Influence of growth regulators on winter wheat varieties yield and grain quality

Plant growth regulators are important tools for improving the productivity and technological quality of cereal crops under unstable environmental conditions. In winter wheat, triazole-derived compounds may enhance photosynthetic activity, optimize assimilate redistribution, improve grain filling, and contribute to higher and more stable grain yield. In the present study, seeds of five winter wheat varieties (Khvylia Dnipra, MIP Roksolana, Vezha, LG Magirus, and LG Litopys) were treated before sowing with aqueous solutions of two new triazole-type compounds, CA-64 (potassium [1,2,4]triazolo[1,5-c]quinazoline-2-thiolate) and CA-79 (potassium tetrazolo[1,5-c]quin­azoline-5-thiolate), at concentrations of 0.01%, 0.02%, and 0.04%. Seeds were soaked for 24 h, and water-treated seeds served as the control. Field experiments were conducted during 2023–2025 under steppe conditions of the Prydniprovia. The compounds were evaluated for their effects on photosynthetic activity (SPAD and chlorophyll content), grain yield, yield-structure traits, and grain quality parameters, including protein, gluten, glutenin fractions, and gliadins. The results showed a clear concentration-dependent response. The concentrations 0.01% and especially 0.02% stimulated most of the studied traits, whereas 0.04% caused a depressive effect. The transition between stimulation and inhibition occurred within a relatively narrow concentration range, underscoring the critical importance of precise dose selection. Among the two tested compounds, CA-79 should be considered the more promising option, as it produced stronger improvements in photosynthetic activity, grain yield, yield structure, and most grain-quality traits. In nearly all varieties, CA-79 proved to be more effective than CA-64, particularly at 0.02%, producing the highest increases in photosynthetic activity, grain yield, grain weight per main spike, grain weight per plant, and thousand-grain weight. Positive effects on grain quality were also recorded, especially for protein, gluten and HMW glutenins, although quality traits responded less strongly than productivity traits. The strongest positive responses were observed in the varieties LG Magirus, LG Litopys, and MIP Roksolana, while Vezha also reacted positively but somewhat more moderately. The concentration 0.04% was excessive for both compounds and led to reduced physiological and agronomic performance. Thus, CA-79 at 0.02% can be recommended as the most effective option for improving photosynthetic activity, productivity, yield structure, and technological grain quality in winter wheat, whereas CA-64 at 0.02% may be considered a practical alternative. Further research should integrate field-based evaluation with more focused physiological and molecular studies, particularly those addressing biochemical regulation, antioxidant metabolism, assimilate distribution, and the synthesis of storage proteins.