Abstract:
Backcross breeding enables breeders to transfer a desired trait from a Genetic Improvement of Kenyan sorghum
variety for drought resistance donor parent, into the favoured genetic background of a recurrent parent. This study
utilised back-cross breeding to transfer stay green quantitative trait locus (QTLs) from the donor parental line E361
into a Kenyan farmer-preferred variety, Ochuti as the recurrent parental line. The parental lines E36-1 has 3 stay
green QTLs, SBI-01, SBI-07 and SBI-10 located at various chromosomes. The transfer of these QTLs was
confirmed with the help of Simple Sequence Repeats (SSRs) molecular markers. Five foreground markers that
were polymorphic among the two parental genotypes were used to identify individuals of F1 generation that had stay
green QTLs transferred into Ochuti. A maximum of two QTLs, namely, SBI-07 and SBI-10 were identified as
having been transferred into three individual genotypes. Two other F1 genotypes had only one QTL (SBI-10)
transferred into Ochuti. The heterozygous F1 genotypes were used as the female parents in the generation of
BC1F1. About 25% of the BC1F1 progenies that were genotyped had at least One QTL introgressed. As is the
case in all marker-assisted back-cross breeding, the rate of success in introgressing QTL from donor to recurrent
parental lines depends on the number of plants screened.