Winter oilseed rape hybrid productivity under interseasonal climatic variability and different growth regulation strategies

Abstract

Purpose. The study aimed to determine the effects of contrasting autumn–winter weather conditions in 2022–2025 on the morphological status, overwintering success, spring regrowth and yield of three winter oilseed rape hybrids. An additional objective was to assess the effectiveness of growth regulators and to establish the prognostic value of key morphological indicators under different seasonal scenarios. Methods. Field experiments were conducted in the Northern Steppe zone using a randomized block design with four replications on the hybrids Temptation, Sequel and Implement. The dynamics of autumn morphogenesis, overwintering and the intensity of spring regrowth were evaluated under the application of Folicur, Caramba Turbo, Elamik and Retacel. Weather data were obtained from the Synelnykove meteorological station. Statistical processing included one- and multifactor ANOVA, Pearson’s correlation analysis, weather response indices and regression modelling. Results. The autumn hydrothermal regime determined the initial developmental status of the crop: in a favourable season the autumn development index exceeded 110 %, whereas in the drought-affected 2024/25 season it declined to 70–75 %. Under stress, plant biomass decreased to 71 %, and the height of the growth point increased to 118 %, leading to reduced overwintering rates of 58–81 %. Growth regulators increased yield by 0.47–0.65 t/ha, with Folicur providing the most consistent effect. Correlation analysis confirmed the strong prognostic value of autumn plant biomass, collar diameter and the spring regrowth index (r up to 0.83). Among the tested genotypes, the Temptation hybrid showed the highest adaptability and the smallest relative yield decline under severe stress, combining favourable autumn morphology with the strongest spring response indices. The regression model explained 87 % of yield variation. Conclusions. Autumn weather conditions established the boundaries of crop performance, forming initial morphological differences that determined overwintering and spring regrowth capacity. Growth regulators partially mitigated weather-induced stress; however, their effectiveness depended on genotype and seasonal conditions. The most stable productivity was recorded for the hybrid with the best autumn development and the highest spring response index – Temptation.