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(1) International Rice Research Insitute, P.O. Box 933, Manila, Philippines
(2) Tropical Agriculture Research Center, Tsukuba, Ibaraki, 305 Japan
The Xa-3 gene for resistance to Japanese races of rice bacterial blight (caused
by Xanthomonas campestris pv. oryzae) was first identified in Wase Aikoku 3 by
Ezuka et al. (1975) and designated as Xa-w. However, inheritance of resistance
to tropical races in Wase Aikoku could not be studied as it was difficult to
grow Wase Aikoku in tropics.
We have now completed genetic analysis of resistance in Wase Aikoku 3, Chugoku 45, and Java 14, (all with Xa-3 gene), using Japanese and Philippine races. Inoculation for genetic analysis was done by the clipping method at booting to flowering stage of plants. Inoculum was suspended at a concentration of approximately 108-109 cells per ml. Scoring and evaluation were done during the period of two weeks up to one month after inoculation. The studies were conducted both at International Rice Research Institute (IRRI) and at Tropical Agriculture Research Center (TARC), Japan, using isolates originating from respective countries.
Chugoku 45 is a progeny of Wase Aikoku 3 but had not been analyzed genetically before. Java 14 was analyzed by Ezuka et al. (1975) and Ogawa et al. (1978) and found to have Xa-3. In the present study, when the F\2\ populations from crosses, among Wase Aikoku 3, Chugoku a 45 and Java 14 were inoculated with Japanese races at TARC, no susceptible plants were observed (Table 1). These results show that Chugoku 45, Wase Aikoku 3 and Java 14 have Xa-3 for resistance.
The studies at IRRI showed that F\1\ plants of Toyonishiki x Chugoku 45 and
Toyonishiki x Java 14 were resistant to Philippine races 1,2,3 and 4. The F\2\
populations of these two crosses showed a segregation ratio of 3: 1 of RRRR
(resistant to races 1 to 4): SSSS (susceptible to races 1 to 4). The F\2\
populations of Wase Aikoku 3xChugoku 45 and Chugoku 45xJava 14 showed no
segregation for susceptibility (Table 1). These results also show that Wase
Alkoku 3. Chugoku 45, and Java 14 each have one and the same for the resistance
to four Philippine races.
Ezuka, A., O. Horino, K. Toriyama, H. Shinoda and T. Morinaka, 1975.
Inheritance of resistance of rice variety Wase Aikoku 3 to Xanthomonas oryzae.
Bull. Tokai-Kinki Nat'l Agric. Exp. Stn. 28: 124-130.
Ogawa, T., T. Morinaka, K. Fujii and T. Kimura, 1978. Inheritance of rice
varieties of Kogyoku and Java 14 to bacterial group V of Xanthomonas oryzae.
Ann. Phytopathol. Soc. Japan 44:137-141.
Table 1. Data on the reactiona to bacterial blight of F\1\ and F\2\ progenies
at booting to flowering stages=============================================================================
Crosses F\1\ reaction F\2\ reaction X2 P
to 4 races to 4 races 3:1
=============================================================================
(at IRRI)
RRRR(No.) SSSS(No.)
========= =========
1. Toyonishiki/Chugoku 45 RRRR 193 65 0.005 >0.99
2. Toyonishiki/Java 14 RRRR 187 78 2.779 0.5-0.7
3. Wase Aikoku 3/Chugoku 45 RRRR 226 0
4. Chugoku 45/Java 14 RRRR 547 0
=============================================================================
(at TARC)
R(No.) S(No.)
===================
5. Wase Aikoku 3/Kinmaze R 174 55 0.118 0.8-0.9
6. Chugoku 45/Kinmaze R 172 62 0.279 0.5-0.7
7. Toyonishiki/Chugoku 45 R 232 75 0.053 0.8-0.9
8. Kinmaze/Java 14 R 98 33 0.002 >0.99
9. Toyonishiki/Java 14 R 275 75 2.381 0.1-0.2
10.Wase Aikoku 3/Java 14 R 289 0
11.Chugoku 45/Wase Aikoku 3 R 266 0
12.Chugoku 45/Java 14 R 160 0
=============================================================================
aR=resistant, S=susceptible
For reaction of crosses 1-4: the first letter stands for reaction to race 1,
second for race 2, third for race 3, and fourth for race 4 of Philippines.
For crosses 5-10: Japanese isolate T7133 (race IIIA) was used for
inoculation.
References
