31. The distribution of resistance genes to the brown planthopper in rice germplasm

Ryoichi IKEDA and Duncan A. VAUGHAN

International Rice Research Institute, P.O. Box 933, Manila, Philippines

The brown planthopper (BPH) is one of the most serious rice pests in tropical and temperate Asia. Since Athwal et al. (1971) identified Bph-1 and bph-2 genes in Mudgo and ASD 7, respectively, nine resistance genes have been reported to date. Four biotypes of BPH are known. Biotypes 1 is widely distributed in East and Southeast Asia; biotype 2 originated in Philippines after widescale cultivation of varieties with Bph-1 gene and biotype 3 was produced in laboratories in both Japan and the Philippines. Biotype 4 is found only in South Asia. The varieties have been classified into three groups in the Philippines and Japan as follows: (1) Bph-1 group; resistant to biotypes 1 and 3 but susceptible to biotype 2, (2) bph-2 group; resistant to biotypes 1 and 2 but susceptible to biotype 3, and (3) the group with Bph-3, bph-4, bph-8 or Bph-9; resistant to all three biotypes. The other three genes, bph-5, Bph-6 and bph-7 convey resistance to biotype 4 only.

1. Cultivated varieties

In Japan, Kaneda et al. (1981) reported the results of screening about 3,300 cultivars and breeding lines from different regions of the world. Most of the resistant traditional cultivars came from Kerala, Tamil Nadu and Andhra Pradesh states of southern India and Sri Lanka. Based on the reaction patterns of these varieties to different biotypes the proportion of resistance genes found in Sri Lankan traditional varieties was different from those in India. About 60 per cent of the Sri Lankan cultivars were found to possess the bph-2, in contrast only 10 per cent of the Indian cultivars tested had this gene. Heinrichs et al. (1985) also listed the resistant varieties with the reaction to three biotypes at IRRI, the Philippines, and the results are similar to those of Kaneda et al. (1981). Out of 272 resistant varieties, 193 (717o) were from Sri Lanka with most varieties show- ing resistance to 2 biotypes and 62 (237o) were from India with most varieties showing resistance to all 3 biotypes (Table 1). Khush (1977) also reported that most BPH resistant varieties came from Sri Lanka and neighboring states of India.

South India and Sri Lanka may be considered a secondary center for rice diversity with a wealth of wild species and rice cultivation dating back to more than several thousand years. Irrigation tanks which may have permitted double cropping of rice were built by the fifth century AD in Sri Lanka (Watabe 1990). Under intensive cultivation BPH biotypes and resistant cultivars evolved. The Palk Strait between Sri Lanka and India, although narrow, acts, as a barrier to biological movement. There are many differences between the flora of Sri Lanka and Tamil Nadu. Currently Sri Lankan breeders are using sources of resistance to BPH from India, such as Ptb33, since Sri Lankan traditional varieties are now 

Table 1.  Distribution of BPH resistant varieties in India and Sri Lanka
===============================================================================
                                            Reactions to three biotypes2)  
Origin of Country  Location of test1)   =======================================
                                              RRR    RSR    RRS    Total
===============================================================================
India                   NARC                   20     12      5       37
                                             (54%)  (32%)   (14%)
                        IRRI                   32     25      5       62
                                             (52%)  (40%)   (8%)

Sri Lanka               NARC                   15     24     49       88
                                             (17%)  (27%)   (56%)
                        IRRI                   52     57     84      193
                                             (27%)  (29.5%) (43.5%)
===============================================================================
1) NARC, IRRI; cited from Kaneda et al. (1981), Heinrichs et al. (1985),
respectively,
2) reactions to biotypes 1, 2, and 3.
susceptible to the BPH diversity of Sri Lanka (D. Senadhira, pers. comm.).

2. Wild relatives of rice

Resistance to each BPH biotype is encountered about 30 times more frequently in populations of wild rices than in cultivated varieties. However, the resistance to all three biotypes in wild relatives was found to be even higher; more than 50 times the occurrence in traditional varieties (IRRI, 1991) (Table 2). Broad resistance to BPH biotypes is thus more common in wild than in the cultivated rices.

Heinrichs et al. (1985) listed 12 species and natural species hybrids resistant to BPH. Five species, O. nivara, O. ridleyi, O. officinalis, O. minuta, O. australiensis, and natural hybrids are distributed in Asia or tropical Australia. This may be considered sympatric resistance since the distribution of these species matches the 

       
Table 2.  Screening of varieties and wild relatives for resistance to BPH at
IRRI 1991 (from database for GEU program)
===============================================================================
                               Variety                   Wild relatives
                     ===========================   ============================
                     Total    Resistant     (%)    Total    Resistant      (%)
===============================================================================
Biotype1)  
      1              44,335       682     (1.5)    723           302     (41.8)
      2              10,053       187     (1.9)    724           242     (33.4)
      3              13,021       236     (1.8)    730           272     (37.3)

Reaction patterns2)   7,022                        579
     RRR                           48     (0.7)                  219     (37.8)
     RSR (Bph-1)                  121     (1.7)                   14      (2.4)
     RRS (bph-2)                   83     (1.1)                    3      (0.5)
===============================================================================
1)reactions to each biotype
2)reactions to 3 biotypes (biotypes 1, 2 and 3)
distribution of the BPH. However, the other species of Africa and tropical America, O. brachyantha, O. barthii, O. punctata, O. glumaepatula, O. latifolia, O. alta, and African strains of O. eichingeri exhibit allopatric resistance (Table 3). In particular, the BPH resistance in populations of O. latifolia showed differential reaction patterns as five accessions were resistant to all three biotypes, four exhibited the reaction pattern associated with Bph-1, four showed the reaction pattern associated with bph-2. This reveals that BPH is compatible with O. latifolia and this resistance is not a species characteristic (Table 3). 

       
Table 3. Wild rice species resistant to BPH (cited from Heinrichs et al.
1985)
===============================================================================
Species complex      Genome                       Resistant to BPH
      Taxa            group           =========================================
                                        RRR             RSR             RRS
===============================================================================
O. branchyantha        FF                2
O. sativa complex
O. nivara              AA                9               1
Natural hybrids        AA                3                               1
O. barthii             AA                2               1
O. glumaepatula        AA                1
O. ridleyi complex
O. ridleyi             tetraploid        2
O. officinalis complex
O. officinalis         CC               37               2
O. eichingeri          CC                5                               2
O. minata              BBCC             28
O. punctata            BB,BBCC           7                               5
O. latifolia           CCDD              5               4               4
O. alta                CCDD              1
O. australiensis       EE                4
===============================================================================
When sources of resistance to a stress can be found both where the stress is present and where it is absent, it may be worthwhile analyzing gene differences from both sources. Genes arising from coevolution in a gene for gene manner can be overcome by a pathogen. A stress tolerance which arises independently of the stress may be more difficult to breakdown (Harris 1975).

References

Athwal, D. S., M. D. Pathak, E. H. Bacalangco and C. D. Pura, 1971. Genetics of resistance to brown planthoppers and green leafhoppers in Oryza sativa L. Crop Sci., 11: 747-750.

Harris, M. K., 1975. Allopatric resistance: searching for sources of insect resistance for use in agriculture. Environ. Entom. 4: 661-669.

Heinrichs, E.A., F.G. Medrano and H.R. Rapusas, 1985. Genetic evaluation for insect resistance in rice. pp. 356, IRRI, Los Banos, Lagna, Philippines IRRI 1991. Database for GEU program at IRRI.

Kaneda, C., K. Ito and R. Ikeda, 1981. Screening of rice cultivars for resistance to the brown planthopper, Nilaparvata lugens Stal., by three biotypes. Jpn. J. Breed. 31(2): 141-151.

Khush, G. S., 1977. Disease and insect resistance in rice. Advances in Agronomy 29: 265-341. Watabe, T., 1990. The roots of the rice we eat. Tracing the history of rice cultivation. pp. 219, PHP Res. Inst. Tokyo, Japan (in Japanese).