21. The specific reaction of Taichung Native 1 to Philippine races of bacterial blight and inheritance of resistance to race 5 (PXO112)

S. TAURA1, T. OGAWA1, R. E. TABIEN1, G. S. KHUSH1, A. YOSHIMURA2 and T. OMURA2

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

2) Faculty of Agriculture, Kyushu University, Higashi-ku, Fukuoka, 812 Japan

During the inoculation test using Philippine races of bacterial blight, variety Taichung Native 1 (TN1) showed a specific reaction. It is resistant only to race 5 (PXO112) but is very susceptible to other five races (races 1, 2, 3, 4, and 6). Its reaction was compared with other differential varieties by inoculating with 6 Philippine races (Table 1). The data showed that there was no other differential similar to the reaction pattern of TN 1. Therefore, it appeared that TN 1 has a new gene for resistance to race 5. We carried out analysis to determine the inheritance of resistance to race 5 of TN1.

We crossed TN1 with susceptible varieties, Toyonishiki and Milyang 23, and with a Japanese differential variety Te-tep. The F1 plants and the F2 populations were inoculated with four Philippine races (races 1, 2, 4 and 5). In addition, the backcross progeny (IR24/TN1//IR24) was also analyzed.

All F1 plants showed resistance only to race 5. Therefore, the resistance gene of TNI appeared to be dominant.

The F2 populations of Toyonishiki/TN1, Milyang 23/TN1 and TN1/Te-tep were susceptible to races 1, 2 and 4 but clearly segregated in a ratio of 3 resistant: 1 susceptible for race 5 (Table 2). In the backcross progeny of IR24/TN1//IR24, there were 98 resistant: 97 susceptible plants (a 1 : 1 ratio). These results confirm that the resistance of TN1 to race 5 is governed by a single dominant gene. This kind of reaction pattern to Philippine races has not been found before. As shown in Table 1, Japanese differentials having any of the genes Xa-1, Xa-2, Xa-12 (Xa-kg) and Xa-3 also did not show this kind of reaction pattern.

Following the rules of gene symbolization in rice we have designated the dominant gene for resistance to race 5 in TN1 as Xa-14. In common with Te-tep (Xa-1/Xa-2), TN1 shows resistance to Japanese races IA, IB and II (Ogawa and Yamamoto 1987). Therefore, we plan to study the relationships between Xa-1/ Xa-2 and the new gene. It should be noted that Te-tep does not show resistance to race 5 in the Philippines.

Table 1. The reaction of differential rice varieties to 
Philippine races of bacterial blight at booting stage
________________________________________________________________
                Race 1  Race 2  Race 3  Race 4  Race 5  Race 6
Variety        _______ _______ _______ _______ _______ _______
               LL  RE  LL  RE  LL  RE  LL  RE  LL  RE  LL  RE
________________________________________________________________
IR24(+)       25.7  S 35.6  S 32.5  S 31.6  S 22.7  S 36.0  S
Milyang 23(+) 15.3  S 26.5  S 28.5  S 31.3  S 24.9  S 43.5  S
Toyonishiki(+) 8.3 MS 17.0  S 16.2  S 11.6  S 12.9  S 21.2  S
TN1           19.6  S 35.2  S 37.4  S 31.5  S  4.9  R 30.7  S
Tetep(Xa-1,
Xa-2)         14.5  S 30.7  S 29.1  S 26.5  S 17.0  S 33.1  S
Chugoku 45
(Xa-3)         0.4  R  1.9  R  2.2  R  1.3  R  3.5  R 11.5  S
Java 14 (Xa-1, 
Xa-3, Xa-12)   0.6  R  2.3  R  1.4  R  2.9  R  6.9  R 24.4  S
IR8 (Xa-11)   17.0  S 25.6  S 28.7  S 14.9  S 13.6  S 19.5  S
IR20 (Xa-1, 
Xa-4)          6.9  R 22.5  S 24.5  S  9.7 MS  3.9  R 18.3  S
IR1545-339 
(xa-5)         1.2  R  2.6  R  1.1  R 17.9  S  4.4  R 30.0  S
DV85(xa-5,Xa-7)0.4  R  0.4  R  0.5  R  6.0 MR  2.0  R  6.5 MR
Cas209(Xa-10) 24.2  S  3.5  R 45.3  S 40.0  S  1.7  R 50.4  S
BJ1(xa-5,Xa-13)0.6  R  3.8  R  2.8  R  4.7  R  0.6  R  3.7  R
PI231129(xa-8) 3.5  R  8.0  R  6.5  R 12.2 MS  5.5  R  4.5  R
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LL: Average lesion length in cm from 15 inoculated leaves (3 leaves from 5 plants) at 14 days after inoculation.

RE: R = resistant; MR = moderately resistant; MS = moderately susceptible; and S = susceptible.

Table 2. The reaction of F1 and F2 Populations from the crosses of TN1 with four varieties to four races (Races 1, 2, 4, 5) of bacterial blight

________________________________________________________________
Crosses                            Reaction of 
                                  F2 Populations   X2      P
                  Reaction of F1 _______________
                   progenies       SSSR   SSSS    3:1
________________________________________________________________
Toyonishiki/TN1     SSSR            185    84    5.56  0.01-0.02
Milyang 23/TN1      SSSR            200    70    0.12  0.7 -0.8
TN1/Tetep           SSSR            208    57    1.72  0.1 -0.2
________________________________________________________________
R=resistant; S=susceptible

References

Ogawa, T. and T. Yamamoto, 1987. Selection of recurrent parents to develop near-isogenic lines resistant to bacterial leaf blight of rice. JARQ, 21: 65-69.