Breeding of a Black Soybean Line with Green Cotyledon and Recessive Genotypes for Lectin, KTI, P34, Lipoxygenase, and Stachyose Components

Abstract

Black soybean cultivar with a green cotyledon has long been widely cultivated in Asia due to the high content of health-beneficial anthocyanins and lutein. However, the mature seeds of soybean cultivars with a black seed coat and a green cotyledon contain major anti-nutritional and allergenic components including lectin, Kunitz trypsin inhibitor (KTI), P34, lipoxygenase, and stachyose. Genetically eliminating or reducing the levels of these components might be a method for achieving significantly enhanced quality and nutritional value in the utilization of soybean with a black seed coat and a green cotyledon. The objective of this research is to breed a soybean line with a black seed coat, a green cotyledon, and the penta null genotype (lele-titi-p34p34-lox1lox1lox2lox2 lox3lox3-rs2rs2) for all five components. The ratio for segregation based on the presence or absence of P34 protein was fitted to an expected ratio of 3:1 (χ² = 2.64, α = 0.05) in 146 F₂ seeds. Nine F₂ plants with superior agronomic traits from 28 F₂ seeds with the p34p34 genotype (lacking the P34 protein) were selected and one F₂ plant with the rs2rs2 genotype was finally selected. The penta null genotype for components including lectin, KTI, P34, lipoxygenase, and stachyose was identified in random F₃ seeds and 10 F₃ plants. The characteristics for the selection line included a black seed coat, a green cotyledon, 31.5g in 100 seed weight, and the penta null genotype for five components. The selection line would be bred into a soybean cultivar with a black seed coat, a green cotyledon, and significantly reduced anti-nutritional and allergenic properties. Worldwide, this paper is the first to demonstrate that accumulation of all five recessive alleles for lectin, KTI, P34, lipoxygenase, and stachyose was achieved for soybean with a black seed coat and a green cotyledon.