Abstract
BackgroundPresence of Kunitz trypsin inhibitor (KTI) in soybean seeds necessitates pre-heat treatment of the soy-flour for its inactivation before using it in food and feed products. The heat treatment not only enhances processing costs of the soy-based foods and feeds but also affects seed-protein quality and solubility. Genetic elimination of KTI is an important and effective approach. Therefore, molecular marker-assisted backcross breeding (MABB) approach was adopted for genetic elimination of KTI from two popular soybean genotypes, DS9712 and DS9814. PI542044, an exotic germplasm line was used as donor of the kti allele which inhibits functional KTI peptide production.ResultsForeground selection for the kti allele was performed with three closely linked SSR markers while background selection was done with 93 polymorphic SSR markers. Plants in the BC1F1 generation were found to recover 70.4–87.63 % and 60.26–73.78 % of the recurrent parent genome (RPG) of DS9712 and DS9814, respectively. Similarly, selected plants in the BC2F1 generation had 93.01–98.92 % and 83.3–91.67 % recovery of their respective RPGs. Recombinant selection was performed so as to identify plants with minimal linkage drag. Biochemical analysis of the seeds of the selected plants (ktikti) confirmed absence of KTI peptides in the seeds. Phenotypically, the selected plants were comparable to the respective recurrent parent in yield and other traits.ConclusionsMABB approach helped in speedy development of 6 KTI free breeding lines of soybean. Such lines will be suitable for the farmers and the soybean industries to use in production of soy-based foods and feeds without pre-heat treatment of the soy-flour. It would contribute towards wider acceptability of soy-based foods and feeds.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-016-0413-2) contains supplementary material, which is available to authorized users.
Highlights
Presence of Kunitz trypsin inhibitor (KTI) in soybean seeds necessitates pre-heat treatment of the soy-flour for its inactivation before using it in food and feed products
Validation of SSR markers linked to kti Three SSR markers viz., Satt228, Satt409 and Satt429 reported to be linked to kti were tested for polymorphism between the donor (PI542044) and two recurrent parents viz., DS9712 and DS9814
Field evaluation The BC2F2 families of DS9712 and DS9814 containing the null allele of KTI were raised along with the recurrent parents in the fields of ICAR-Indian Agricultural Research Institute, New Delhi during July-October 2013 for assessing the yield and other attributes
Summary
Presence of Kunitz trypsin inhibitor (KTI) in soybean seeds necessitates pre-heat treatment of the soy-flour for its inactivation before using it in food and feed products. Soybean is an important source of high quality oil and protein for both human and animal It cannot be fed raw or unprocessed to the mono-gastric animals due to presence of protease inhibitor called trypsin inhibitor (TI) in its seeds. The Biochemically, KTI is a monomeric and non-glycosylated protein weighing 21.0 kDa, and contains 181 amino acid residues [5]. In soybean, it is encoded by ten independent genes; KTI3 is the most important one, as it predominantly expresses in the seeds [6].
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