Introgression of Multiple Disease Resistant Genes in the Genetic Background of High-Yielding Rice Variety Through Marker-Assisted Backcross Breeding

Abstract

Blast and bacterial blight (BB) are the most dangerous rice diseases. We used marker-assisted backcross breeding (MABB) to pyramid the candidate resistant genes against these diseases, specifically Pi9 and Pb1 for blast, and Xa4, xa13, and Xa21 for BB within the genetic background of BRRI dhan89. We used Pi9-US2 as the donor parent for Pi9, Pb1-US2 for Pb1 and IRBB58 for the Xa4, xa13 and Xa21 resistant genes. For this, triple crosses were made, and F₁ to BC₃F₅ was produced by subsequent backcrossing, selfing and foreground selection. The chi-square evaluation of the phenotyping and genotyping of 300 BC₃F₂ individuals revealed the heredity of blast and BB resistance inherited by the single-gene principle of Mendelian genetics. Finally, we selected the best 23 fixed advance lines (ALs). Among them, 12 lines possessed all these 5 genes (Pi9, Pb1, Xa4, xa13 and Xa21), while 9 ALs consisted of 4 genes. The disease rating of 23 ALs varied from 0 to 3 for both blast and BB diseases, while BRRI dhan89 had a disease rating ranging from 7 to 9. The G5, G6, G19, G4, G2, G11 and G10 ALs exhibited the higher yield ha⁻¹ (8.19, 8.16, 8.14, 8.14, 8.02, 8.02 and 8.01 ton ha⁻¹, respectively) compared to BRRI dhan89 (7.26 ton ha⁻¹). Therefore, gene introgression by MABB could effectively identify and functionally validate the candidate genes with high accuracy to develop a durable, resistant variety in rice breeding programs.