Abstract
Soybean [Glycine max (L.) Merr.] seed is an important dietary source of protein, oil, carbohydrate, isoflavone and other various nutrients for humans and animals. However, there are anti-nutritional factors in the raw mature soybeans. Kunitz trypsin inhibitor (KTI) protein and stachyose are the main anti-nutritional factors in soybean seed. The ${\alpha}^{\prime}$-subunit of ${\beta}$-conglycinin protein exhibit poor nutritional and food processing properties. The genetic removal of the KTI and ${\alpha}^{\prime}$-subunit proteins will improve the nutritional value of the soybean seed. The objective of this research was to develop a new soybean strain with KTI and ${\alpha}^{\prime}$-subunit protein free ($titicgy_1cgy_1$ genotype) and proper agronomic traits. A breeding population was developed from the cross of the Bl-1 and 15G1 parents. A total of 168 $F_2$ seeds from the cross of the BL-1 and 15G1 parents were obtained. The segregation ratios of 9: 3: 3: 1 ($104Ti\_Cgy_{1\_}:\;30Ti\_cgy_1cgy_1:\;21cgy_1cgy_1Ti\_:\;13titicgy_1cgy_1$) between the Ti and $Cgy_1$ genes in the $F_2$ seeds were observed (${\chi}^2=5.12$, P=0.5-0.10). Two $F_4$ plant strains with proper agronomical traits and $titicgy_1cgy_1$ genotype (free of both KTI and ${\alpha}^{\prime}$-subunit protein) were selected and harvested. 2 strains (S1 and S2) had yellow seed coats and hilum. The plant height of the S1 strain was 65 centimeters. The 100-seed weight was 29.2 g. The plant height of the S2 strain was 66 centimeters and 100-seed weight was 26.2 g. The two strains selected in this research will be used to improve the new cultivar that will be free of the KTI and ${\alpha}^{\prime}$-subunit proteins.
