The article presents the research results of preceding crop and growing season conditions influence on protein content variation, wet gluten content of varieties and breeding lines of soft winter wheat (Triticum aestivum L.). The purpose of the research was to establish the variability of flour quality indicators formation, namely protein content (PC) and wet gluten content (WGC) of soft winter wheat varieties and breeding lines depending on preceding crops in years with different hydrothermal conditions in environments of the central part of the Forest-Steppe of Ukraine. The research was conducted during 2020/21-2022/23 at the V.M. Remeslo Myronivka Institute of Wheat of NAAS of Ukraine. The influence of five predecessors on protein content and wet gluten content in flour of 12 genotypes of soft winter wheat was determined. Field, laboratory and statistical research methods were used. It was established that years with different hydrothermal conditions reveal unequal effects on the formation of flour quality indicators. It was found that under arid growing conditions the genotypes of soft winter wheat form a higher protein content and wet gluten content. The unequal influence of preceding crops on the formation of flour quality indicators under different research conditions was noted. Higher quality indicators of flour were determined after soybean as preceding crop (PC = 14.9%, WGC = 32.2%) in 2020/21, after corn (PC = 14.8%, WGC = 32.0%) in 2021/ 22, after green fallow (PC = 11.4%, WGC = 25.5%) in 2022/23. During three years the lowest values of protein content (9.4-11.8%) and wet gluten content (13.2- 24.0%) was noted after sunflower. The most stable genotypes of the influence of the predecessor on the protein content were identified – MIW «Feyeriya», MIW «Vidznaka» and «Lutescens 60400» were the most stable ones, while «Lutescens 60049» and «Lutescens 60302» were the most stable according to both indicators of flour quality. The determining influence for year conditions on flour quality indicators was established (PC – 21.9%, WGC – 35.2%): significant (PC – 17.6%, WGC – 17.0%) – predecessor and essential – interaction of factors year × preceding crop (PC – 17.5%, WGC – 10.4 %) and genotype × year × preceding crop (PC – 12.9%, WGC – 8.7%). The genotype share was 4.3% for protein content and 7.6% for wet gluten content. The genotypes with the most and the least parts of the influence of the studied factors were identified. A reliable strong (r = 0.86) linear relationship between protein content and wet gluten content in varieties and breeding lines of soft winter wheat was determined. The identified influence features of predecessors on the formation of flour quality indicators should be taken into account when growing winter wheat.

Key words: Triticum aestivum L., protein content, wet gluten content, growing season conditions, predecessor, variation coefficient, ANOVA.