In vitro adventitious root culture system for optimal production of genistein in soybean (Glycine max L. Merrill)

Soybean (Glycine max (L.) Merrill) contains isoflavones, and in particular genistein, which have clinically proven roles. As a result, this bioactive compound is greatly valued in the pharmaceutical industry. Hence, this study was aimed to develop an adventitious root culture system for the production of soy isoflavones (genistein) using hypocotyl explants. In solid culture system, auxin (IAA, 0–57.0 µM; NAA, 0–53.7 µM; and IBA, 0–49.2 µM), media strength (¼x, ½x, ¾x, 1x, and 2x) and in the liquid culture system, IBA (0–49.2 µM), media strength (¼x, ½x, ¾x, 1x, and 2x), and sugars (glucose, fructose, and sucrose) were optimized. After 30 days of culture, IBA at 39.3 µM demonstrated the maximum response in root parameters, with the 1x solid MS medium showing improved root parameters compared to other medium strengths. For liquid system culture optimization, full strength MS medium supplemented with 39.3 µM IBA showed the highest root biomass in liquid medium. Among sucrose concentrations, the highest accumulation of root biomass was observed at 3% (3.87 g flask ^− 1) followed by 4% (3.65 g flask ^− 1), however, 4% sucrose proved favorable for genistein synthesis (9.34 mg g^− 1 DW) compared to 3% (6.29 mg g^− 1 DW). Additionally, the maximum levels of phenolic and flavonoid content were observed at 4% sucrose, correlating with higher antioxidant activities in DPPH and FRAP assays. Gene expression analysis of isoflavone biosynthetic genes revealed higher levels of expression at 4% sucrose compared to the control. These results underscore the crucial role of determining the optimum culture conditions and the effect of sucrose in enhancing root biomass and genistein content in soybean adventitious root cultures.