Improvement of bacterial blight and brown planthopper resistance in an elite restorer line Huazhan of Oryza

Development of resistant varieties is one of the most economical and effective strategies to prevent rice from bacterial blight disease (BB) and brown planthopper (BPH), the two main pests jeopardizing rice production. The hybrid rice Tianyouhuazhan (TianfengA/Huazhan) has been widely used in rice production in China, but this hybrid is susceptible to BB and BPH. In this study, one BB resistance gene (Xa23) and two BPH resistance genes (Bph14 and Bph15) were simultaneously introgressed into the restorer line Huazhan to improve the BB and BPH resistance of Tianyouhuazhan using marker-assisted backcrossing (MABC) strategy coupled with phenotypic selection. The results of identification of BB and BPH resistance revealed that almost all of the improved restorer lines and their derived hybrids showed high resistance (HR) or resistance (R) to BB and BPH. Almost all of the agronomic traits of improved restorer lines and their hybrids were similar to those of their respective original versions in field trial, except the 1000-grain weight of improved hybrids showed an extremely significant increase than that of Tianyouhuazhan. Plot yields test in 2013 and 2014 suggested that two improved hybrid combinations named as TianfengA/R43-06 and TianfengA/R43-07 had higher grain yields per plot than Tianyouhuazhan and other improved hybrids. These results clearly indicate that pyramiding of Xa23, Bph14 and Bph15 genes is a useful approach for improving BB and BPH resistance, two hybrid combinations TianfengA/R43-06 and TianfengA/R43-07 could replace Tianyouhuazhan for extension in BB and/or BPH epidemic area in China.