Incorporation of a null allele of Kunitz trypsin inhibitor through molecular backcross breeding in soybean [Glycine max (L.) Merrill]

Trypsin inhibitors being anti-nutritional, are a major deterrent in the utilization of soybean as a human food and animal feed. For the genetic elimination of Kunitz trypsin inhibitor, a dysfunctional null allele (titi) of seed-specific KTI3 gene was transferred from (NRC 101 and NRC 102) to three rust-resistant varieties, Phule Agrani, P. Sangam, and P. Kimya. Null allele-specific titi-420bp and linked Satt409-170bp markers could identify two F₂, single F₃and F₄ each, eleven BC₁, ten BC₂ and three BC₂F₂titi plants with titigenotype among the 131 plants studied. In biochemical assay, the trypsin inhibitor activity in seeds of these plants ranged from 4.03 to 9.67 mg/g¹. Based on both molecular and biochemical studies, it could be concluded that these 28plants were free of Kunitz trypsin inhibitor (kti null).