological measurements recorded throughout the grain filling period included: chlorophyll concentration and fluorescence. Yield and yield components were recorded at maturity. Chlorophyll content and photochemical efficiency of PSII showed rapid reduction under heat stress over time compared to control plants indicating early senescence. Cultivar WB-4458 recorded highest percent reduction (26%) in grain yield under heat stress compared to the control, whereas SY Monument recorded the lowest (2%) reduction. Heat stress reduced grain number per spike and thousand grain weight in nearly all the genotypes compared to control. Genetic diversity documented in the ten experimental wheat breeding lines for heat stress response under field conditions will help provide the basis for further improving the heat tolerance in Kansas cultivars to sustain future climatic changes.