Enhancement of leaf blast resistance in rice cultivar ‘swarna’ by marker assisted backcross breeding

Swarna is most popular indica rice variety cultivated in India. However, Swarna is highly susceptible to blast disease. As genes that confer effective resistance to blast are available along with gene-specific markers, the present study was carried out to introgress a major blast resistance gene, Pi54 into the genetic background of Swarna through marker-assisted backcross breeding. Rice line Tetep possessing Pi54 gene served as the donor. Marker-assisted backcross breeding strategy was used for introgression of the resistance gene into Swarna. This involved two rounds of backcrossing at each backcross generation, foreground selection was carried out using PCR based molecular marker specific for Pi54 (i.e. Pi54 MAS) and background selection was done using a set of 52 parental polymorphic SSR markers spread across the rice genome. At BC2F2, a single plant possessing the targeted gene along with maximum recurrent parent genome recovery (~90.3%; plant ST-15-2-30-85) was selected and advanced further through selfing and pedigree-based selection for morphological traits. At BC2F4, four lines, viz, ST-15-2-30-85-62-9, ST-15-2-30-85-62-57, ST-15-2-30-85-62-72 and ST-15-3-85-62-175 possessing high level of resistance against blast and all the features identical to Swarna were identified.