E-gene cluster architecture as a factor determining photoperiodic response in soybean

Study objective. This study aims to analyze the effects of extreme photoperiods on the growth, maintenance, and productivity of soybean varieties (Glycine max L.) with different allelic variants of the photoperiod sensitivity genes E1, E2, E3, and E4. Materials and methods.The study subjects were 50 soybean varieties (Glycine max (L.) Merr.), differing in the allelic composition of their E genes (E1–E4) and belonging to different maturity groups (from ultra-early to mid-season). The sample included domestic and foreign varieties, including those adapted to northern latitudes and conditions. Phenological observations were conducted daily, recording the date of first flower emergence. At the end of the growing season, morphometric parameters, DNA regulation, PCR analysis, and statistical processing of the obtained results were analyzed. Results. Photoperiod response was shown to be a digital trait, the expression of which is determined by a combination of alleles at the E loci. The presence of dominant alleles E1, E3, and E4 was found to delay flowering by 20—22 days under long days (22 hours) compared to the shortest day (8 hours). Currently, molecular labeling methods are used to identify photoperiod-insensitive varieties (Lancetnaya, Sibirada, Saltus, Chera, Lumaria), in which flowering time is independent of photoperiod. Most of these varieties carry the detected recessive alleles e1-nl/e3-fs/e4-kes, which lead to the loss of function of key genes. Cluster analysis of Δ-changes in productivity revealed two groups of varieties: those with stable productivity regardless of photoperiod and those with a pronounced photoperiod response. Conclusion. Based on the results, selective breeding strategies for different latitudinal zones are proposed. The effectiveness of using an extra-long day (18—22 hours) as a rapid test for identifying progressive lines with recessive E-gene alleles in the early stages of breeding is demonstrated. The obtained data are important for expanding the range of soybean cultivation in high-latitude regions.