Substitution mapping and characterization of brown planthopper resistance genes from traditional rice cultivar ‘Rathu Heenati’ (<i>Oryza sativa</i> L.)

The brown planthopper (BPH; <i>Nilaparvata lugens</i> Stål) is a devastating pest that causes severe rice yield losses in Asia. Introducing multiple BPH resistance genes into rice cultivars is an effective and sustainable way to mitigate yield losses. A traditional rice cultivar, 'Rathu Heenati', has durable BPH resistance due to multiple resistance genes (including <i>BPH3</i> and <i>BPH17</i>) and quantitative trait loci (QTLs). However, these genes have not been used in Japanese rice breeding owing to limited genetic information. To identify markers tightly linked to <i>BPH3</i> and <i>BPH17</i> introgressed into the 'Sagabiyori' (susceptible) genetic background, we performed substitution mapping. <i>BPH3</i> was delimited between RM3132 and RM589 on chromosome 6, and <i>BPH17</i> between RM16493 and RM16531 on chromosome 4. We also performed QTL analysis to identify additional BPH resistance genes from 'Rathu Heenati' and detected a QTL, denoted as <i>qBPH3.1</i>, on chromosome 3. The effect of pyramiding <i>BPH3</i> and <i>BPH17</i> was significantly greater against virulent BPH populations than that of either gene alone. The combination of <i>BPH3</i>, <i>BPH17</i> and <i>qBPH3.1</i> from 'Rathu Heenati' might be facilitated to improve commercial Japanese cultivars with more robust BPH resistance.