Optimized In-Vitro direct shoot organogenesis and regeneration protocol for elite soybean [Glycine max (L.) Merrill] genotype PDKV Amba

Soybean (Glycine max) remains one of the most recalcitrant crops for in-vitro regeneration, hindering progress in genetic improvement and biotechnological interventions. This study aimed to refine a high-frequency direct shoot organogenesis protocol for the elite Indian soybean genotype PDKV Amba (AMS 100-39) using cotyledonary node explants. Various concentrations and combinations of plant growth regulators (PGRs) were evaluated across three stages: shoot induction, multiplication, and rooting. Maximum shoot induction (84.0%) was achieved on MS basal medium supplemented with 1.5 mg/L BAP and 1.0 mg/L IAA. For shoot multiplication, Thidiazuron (TDZ) at 0.5 mg/L proved superior, yielding 4.35 shoots per explant. Optimized rhizogenesis was observed on MS medium supplemented with 2.0 mg/L IBA, producing an average of 5.25 roots per explant. This refined protocol provides a robust foundation for future CRISPR/Cas9-mediated genome editing and genetic transformation in elite soybean cultivars.