Identification and mapping of two brown planthopper resistance genes in rice

The brown planthopper (BPH) is one of the most serious insect pests of rice . In this study, we conducted a molecular marker-based genetic analysis of the BPH resistance of 'B5', a highly resistant line that derived its resist ant genes from the wild rice Oryza Officinalis. Insect resistance was evalu ated using 250 F-3 families from a cross between 'B5' and 'Minghui 63', bas ed on which the resistance of each F, plant was inferred. Two bulks were ma de by mixing, respectively, DNA samples from highly resistant plants and hi ghly susceptible plants selected from the F, population. The bulks were sur veyed for restriction fragment length polymorphism using probes representin g all 12 chromosomes at regular intervals. The survey revealed two genomic regions on chromosome 3 and chromosome 4 respectively that contained genes for BPH resistance. The existence of the two loci were further assessed by QTL (quantitative trait locus) analysis, which resolved these two loci to a 14.3-cM interval on chromosome 3 and a 0.4-cM interval on chromosome 4. Co mparison of the chromosomal locations and reactions to BPH biotypes indicat ed that these two genes are different from at least nine of the ten previou sly identified BPH resistance genes. Both of the genes had large effects on BPH resistance and the two loci acted essentially independent of each othe r in determining the resistance. These two genes may be a useful BPH resist ance resource for rice breeding programs.