| Summary: | Bacterial blight (BB) disease caused by <i>Xanthomonas oryzae</i> pv. <i>oryzae</i> is a major biotic constraint on obtaining higher grain yields in rice. Marker-assisted backcross breeding (MABB) was performed by the pyramiding of <i>Xa4</i>, <i>xa5</i>, <i>xa13</i> and <i>Xa21</i> resistance genes in the popular variety, Ranidhan. A foreground selection in BC<sub>1</sub>F<sub>1</sub>, BC<sub>2</sub>F<sub>1</sub>, and BC<sub>3</sub>F<sub>1</sub> progenies detected all the target genes in 12, 7 and 16 progenies by using the closely linked markers from a population size of 446, 410, and 530, respectively. The BB-positive progenies carrying the target genes with a maximal similarity to the recipient parent was backcrossed in each backcross generation. A total of 1784 BC<sub>3</sub>F<sub>2</sub> seeds were obtained from the best BC<sub>3</sub>F<sub>1</sub> progeny. The screening of the BC<sub>3</sub>F<sub>2</sub> progenies for the four target genes resulted in eight plants carrying all the four target genes. A bioassay of the pyramided lines conferred very high levels of resistance to the predominant isolates of bacterial blight disease. In addition, these pyramided lines were similar to Ranidhan in 16 morpho-quality traits, namely, plant height, filled grains/panicle, panicles/plant, grain length, grain breadth, grain weight, milling, head rice recovery, kernel length after cooking, water uptake, the volume expansion ratio, gel consistency, alkali-spreading value, and the amylose content.
|
|---|