Resumen
The bacterial blight (BB) disease of rice is a major disease that reduces yield heavily in susceptible varieties. Ranidhan is a late maturing popular rice variety but shows high susceptibility to the disease. Two BB resistance genes were transferred into the variety through a marker-assisted backcross breeding approach. Tightly linked molecular markers were deployed to track the BB resistance genes in the plants carrying the target genes in each backcross generation. Foreground screening detected 17, 16 and 15 progenies to carry the 3 BB resistance genes in BC1F1, BC2F1 and BC3F1 generations, respectively. The selected BC3F1 plant was selfed and three different combinations of BB resistance genes were tracked in homozygous state in seven BC3F2 plants. The pyramided lines carrying three resistance genes in homozygous conditions were evaluated for BB disease resistance by inoculating with eight virulent Xoo strains. Five pyramided lines carrying two resistance gene combinations (Xa21+xa13 and Xa21+xa5) exhibited enhanced resistance against the BB pathogens. The disease resistance was in the order of Xa21+xa5 < Xa21+xa13 < xa13+xa5 gene combinations in conferring the resistance. The developed pyramided lines were similar to the recipient parent for the majority of the important agro-morphologic and grain quality traits.