Potential of novel growth regulators to improve winter wheat ontogenesis

Abstract

Despite their wide practical use, crop responses to specific triazole molecules and doses may differ substantially. Therefore, defining the limits of response variability in promising crops is necessary to justify practical adoption and to formulate sound recommendations. Purpose. The study aimed to evaluate the potential of three new compounds as plant growth regulators, with emphasis on their ability to enhance winter hardiness, and to assess the feasibility of using these compounds in future crop production programs.Methods: Bread winter wheat grain (1,000 seeds per treatment and per control) was primed pre-sowing by soaking in aqueous solutions of three tri-azole-type substances: CAS-64 (potassium [1,2,4]triazolo[1,5-c]quinazoline-2-thiolate), CAS-79 (potassium tetrazolo[1,5-c]quinazoline-5-thiolate), and CAS-67 (5-(2-aminophenyl)-1H-1,2,4-triazole-3-thiolate), at concentrations of 0.01%, 0.02%, and 0.04%. Soaking lasted 24 h; distilled water served as the control. Overwintering success was assessed visually and by measuring soluble sugars in the tillering node during the critical winter period. Results. The formation of germination, crop status before winter, and final survival was determined primarily by the concentration of the applied triazole compounds, whereas varietal (genotypic) specificity was expressed mainly in the degree of sensitivity to increased doses and in the magnitude of the positive response. For both varieties, a typical dose–response pattern for growth regulators was observed: stimulation at low to moderate concentrations and depression at excessive doses. The variety Spivanka showed higher sensitivity to certain factors. The best option was CAS-79 at 0.02%, which ensured the highest survival (up to a 6.0% increase relative to the control). For CAS-64 at 0.01–0.02%, the improvement was stable but less pronounced. Overall, CAS-64 and CAS-79 at 0.02% were the most effective seed-priming treatments, providing a statistically significant enhancement of winter survival. These physiological shifts were consistent with field indicators of stand quality and overwintering. The CAS-79 0.02% and CAS-64 0.02% treatments, which produced the highest carbohydrate reserves in the tillering node, simultaneously showed better germination and post-winter survival. Findings. CAS-79 at 0.02% is the most effective option for both varieties, providing the greatest increase in survival and the best overall consistency of overwintering indicators. CAS-64 at 0.01–0.02% may be used as an alternative, milder option with a moderate but stable effect. CAS-67 is not recommended for pre-sowing treatment aimed at improving winter hardiness because higher concentrations markedly reduce survival, especially in Spivanka.