The virulence of laboratory strains of the brown planthopper (BPH), Nilaparvata lugens (Stål), and the whitebacked planthopper (WBPH), Sogatella furcifera (Horváth), collected in Japan between 1966 and 2005, was evaluated using rice differential varieties carrying different planthopper resistance genes. The BPH strain collected in 1966 was avirulent to all the rice varieties tested. In contrast, the 1989, 1999 and 2005 strains were virulent to Mudgo, which carries Bph1. The 1999 and 2005 strains were virulent to ASD7 (bph2). Thus, the virulence status of the laboratory BPH strains was the same as in previous reports. The 1989The , 1999The , and 2005 WBPH strains were virulent to N22 (Wbph1), Mudgo, ASD7, Babawee (bph4) and Chin Saba (bph8); the 1999 and 2005 WBPH strains were also virulent to ARC10239 (Wbph2). Although the virulence status of WBPH in Japan has not previously been studied, the present results suggest that the effectiveness of the Wbph1 resistance gene broke down before 1989, while that of Wbph2 broke down between 1989 and 1999. The present study showed that long-term mass rearing in the laboratory has not affected virulence status. Thus, these strains will be useful to analyze resistance genes against BPH and WBPH.

The brown planthopper (BPH), Nilaparvata lugens (Stål), is one of the most serious and destructive pests of rice, and can be found throughout the rice-growing areas of Asia. To date, more than 24 major BPH-resistance genes have been reported in several Oryza sativa ssp. indica cultivars and wild relatives. Here, we report the genetic basis of the high level of BPH resistance derived from an Indian rice cultivar, ADR52, which was previously identified as resistant to the whitebacked planthopper (Sogatella furcifera [Horváth]). An F2 population derived from a cross between ADR52 and a susceptible cultivar, Taichung 65 (T65), was used for quantitative trait locus (QTL) analysis. Antibiosis testing showed that multiple loci controlled the high level of BPH resistance in this F2 population. Further linkage analysis using backcross populations resulted in the identification of BPH-resistance (antibiosis) gene loci from ADR52. BPH25 co-segregated with marker S00310 on the distal end of the short arm of chromosome 6, and BPH26 co-segregated with marker RM5479 on the long arm of chromosome 12. To characterize the virulence of the most recently migrated BPH strain in Japan, preliminary near-isogenic lines (pre-NILs) and a preliminary pyramided line (pre-PYL) carrying BPH25 and BPH26 were evaluated. Although both pre-NILs were susceptible to the virulent BPH strain, the pre-PYL exhibited a high level of resistance. The pyramiding of resistance genes is therefore likely to be effective for increasing the durability of resistance against the new virulent BPH strain in Japan.

No abstract

No abstract

No abstract