**12. Breeding for reduced trypsin inhibitor**

Soybean germplasm PI542044, also known as Kunitz soybean, contains the null allele of KTI, i.e., kti that encodes a truncated protein and it was developed in a backcross program involving Williams 82 and PI157440 [129]. Introgression of kti is complicated by a number of factors viz., (i) kti being recessive in inheritance, each conventional backcross generation would be requiring selfing followed by estimation of KTI content in the seeds so as to identify a target plant. However, three recessive null alleles, viz. Kunitz trypsin inhibitor, soybean agglutinin, and P34 allergen null were stacked in the background of "Williams 82" and were termed as "Triple Null" [130]. Three SSR markers, viz. Satt228, Satt409, and Satt429 have been reported to be closely linked (0–10 cM) with the null allele of Kunitz trypsin inhibitor [131]. These SSR markers was also validated in the mapping population generated using Indian soybean genotypes as the recipient parent (*TiTi*) and PI542044 (*titi*) as the donor for the null allele [132]. Further, a gene-specific marker has also been designed from the null allele of KTI from genotype PI157440 [15] and has been deployed in the selection of plants carrying the null allele of KTI derived from PI542044 [121]. The null allele of KTI from PI542044 was introgressed into the cultivar "JS97–52" (recurrent parent) through marker-assisted backcrossing using the SSR marker Satt228, tightly linked with a trypsin inhibitor *Ti* locus. An introgressed line JS97–52 with reduced trypsin inhibitor (68.8–83.5%) content was developed [133].
