Effect of Spring Biomass Removal on Expression of Agronomic Traits of Winter Wheat

4 Abstract: Climate change due to global warming will affect the prevailing conditions for wheat breeding and production. In order to prepare response strategies to future climate change, it is important to simulate the growth and yield of wheat under various stress conditions like high air temperature and humidity. To expose autumn-sown breeding material to higher temperatures we cut the above ground biomass in spring in order to artificially delay crop development. The objective of this study was to investigate the effect of biomass removal in spring on expression of agronomic traits in a set of 21 winter wheat genotypes from Kazakhstan. Biomass removal at the pre-stem elongation stage delayed crop development and heading dates by almost 10 days and exposed plants at the same stages of growth and development to temperatures on average 2-3°C higher. This exposure to higher temperature resulted in height reduction of almost 30%, biomass reduction and reductions in all spike productivity parameters of 20-40%. The relationships between the spike productivity traits were also affected. The correlation of spike productivity traits with accumulated air temperature and average relative humidity after anthesis was also different under control and biomass removal treatments. All these changes allowed evaluation of the germplasm under two well contrasted environments. Although the majority of genotypes responded uniformly and negatively to biomass removal stress, there were a few that demonstrated good adaptation and superior performance under both treatments. Biomass removal in this experiment created additional stress that can be utilized in germplasm evaluation and selection. The advantage of the method is its simplicity and uniformity of all other conditions except weather. This method may also be well recommended as an easy way to delay crop development especially for extending the period of crossing or for extending the period of exposure to foliar diseases.