The exogenous regulation of a phenotypic manifestation of a trait of a photoperiodic sensitivity in soybean

Soybean is a photoperiodically highly sensitive, short-day plant. There are practically no genes and gene complexes of photoperiodic neutrality in the soybean gene pool. This greatly limits the optimal day lengths and latitudinal ranges of cultivation of the vast majority of soybean varieties. Therefore, the task of neutralizing the negative impact of suboptimal, first of all, shortened day lengths on soybeans is of global importance. The purpose of these studies was to study the possibility of exogenous neutralization of photoperiodic sensitivity of soybeans by using gibberellin solutions on vegetative plants in order to prolong the period of their vegetative growth, the formation of additional nodes of beans and seeds, providing an increase in yield against the background of suboptimal, shortened day lengths. The research was carried out in 2019–2022 at the V.S. Pustovoit All-Russian Research Institute of Oil Crops (VNIIMK), Krasnodar, on soybean varieties Puma, Barguzin, Vita and Slavia. Based on the theory of hormonal regulation of flowering by M.H. Chil-akhyan we developed a method for exogenous regu-lation of a genetically determined trait of high photoperiodic sensitivity of soybeans to shortened day lengths. The most sensitive to exogenous regulation of photoperiodic sensitivity stage of soybean ontogeny – the 4th trifoliate leaf (ontogeny stage V4) was established by treating plants with a solution of gibberellin. The most active concentration of gibberellin aqueous solutions was determined – 0.003%, the application of which to soybean leaves, at the stage of ontogenesis V4, causes prolongation of vegetative plant growth, formation of additional nodes, beans and seeds. Exogenous phytohormonal prolongation of vegetative growth increases the yield of photoperiodically sensitive soybean varieties when they are grown under conditions of shortened day lengths, including in second summer crops after harvesting winter crops.