**4. Materials and Methods**

### *4.1. Plant Materials*

The donor parent, IRBB66, contained five resistance genes, *Xa4, xa5, Xa7, xa13* and *Xa21*, which were introgressed from wild species in the background of IR24. IRBB66 was provided as a courtesy by the Genetic Resources Center (GRC) of the International Rice Research Institute (IRRI). The recurrent parent was TNG82, an elite japonica cultivar with low protein content and good grain quality, but susceptible to bacterial blight disease. A cross was made between TNG82 and IRBB66, with F1 plants backcrossed thrice with TNG82 to obtain BC3F1 plants, which were selfed to obtain the BC3F4 progeny. Selection based on foreground, background and agronomic traits were practiced from BC1F1 to BC2F2 as a means of identifying lines similar to the recurrent parent.
