Improvement of blast resistance of the popular high-yielding, medium slender-grain type, bacterial blight resistant rice variety, Improved Samba Mahsuri by marker-assisted breeding

Improved Samba Mahsuri (ISM) is a popular, high-yielding, bacterial blight resistant rice variety possessing medium-slender grain type. As ISM is highly susceptible to blast disease of rice, through the present study we have transferred two major blast resistance genes, Pi2 and Pi54 into the elite variety by marker-assisted backcross breeding. The two blast resistance genes were transferred to ISM through sets of backcrosses. In every backcross generation, PCR-based markers, specific for the blast resistance genes (Pi2 and Pi54) and bacterial blight resistance genes (Xa21, xa13 and xa5) were utilized for foreground selection, while a set of 144 parental polymorphic SSR markers were used for background selection and backcrossing was carried out until BC2 generation. A solitary BC2F1 plant possessing Pi2 or Pi54 along with Xa21, xa13 and xa5 and > 90% recovery of ISM genome was selected from the two sets of backcrosses were crossed and the intercross F1s (ICF1s) thus obtained were selfed to generate ICF2s. Homozygous ICF2 plants carrying all the five resistance genes were identified through markers and advanced through selfing till ICF5 generation by adopting pedigree method of selection. Three best lines at ICF5, possessing excellent resistance against bacterial blight and blast and closely resembling or superior to ISM in terms of grain quality: yield and agro-morphological traits have been identified and advanced for multi-location trials.