Genetics and Breeding of Soybeans Lacking the Kunitz Trypsin Inhibitor

  • Theodore Hymowitz
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 199)


The major trypsin inhibitor present in soybean [Glycine max (L.) Merrill] seed is the Kunitz trypsin inhibitor or soybean trypsin inhibitor A2 (SBTI-A2). Four forms of SBTI-A2 have been identified in the U.S. soybean germplasm collection. Three of the forms designated Ti a, Ti b, and Ti c are electrophoretically distinguishable from one another by their different Rf values of 0.79, 0.75, and 0.83, respectively. The three forms are inherited as codominant alleles in a multiple allelic series at a single locus. The fourth form which is the absence of SBTI-A2 is found in P.I. 157440 and P.I. 196168. The allele lacking SBTI-A2 is designated ti and is inherited as a simple recessive to the other three SBTI-A2 forms. Ti a is the most common SBTI-A2 allele in the germplasm collection. Ti b primarily is found in Japan and Korea. Ti c is associated with the Tohoku District, Japan. P.I. 157440 and P.I. 196168 are from Korea. Linkage studies revealed that the Ti and Ap loci are linked by 16.2 ± 1.5 map units. Three isolines of soybeans lacking the Kunitz trypsin inhibitor, derived by backcrossing P.I. 157440 to three commercial cultivars (Ti a Ti a), were released to the research community. Results of preliminary feeding trials, with chicks and young pigs, revealed that gain/feed was significantly higher in lines lacking the Kunitz trypsin inhibitor than cultivars containing the inhibitor. However, the gain/feed was lower in both feeds than commercially processed soybean meal.


Soybean Meal Trypsin Inhibitor Seed Protein Soybean Trypsin Inhibitor Trypsin Inhibitor Activity 


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Copyright information

© Plenum Press, New York 1986

Authors and Affiliations

  • Theodore Hymowitz
    • 1
  1. 1.Department of AgronomyUniversity of IllinoisUrbanaUSA

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