Homeostasis in terms of productive tillering of soft winter wheat varieties, 2021-2023.

The material presents the results of a study on the homeostatic stability and adaptive potential of soft winter wheat (Triticum aestivum L.) varieties of different ecological types (forest-steppe, steppe, and Western European) based on the productive tillering index. The research was conducted during 2021–2023, years characterized by contrasting agroclimatic conditions, which allowed for an objective assessment of genotypic responses to adverse environmental factors. Productive tillering is one of the key components of yield structure, being highly dependent on the variability of weather conditions. The aim of the study was to identify varieties with a high level of homeostasis and the capacity to form a stable number of productive stems. Key aspects of the study: Materials and Methods. A comparative analysis of 12 varieties representing three distinct ecotypes was conducted over the period 2021–2023. Conventional plant breeding approaches were applied to determine the statistical homeostatic index. The homeostatic index (Hom) was calculated mathematically as the ratio of the mean productive tillering value of a given variety to its variability index. This approach enabled a quantitative assessment of each genotype's capacity to maintain stable development under external stress conditions. Results. Analysis of the experimental data revealed substantial varietal and ecotypic differences in the traits examined. Conclusions. Western European ecotype varieties are characterized by high yield potential, yet exhibit considerable contrast in terms of stability levels. Domestic varieties of the forest-steppe and steppe ecotypes generally demonstrate more uniform adaptive performance. Highly stable genotypes — Fidelius, Lisova Pisnia, and Harmonia Odeska — were identified as valuable source material for further breeding programs aimed at enhancing stress tolerance in soft winter wheat. Homeostatic ability (Hom) was calculated according to V. V. Khangildyn and M. A. Lytvynenko (1981): Hom = x² / S, where: Hom – homeostatic ability; x² – the mean value of the studied trait squared; S – standard deviation.