The paper presents the study of bread wheat’s chlorophyll content and grain yield traits under changing environmental conditions — optimal water supply and simulated water-deficit conditions. Selecting 15 wheat cultivars from different regions (Russia, Kazakhstan, Kyrgyzstan, Tajikistan, Turkey, and CIMMYT) based on economically valuable characteristics became the specimens for the presented study that evaluated the SPAD indicators in correlation with the grain yield in bread wheat and determined the vital role of genotypes, environments, and genotype by environment interaction effects. The relationship between chlorophyll content and yield parameters under different growing conditions was also well-defined. The results revealed that ecosystems had more influence on the chlorophyll content than the wheat genotypes. Several wheat cultivars with soil moisture tolerance have gained identification, along with the correlation coefficient between chlorophyll content and grain yield under varied environmental conditions of water supply. The study validated the role of genotypes and environments in the manifestation of responses to stress conditions.

Keywords: Bread wheat (Triticum aestivum L.), optimum water supply, water-deficit condition, chlorophyll content index, grain yield, correlation coefficient

Key findings: Climate variability for two years made it possible to determine the wheat genotypes’ potential for resistance to abiotic stress conditions. In the studied cultivars, under the relatively dry season, the chlorophyll content was about the readings of SPAD 250 at 10 units less than in the crop season with high humidity at the early wheat phase. An external factor strongly influenced the chlorophyll content, while the specificity of the cultivars was only 12.7%. The other factors, such as, the volume and pubescence of the leaf and the soil conditions, showed an impact of 15.3%.