Gene Pyramiding for Achieving Enhanced Resistance to Bacterial Blight, Blast, and Sheath Blight Diseases in Rice.

Bacterial blight, blast, and sheath blight are the commonest diseases causing substantial yield loss in rice around the world. Stacking of broad-spectrum resistance genes/QTLs into popular cultivars is becoming a major objective of any disease resistance breeding program. The varieties ASD 16 and ADT 43 are the two popular, high yielding, and widely grown rice cultivars of South India, which are susceptible to bacterial blight (BB), blast, and sheath blight diseases. The present study was carried out to improve the cultivars (ASD 16 and ADT 43) through introgression of bacterial blight (, , and ), blast (), and sheath blight (, , and ) resistance genes/QTLs by MABB (marker-assisted backcross breeding). IRBB60 (, , and ) and Tetep (; , , and ) were used as donors to introgress BB, blast, and sheath blight resistance into the recurrent parents (ASD 16 and ADT 43). Homozygous (BCF generation), three-gene bacterial blight pyramided ( + + ) lines were developed, and these lines were crossed with Tetep to combine blast () and sheath blight (, , and ) resistance. In BCF generation, the improved pyramided lines carrying a total of seven genes/QTLs ( + + + + + + ) were selected through molecular and phenotypic assay, and these were evaluated for resistance against bacterial blight, blast, and sheath blight pathogens under greenhouse conditions. We have selected nine lines in ASD 16 background and 15 lines in ADT 43 background, exhibiting a high degree of resistance to BB, blast, and sheath blight diseases and also possessing phenotypes of recurrent parents. The improved pyramided lines are expected to be used as improved varieties or used as a potential donor in breeding programs. The present study successfully introgressed , and QTLs (, , and ) from Tetep and major effective BB-resistant genes (, , and ) from IRBB60 into the commercial varieties for durable resistance to multiple diseases.