Pyramiding of Xa23 and bph20 (t) genes in rice varieties using molecular marker-assisted selection.

[Objective]The present experiment was conducted to explore molecular marker-assisted selection for pyramiding Xa23 and bph20 (t) genes in order to get multiple resistant homozygous rice varieties and to provide genetic resources for breeding high yielding and multiple resistant rice varieties. [Method]In addition to hybridization, backcross and traditional field selection methods, molecular markers have been used to identify two-resistant genes, viz., Xa23 and bph20(t) and their pyramiding in homozygous rice strain. [Result]Xa23-linked EST Marker C189 showed highly stable and specific amplification and it may be used as a breeding marker. Marker BYL7 did not showed the expected results and the bands amplified using this were not stable. There is need to develop a more specific marker in order to make use of bph20(t). However, after the pyramiding of genes using MAS and breeding methods, rice stains having 16 Xa23 and bph20(t) were obtained in the BC2F2 groups. [Conclusion]Using Xa23-linked EST Marker C189 and bph20(t)-linked Marker BYL7, we have successfully selected some genotypes in BC2F2 group having two resistant genes pyramided together. The studies demonstrated that marker-assisted selection is a simple and effective tool to breed new multiple-resistant rice varieties.