**5. Conclusions**

The use of marker-assisted selection in backcross breeding is an effective and reliable approach for pyramiding BB-resistant genes in rice. In this study, the pyramiding lines that possess resistance against BB strains, high potential yields, and high grain quality were both developed and improved. The BB-pyramided breeding lines containing all five genes, *Xa4, xa5, Xa7, xa13* and *Xa21*, can serve as donors to introgress the resistance genes into other elite rice cultivars in order to accelerate the improvement of rice for disease resistance in Taiwan. These BB-pyramided lines are expected to have a high impact on domestic rice production stability, and also reduce the need for pesticides.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1422-0067/21/4/1281/s1. Figure S1: The polymorphic markers used for background selection of TNG82/IRBB66 backcross population. Table S1: The genome composition of BC2F2 derived from TNG82/IRBB66 by 117 polymorphic markers used for MAS.

**Author Contributions:** Conceptualization, Y.-C.H. and Y.-P.W.; methodology, Y.-P.W.; validation, Y.-P.W.; formal analysis, C.-H.C.; investigation, Y.-C.H., C.-H.C., R.Y., and Y.-P.W.; data curation, Y.-C.H. and R.Y.; writing—original draft preparation, Y.-C.H.; writing—review and editing, Y.-C.T. and Y.-P.W.; supervision, Y.-C.H. and Y.-P.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the Ministry of Science and Technology (MOST 108-2313-B-415-007) of Taiwan. We are grateful to National Plant Resources Center for providing the rice materials.

**Acknowledgments:** The authors are highly grateful to the technical support from Plant Protection Division, Chiayi Agricultural Experiment Station, Taiwan Agricultural Research Institute.

**Conflicts of Interest:** The authors declare that they have no conflict of interests.
