Marker-Assisted Pyramiding of Genes Conferring Resistance Against Bacterial Blight and Blast Diseases into Indian Rice Variety MTU1010

Two major bacterial blight (BB) resistance genes (Xa21 and xa13) and a major gene for blast resistance (Pi54) were introgressed into an Indian rice variety MTU1010 through marker-assisted backcross breeding. Improved Samba Mahsuri (possessing Xa21 and xa13) and NLR145 (possessing Pi54) were used as donor parents. Marker-assisted backcrossing was continued till BC2 generation wherein PCR based functional markers specific for the resistance genes were used for foreground selection and a set of parental polymorphic microsatellite markers were used for background selection at each stage of backcrossing. Selected BC2F1 plants from both crosses, having the highest recoveries of MTU1010 genome (90% and 92%, respectively), were intercrossed to obtain intercross F1 (ICF1) plants, which were then selfed to generate 880 ICF2 plants possessing different combinations of the BB and blast resistance genes. Among the ICF2 plants, seven triple homozygous plants (xa13xa13Xa21Xa21Pi54Pi54) with recurrent parent genome recovery ranging from 82% to 92% were identified. All the seven ICF2 plants showed high resistance against the bacterial blight disease with a lesion lengths of only 0.53–2.28 cm, 1%–5% disease leaf areas and disease scoring values of ‘1’ or ‘3’. The seven ICF2 plants were selfed to generate ICF3, which were then screened for blast resistance, and all were observed to be highly resistant to the diseases. Several ICF3 lines possessing high level of resistance against BB and blast, coupled with yield, grain quality and plant type on par with MTU1010 were identified and advanced for further selection and evaluation.