Enhancing spot blotch resistance in wheat by marker-aided backcross breeding

The cultivar HUW234 is well adapted and widely grown throughout the Eastern Gangetic plains (EGP) of India. However, popular cultivars of EGP are highly susceptible to the spot blotch disease caused by Bipolaris sorokiniana. The production is highly affected, thereby exerting pressure on the livelihood of the poor and marginal farmers of this region. Two parallel backcross programs were conducted to transfer resistance against spot blotch in the susceptible cultivar HUW 234. The two donor parents were Chirya 3 and Ning 8201. One program targeted the locus QSb.bhu-2A, while the second focused on the two loci Qsb.bhu-2A and Qsb. bhu-5B. Foreground selection was achieved using SSR markers linked to the target(s), and background selection was based on a set of well distributed SSRs. Ten resistant BC3F3 selections were made in Chirya 3 x HUW 234 and 15 in the Ning 8201 x HUW 234. Based on background selection marker genotype, the genetic similarity of the selected BC3F3 individuals with the recipient parent reached as high as 94.3 %. The BC3F3 selections and those made in BC3F4 and BC3F5 showed improved spot blotch resistance in the field, and also yielded better than the recipient parent in presence of the disease.