Pyramiding of blast and bacterial leaf blight resistance genes into rice cultivar RD6 using marker assisted selection

Blast caused by the fungus Magnaporthe oryzae (Hebert) Barr. and bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) are two major diseases of rice (Oryza sativa). The use of varietal resistance is the most appropriate strategy for controlling the diseases, and molecular assisted selection can potentially accelerate breeding programs. The objective of this study was to pyramid genes conferring resistance to blast and bacterial leaf blight diseases to rice cultivar RD6, using molecular assisted selection. Near-isogenic lines (NIL) derived from two blast resistant crosses (RD6 × P0489 and RD6 × Jao Hom Nin) were pyramided with IR62266 (xa5), to transfer bacterial leaf blight resistance to RD6 introgression lines. Five flanking sets of simple sequence repeat (SSR) markers (RM319/RM212, RM48/RM207, RM224/RM144, RM313/RM277 and RM122/RM159: four for blast and one for BLB resistance) were used for screening of introgression lines carrying five quantitative trait loci (QTLs) from the BC1F2 generation through to BC2F2:3 generation, and 12 pyramiding lines were identified. Gene validation for blast and bacterial leaf blight diseases was accomplished using artificial inoculation under greenhouse conditions. BC2F2:3 2-8-2-24 and BC2F2:3 2-8-2-25 showed greater levels of blast broad spectrum resistance (BSR) whereas BC2F2:3 2-8-2-36 expressed the highest of bacterial leaf blight resistance with a high blast BSR. Keywords: Gene pyramiding, introgression lines, molecular marker, Near-isogenic lines, SSR. African Journal of Biotechnology Vol. 12(28), pp. 4432-4438