4. Establishment of differential varieties for pathogenicity test of rice blast fungus

Shigehisa KIYOSAWA

National Institute of Agrobiological Resources, Yatabe, Tsukuba, Ibaraki, 305 Japan

Varieties with different single resistance genes are ideal differential varieties for pathogenicity test of the pathogen (Flor 1945). In Japan, the first differential varieties for rice blast were chosen by Goto and co-workers (1961, 1964). Yamasaki and Kiyosawa (1966) initiated gene analysis using seven fungus strains selected in the light of Goto's work and detected three resistance genes, Pi-a, Pi-i and Pi-k. Since then, 13 genes have been identified (Kiyosawa 1972). Since 1960's, the author has tried to develop lines with a single gene from varieties having more than one gene. For example, resistance gene Pi-ta was isolated from the hybrid between Pi No. 1 having Pi-a and Pi-ta and Norin 8 which has no resistance gene (Kiyosawa 1966). Line K 1 with Pi-ta was thus obtained (Kiyosawa 1967). Also, line K 60 with Pi-kp was obtained from K 2 x Shin 2; K 2 having Pi-a and Pi-kp was derived from Pusur x Norin 22. Pi-kp was first found in Pusur, a variety from Pakistan (Kiyosawa 1969). K 59 with Pi-t was obtained from BL 10 (Pi-b Pi-t) x Kanto 51 (Pi-k) (Kiyosawa 1972).

The strains with different single resistance genes thus obtained, as listed in Table 1, are useful as differential varieties to classify fungus isolates into groups differing in pathogenicity. In addition, another set of differential varieties was established by Yamada et al. (1976, included in Table 1). By the use of these differential varieties, it has become possible to estimate the structure of populations of the blast fungus in terms of frequency of virulence and avirulence genes. However, it is possible that some of these differential varieties have more than one gene if fungus strains of alien origin are tested.

Table 1. Differential varieties and their resistance genes

=============================================================================
  Differential varieties of

                               Gene    Code number  Literature
Kiyosawa     Yamada et al.
=============================================================================
Shin 2       Shin 2            Pi-ks          1     Kiyosawa        1969
Aichi Asahi  Aichi Asahi       Pi-a           2     Kiyosawa et al. 1967
Fujisaka 5   Ishikari-shiroke  Pi-i           4     Yamasaki and Kiyosawa 1966
Kusabue      Kanto 51          Pi-k          10     Yamasaki and Kiyosawa 1966
                                                    Kiyosawa     1968
Tsuyuake     Tsuyuake          Pi-km         20     Kiyosawa      1978
Fukunishiki  Fukunishiki       Pi-z          40     Kiyosawa      1970
K 1          Yashiro-mochi     Pi-ta        100     Kiyosawa      1967,1969
Pi No. 4     Pi No. 4          Pi-ta2       200     Kiyosawa        1969
Toride 1     Toride 1          Pi-zt        400     Yokoo and Kiyosawa 1970
K 60                           Pi-kp          .1    Kiyosawa unpublished
BL 1                           Pi-b           .2    Yokoo et a]. 1978
K 59                           Pi-t           .4    Kiyosawa        1972
=============================================================================
     Note: Race number is determined by adding the code number of varieties
which show virulent reaction.  For example, the race number of isolate which
shows virulent reactions to Shin 2 and Kusabue is 1 + 10 = 11.

References

Flor, H. H., 1945. Identification of races of flax rust by lines with single rust-conditioning genes. U.S. Dept. Agr. Tech. Bull. 1087.

Goto, K. (with 10 co-workers), 1961. Joint Work on the Race of Blast Fungus, Piricularia oryzae. Special Report on Forecasting of Occurrence of Disease and Insect Pest, No. 5 pp. 89(in Japanese).

Goto, K. (with 16 co-workers), 1964. Ditto, 2. Special Report on Forecasting of Occurrence of Disease and Insect Pest, No. 18 pp.132 (in Japanese).

Kiyosawa, S., 1966. Studies on inheritance of resistance of rice varieties to blast, 3. Inheritance of resistance of a rice variety Pi No. I to the blast fungus. Jpn. J. Breed. 16: 243-250.

Kiyosawa, S., 1967. Genetic studies on host-pathogen relationship in the rice blast disease. Proc. Symp. Rice Diseases and their Control by Growing Resistant Varieties and Other Measures. Tokyo, p. 137-153.

Kiyosawa, S. 1968. Inheritance of blast resistance in some Chinese rice varieties and their derivatives. Jpn. J. Breed. 18(4): 193-205.

Kiyosawa, S. 1969. Inheritance of resistance of rice varieties to a Philippine fungus strain of Pyricularia oryzae. Jpn. J. Breed. 19(2): 61-73.

Kiyosawa, S. 1970. Comparison among various methods for testing blast resistance of rice varieties. Ann. Phytopath. Soc. Japan 36(5): 325-333 (in Jap.)

Kiyosawa, S. 1972. The inheritance of blast resistance transferred from some indica varieties of rice. Bull. Natl. Inst. Agr. Sci. D23: 69-95.

Kiyosawa, S. 1978. Identification of blast-resistance genes in some rice varieties. Jpn. J. Breed. 28(4): 287-296.

Yamada, M., S. Kiyosawa, T. Yamaguchi, T. Hirano, T. Kobayashi, K.Kushibuchi, and S. Watanabe, 1976. Proposal of a new method for differentiating races of Pyricularia oryzae Cavara in Japan. Ann. Phytopathol. Soc. Japan 42: 216-219.

Yamasaki, Y. and S. Kiyosawa, 1966. Studies on inheritance of resistance of rice varieties to blast, 1. Inheritance of resistance of Japanese varieties to several strains of the fungus. Bull. Natl. Inst. Agr. Sci. D14: 39-69 (in Jap.).

Yokoo, M. and S. Kiyosawa, 1970. Inheritance of blast resistance of the rice variety, Toride 1, selected from the cross Norin 8 x TKM 1. Jpn. J. Breed. 20: 129-132.

Yokoo, M., F. Kikuchi, H. Fujimaki and K. Nagai, 1978. Breeding of blast resistant line (BL 1 to BL 7) from indica-japonica crosses of rice. Jpn. J. Breed. 28: 359-365. (in Jap.)