The impact of allelic variation in E-genes on total phenolic content and flavonoid accumulation in soybean (Glycine max (L.) Merr.) seeds

Abstract

Aim. To investigate the impact of early-stage photoperiodic induction (V3–V5 stages) n the partitioning of phenolic compounds and flavonoids in mature seeds of soybean near-isogenic lines (NILs) carrying various maturity gene combinations (E1–E3). Methods. Nearly isogenic lines (NILs) of soybean, in which the E-genes are located at different allelic loci, were used. Short-day (ShD) lines – genotypes E1E2E3, E1e2e3 and neutral-day (ND) lines – genotypes e1E2e3, e1e2E3, e1e2e3. Starting from the V3 stage, plants were exposed to either a natural long day (16 h) or an inductive short day (9 h) for 14 days. Total phenolic content (TPC) and flavonoid accumulation were subsequently analyzed in mature seeds. Results. A profound "metabolic memory" effect was observed, where early induction determines the final seed metabolome. ShD lines (with E1) exhibited significantly higher TPC, particularly following the 9-hour induction. In contrast, ND lines showed lower TPC but a significant shift toward flavonoid biosynthesis. The triple-recessive e1e2e3 genotype achieved the highest flavonoid content and a four-fold increase in the flavonoid-to-phenolic ratio compared to the dominant E1E2E3 line. The e1E2e3 genotype demonstrated metabolic stability, maintaining a constant flavonoid share regardless of the initial photoperiod. Conclusions. E-genes act as metabolic gatekeepers: dominant alleles prioritize generalized phenolic accumulation, while recessive alleles trigger specialized flavonoid partitioning. Photoperiodic neutrality is genetically linked to an enriched flavonoid profile in soybean seeds.