LAUSR

The brown planthopper (Nilaparvata lugens Stål; BPH) is the most destructive rice pests worldwide. Identification and application of major resistance genes and cultivation of resistant varieties are the most efficient methods to control this insect. In this study, the rice variety, ARC5984, was detected to be highly resistant to BPH due to the presence of a major resistance gene, which has primarily been mapped in a 6-cM region on the long arm of chromosome 4. Fine mapping of the resistance gene was performed using the recombinants derived from BC1F2 individuals; the target gene was described to be a 46-kb region in the Nipponbare genome. Based on the information on the genomic sequences of the varieties Nipponbare, ZS97 and MH63, six, seven and 11 candidate genes were identified in the finally located region, respectively. The relative expression of the candidate genes Os04g35190 and Os04g35210 was significantly different between the resistant and susceptible plants after BPH infestation. The sequencing results indicated the coding domain sequence (CDS) of Os04g35210 from ARC5984 to be identical to that of Bph6. But the CDS of Os04g35190 was different between in ARC5984 and 9311. Moreover, the preliminary-near-isogenic lines (pre-NILs; the lines carrying resistance genes) with genetic background of the 9311 showed significant antixenosis to BPH, and thus, restricted its growth and development when compared with that in the susceptible line of 9311. Finally, a marker-assisted selection (MAS) technique was developed for the markers, RM5635 and BF9; its efficiency has been confirmed by applying it in screening of backcrossed individuals. The development in the fine mapping of the major gene will facilitate efforts of cloning this important resistance gene and to apply it in breeding of BPH-resistance rice varieties.