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.
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.
Fukuta Y., K. Tamura, M. Hirae, S. Oya, 1998. Genetic analysis of resistance
to green rice leafhopper (Nephotettix cincticeps UHLER) in rice
parental line, norin-PL6, using RFLP markers. Breed. Sci., 48:
Ling, K. C. E.R. Tiongco and V. M. Aguiero, 1978. Rice ragged stunt, a
new virus disease.Plant Dis Rep. 62: 701-705.
Lander E.S., P. Green. J. Abrahamson, M. J. Barlow, M.J. Daly, S.E. Lincoln
and L. Newburg, 1987. MAPMALER: an interactive computer for constructing
primary genetics linkage maps of experimental and natural populations.
Genomics 1: 174-181.
Rivera C. T., S. H. Ou and T. T. Lida, 1966. Grassy stunt disease of rice
and its transmission by Nilaparvata lugens (Stal). Plant Dis. Rep.
Yasui H. and A.Yoshimura, 1999. QTL mapping of antibiosis to green leafhopper,
Nephotettix virescens Distant and green leafhopper, Nephotettix
cincticeps Uhler in rice, Oryza sativa L. Rice Genet. Newsl.
Yazawa,S., H.Yasui, A.Yoshimura and N.Iwata, 1998. RFLP mapping of genes
for resistance to green rice leafhopper (Nephotettix cincticeps
Uhler) in rice cultivar DV85 using near isogenic lines. Sci. Bull. Fac.
Agr. Kyushu Univ. 52: 169-175. (Japanese with English summary).