Pyramiding insect and disease resistance in an elite indica rice cultivar asd16

Pyramiding transgenes of interest is one of the strategies to engineer multiple stress resistance in crop plants. Transgenic plants which stably express different genes can be hybridized to bring these genes together in one plant. Transgenic rice (Oryza sativa L. cv. ASD 16) plants harbouring genes Xa21 (conferring bacterial blight resistance), tlp (conferring resistance to sheath blight), or gna (conferring resistance to brown planthopper) were used in hybridization experiments. Sexual hybridization was carried out in two different gene combinations: Xa21 × gna and tlp × gna. Molecular analyses were carried out to confirm the presence of transgenes. In F₁ generation, lines harbouring either gene in each of the cross-combination were selected and forwarded to F₂ generation. The presence of genes in F₂ generation was confirmed by PCR, Southern blot hybridization, and Western blotting. The F₂ progeneis harbouring Xa21 and gna exhibited resistance against bacterial blight and moderate resistance against brown planthopper. Similarly, the F₂ lines of tlp and gna combination provided resistance against sheath blight and moderate resistance against brown planthopper. The level of resistance observed in pyramided lines for insect or pathogens was comparable to the resistance observed in their parental lines. Our study shows that pyramiding genes by hybridization between transgenic plants could be one of the strategies to develop cultivars with multiple biotic stress resistances.