Abstract
Pooja and Naveen are popular semidwarf rice varieties of eastern and northeastern India. Bacterial blight disease caused by Xanthomonas oryzae pv. oryzae (Xoo) and lodging lead to yield loss in both genotypes. Considering unique racial composition of Xoo in target regions, five resistance genes (Xa4, xa5, Xa7, xa13 and Xa21) were pyramided in Naveen using IRBB66 as donor. The near isogenic lines (NILs) showed resistant reaction across growing seasons and against multiple Xoo strains. Although plant height of the NILs were similar to Naveen, several tall and semi-tall recombinants appeared from F(2) generation onwards. Molecular profiling confirmed presence of SD1 allele in Naveen, its NILs and the taller recombinant inbred lines (RILs). Xa4 gene improved lodging resistance in both semidwarf NILs and the taller RILs. One non-lodging semi-tall RIL with Xa4 + xa5 + Xa7 + xa13 + Xa21 + SD1 allelic combination with substantially higher yield than both parents and significantly higher yield than check genotypes was released as a new variety CR Dhan 326 after blind multilocation trials. The Xa4 gene also reduced lodging of SD1SD1 RILs developed by crossing CR Dhan 326 with RP-Bio-226 (xa5 + xa13 + Xa21 + sd1). NILs with Xa4 + xa5 + Xa7 + xa13 + Xa21 genes were also developed in Pooja. However, backcrossing led to irreversible loss of semi-dwarfism and presence of SD1 allele was confirmed in Pooja and its NILs. Semidwarf NILs could be developed only after introgression of sd1 allele. The Xa4 gene reduced plant height of both semidwarf and tall NILs. The non-lodging SD1 + Xa4 NILs of Pooja may suit in semi-deep-water ecology, whereas sd1 + Xa4 NILs are suitable for shallow lowlands. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11032-026-01633-0.