36. A new locus for resistance to brown planthopper in DV85, an indica rice (Oryza. Sativa L.)
  C.C. SU1, J. WAN1*, H.Q. ZHAI2, C.M.WANG1 and L H. SUN1

1) State Key Laboratory of Crop Genetics & Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing 210095, China
2) Chinese Academy of Agricultural Sciences, Beijing 100081, China
*) Corrsponding author, E-mail: wanjm@mail.njau.edu.cn; Tel.& Fax: 86-25-84396516

The brown planthopper (BPH), Nilaparvata lugens Stal, is one of the most serious insect pests of rice (Oryza sativa L.) in Asian rice growing area. BPH causes direct damage by sucking plant sap, and it also transmits several viral diseases such as rice grassy stunt (Rivera et al. 1966) and rugged stunt (Ling et al. 1978). Application of resistant varieties has been proved as one of the most economic and effective measure for BPH management.

In the study, we found that DV85, an indica rice, showed resistance to biotype 2 of BPH by bulked seedling test (Table 1). A recombinant inbred lines (RIL) population including 81 lines derived from a cross between susceptible rice Kinmaze and DV85 was phenotyped to map genetic factors conferring BPH resistance in DV85. The resistance scores of 81 RILs infested with biotype 2 showed a bimodal distribution (Fig. 1). If RILs with a resistance score lower than or equal to 5 were considered as resistance while above 5 were considered as susceptible, 42 RILs were resistant and 39 RILs were susceptible. The result fitted the expected ratio of 1:1 (chi2 = 0.111, c2 0.05 = 3.84, p = 0.05). Therefore there should be a major genetic factor gov-

erning the resistance segregation in this RIL population.

To tag the QTL for BPH resistance, we firstly tried to analyze cosegregation of RFLP markers with BPH resistance by using MAPMAKER/3.0 software (Lander et al. 1987), but we failed to map the resistance gene successfully even when the segregants with resistance score 4-6 were removed. So QTL analysis was carried out and one major QTL with a LOD score of 10.1 was detected between X202 and C1172 on chromosome 11 composite interval mapping (Table 2 and Fig 2). We designated this QTL as Qbph11. This QTL was near to C1172 and explained 68.4% of the phenotypic variance of BPH resistance in this population, thus it should be a QTL with major effects. As indicated by the additive effects estimated, this QTL was derived from resistant parent DV85 and reduced the damage caused by BPH feeding (Table 2). Since no BPH resistance gene has been located on chromosome 11, Qbph11 should be a new BPH resistance locus.

A pair of dominant resistance genes of DV85 with complementary expression to green rice leafhopper (GRH) and green leafhopper (GLH) have already been mapped on chromosome 3 and 11, which were designated as Grh4 and Grh2, respectively (Yazawa et al. 1998, Fukute et al. 1998,Yasui et al. 1999). The resistance gene on chromosome 11 was tightly linked to marker G1465. On the linkage map used in the present study, G1465 was only 9.5 cM distance to C1172 which was found to be near to Qbph11 (Fig.2). Chromosome region around G1465 and C1172 might be related to rice's resistance to such kinds of insects, or some sucking insects resistance genes might cluster in this chromosome region of DV85. However, we could not detect resistance QTL on chromosome 3, which might not confer resistance to BPH.

Acknowledgements

The authors thanks Professor A.Yoshimura in Plant breeding Laboratory, Faculty of Agriculture, Kyushu University, for his kindly providing us the RIL population and genotype data.

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