Genetic and molecular characterization of Null KTI allele in backcrossed soybean populations

Abstract

Soybean (Glycine max), a nutrient-rich crop, is valued for its high protein and essential fatty acid content, alongside bioactive compounds beneficial to human health. Despite its advantages, soybean’s anti-nutritional factors, especially Kunitz trypsin inhibitor (KTI) and Bowman-Birk inhibitor (BBI), limit protein digestibility and nutrient absorption, necessitating genetic modifications for improved utilization. This study utilizes marker-assisted backcrossing (MABC) to introduce a null allele for the KTI gene into high-yielding, charcoal rot-resistant soybean genotypes AMS-MB-5-18 and AMS-MB-5-19, with NRC-101 and NRC-127 as donor parents. A BC1F4 population derived from these crosses was analysed to identify lines free of KTI while retaining desirable agronomic traits. Marker-assisted background selection involved 63 SSR markers to monitor recurrent parent genome content (RPGC), analyzed using GGT (v.2.0) software. Results showed a progressive increase in RPGC, reaching an average of 84% in BC1F4 lines, with top plants achieving up to 85.18%. Screening confirmed the successful introgression of the null KTI allele in multiple plants across generations, with 8 plants in the BC1F4 population tested, yielding 5 individuals free of the KTI peptide. These findings demonstrate efficient genomic recovery and anti-nutritional factor reduction in improved soybean lines, advancing their suitability for human consumption and agricultural resilience in Indian soybean breeding programs.