Bowman-Birk inhibitor in soybean: Genetic variability in relation to total trypsin inhibitor activity and elimination of Kunitz trypsin inhibitor

Bowman-Birk inhibitor (BBI) is a soybean seed serine protease inhibitor whose nutraceutical properties far exceed its anti-nutritional property arising from its trypsin and chymotrypsin inhibitor activity. High BBI soybean genotypes are sought for the commercial preparation of this nutraceutical biomolecule while low BBI content in Kunitz trypsin inhibitor (KTI)-free genetic background is desirable in soymeal manufacturing. In the present investigation, monoclonal antibody assay of 95 soybean genotypes revealed 11fold genetic variation for BBI concentration. The study led to the identification of 3 very high (>20 mg/g defatted soy flour) and 5 very low BBI (< 4 mg/g defatted soy flour) soybean genotypes. Contribution of BBI to total trypsin inhibition activity ranged from 2.2 to 53.5% with average value of 11.6%. Genotypes with varying level of BBI raised consecutively for two years exhibited non-significant (p>0.05) effect of growing year on the trait. BBI content in BC3F2 derived KTI-free lines was at par with the recurrent parent. Low and high BBI content genotypes with diverse genetic background identified in the study may be exploited to develop mapping population to identify genomic regions underlying BBI in soybean.