Özet:

: The increased use of chemicals in rice farming poses significant issues regarding the emergence of pesticide/fungicide resistance and environmental sustainability concerns. This study was aimed at the genetic improvement of blast, bacterial leaf blight (BB) and gall midge resistance in a popular rice variety CO 51 which already harbours a blast resistance gene Pi54. Efforts were made to pyramid an additional blast resistance gene Pi9 along with two BB resistance genes ( xa13 and Xa21) and two gall midge resistance genes ( Gm1 and Gm4) into an elite rice variety CO 51 to enhance the resistance level to biotic stresses. The superior lines were selected using functional markers conferring resistance to blast (NBS4 and Pi54MAS linked to Pi9 and Pi54 genes, respectively) and BB [( xa13Prom ( xa13) and pTA248 ( Xa21)] and SSR markers linked to Gm1 (RM1328) and Gm4 (RM22550) for phenotypic screening and agronomic evaluation. The genotyping and phenotyping of F 6 and BC 2F 6 progenies of CO 51 X 562-4, for agronomic traits and resistance to BB and blast, identified ten superior progenies in F 6 and five superior progenies in BC 2F 6. The breeding lines harbouring both xa13+ Xa21 exhibited high levels of resistance to BB (score ≤ 1 cm) and Pi9+ Pi54 exhibited strong resistance to blast (score ≤ 2). Identified lines can be evaluated further for varietal improvement or utilised as genetic stocks in breeding programs.

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