1) Tohoku Natl. Agric. Exp. Station, Omagari, Akita, 014-01, and
2) Agric. Fores. Fish. Res. Council Secretary, MAFF, 1-2-1 Kasumigaseki, Chiyoda-ku, Tokyo, 100 Japan
The brown planthopper, Nilaparvata lugens Stal. (abbr. BPH), is one of
most serious pests of rice throughout Asia. The inheritance of BPH resistance
has been investigated by many workers since Athwal et al. (1971). To date,
four genes, Bph-1, bph-2, Bph-3 and bph-4, have been found (Athwal et al.
1971; Lakshminarayana and Khush 1977). We also have been engaged in genic
analysis for the resistance.
First, to determine whether or not two or more resistance genes can be combined in a variety, allelism tests were made. The results indicated that, as reported previously (Sidhu and Khush 1978; Ikeda and Kaneda 1981), Bph-1 and bph-2 are linked closely, and so are Bph-3 and bph-4. The two linkage groups, however, are independent.
Second, to identify the chromosomes on which the BPH resistance genes are located, each of the trisomic lines obtained from Kyushu University were crossed with Kanto PL 1 or Kanto PL 4 (having Bph-1), Rathu Heenati (having Bph-3) and Babawee (Having bph-4). In the cross with trisomic line E, which has chromosome 11 in triplicate, the F\2\ ratio for Bph-1 significantly differed from 3 : 1 and agreed with a trisomic ratio of 2 : 1. Bph-1 was thus located on chromosome 11 (linkage group 11). Linkage tests showed that bph-2 was linked with d-2 belonging to linkage group 11, the recombination value being 39.4%. Both Bph-1 and bph-2 segregated independently of 1g, P11 and d-11 which belong to linkage group 11 but are distant from d-2.
Similarly, Bph-3 and bph-4 were found to be located on chromosome 7 (to which no linkage group is assigned yet); trisomic ratios of 2 : 1 for Bph-3 and 1 : 17 for bph-4 were found in crosses with trisomic line C having chromosome 7 in excess (Table 1).
Furthermore, three cultivars with unknown resistance genes, Andaragahawewa, PTB 34, and PTB 21, were crossed with resistant and susceptible testers to identify their resistance genes. The results showed that Andaragahawewa and PTB 34 had Bph-1 and bph-2, respectively. PTB 21 had been known to have a dominant and a recessive gene, one of them being either Bph-1 or bph-2 (Lakshmirarayana and Khush 1977). Our data indicated that the second gene of PTB 21 was either Bph-3 or bph-4. Then, 12 F\3\ lines from Kochihibiki/PTB 21//Asominorl were tested with BPH biotypes I, II and III. The result showed that one of the two genes was bph-2. Accordingly, it was concluded that PTB 21 had bph-2 and Bph-3. Although this variety had two resistance genes, but it had no new resistance gene.
Table 1. F2 ratios for resistance to BPH in the crosses of trisomic
lines with Kanto PL 4 (BPh-1), Rathu Heenati (Bph-3), and Babawee (bph-4)
=============================================================================
Resistance Cross No. of F2 plants x2 (3:1
gene R S Total or 1:3)
=============================================================================
Bph-1 Trisomic E/Kanto PL4 337 182 519 28.1**a
Control (disomic) 981 350 1331 1.2
Bph-3 Trisomic C/Rathu Heenati 78 42 120 7.6**a
Control (disomic) 164 64 225 1.4
bph-4 Trisomic C/Babawee 8 306 314 84.4**b
Control (disomic) 203 634 837 0.3
=============================================================================
Significant at 1% level. a - fitting 2 : 1, b - fitting 1: 17. Crosses of
other trisomic lines, A, C, G, and H with Bph-1, H with Bph-3, and A, E, F,
and L with bph-4, all gave a good fitness to 3 : 1 or 1 : 3 ratio.
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.
Ikeda, R. and C. Kaneda, 1981. Genetic analysis of resistance to brown planthopper, Nilaparvata lugens Stal., in rice. Jpn. J. Breed. 31: 279-285.
Lakshminarayana, A. and G. S. Khush, 1977. New genes for resistance to the brown plant-hopper in rice. Crop Sci. 17: 96-100.
Sidhu, G. S. and G. S. Khush, 1978. Genetic analysis of brown planthopper resistance in twenty varieties of rice, Oryza sativa L. Theo. Appl. Genet. 53: 199-203.