1) International Rice Research Institute, PO Box 933, Manila Philippines
2) Tropical Agriculture Research Center, 1-3 Ohwashi, Tsukuba, Ibaraki-ken, 305 Japan
Different sets of differential cultivars have been utilized for characterizing
races of bacterial blight in different countries. Thus there are Japanese
differentials and Philippine differentials. A universal system of race
identification is not possible without using an international set of
differentials. Near isogenic lines with different genes for resistance are
ideal for establishing an international differential set. Such an international
differential set can be utilized not only for identifying races but also for
identifying new genes for resistance. Moreover, isogenic lines can serve as
donors for resistance in breeding program and are excellent materials for
studying the mechanism of resistance.
Table 1. Near-isogenic lines for resistance to bacterial blight of rice
developed to date.
=============================================================================== Designation Cross1 Generation R gene =============================================================================== Ir BB 1 Ir24*5/Kogyoku BC\4\F\4\ Xa-1 (Xa-12) IR BB 101 Toyo*5/Kogyoku " " " IR BB 201 M 23*5/Kogyoku " " " IR BB 3 IR24*5/Chugoku 45 BC\4\F\6\ Xa-3 IR BB 103 Toyo*5/Chugoku 45 " IR BB 203 M 23*5/Chugoku 45 BC\4\F\7\ " IR BB 3J IR24*5/Java 14 BC\4\F\6\ " IR BB 103J Toyo*5/Java 14 " " IR BB 203J M 23*5/Java 14 " " IR BB 3Z IR24*5/Zenith " " IR BB 103Z Toyo*5/Zenith " " IR BB 203Z M 23*5/Zenith " " IR BB 3S IR24*5/Sateng " " IR BB 103S Toyo*5/Sateng " " IR BB 203S M 23*5/Sateng " " IR BB 4 IR24*5/IR20 " Xa-4 IR BB 104 Toyo*5/IR20 " " IR BB 204 M 23*5/IR20 " " IR BB 5 IR24*5/IR1545-339 BC\4\F\5\ xa-5 IR BB 105 Toyo*5/IR1545-339 BC\4\F\4\ " IR BB 205 M 23*5/IR1545-339 BC\4\F\4\ " IR BB 7 IR24*5/DV85 BC\4\F\7\ Xa-7 IR BB 107 Toyo*5/DV85 BC\4\F\4\ " IR BB 207 M 23*5/DV85 BC\4\F\5\ " IR BB 8 IR24*5/PI231129 " xa-8 IR BB 108 Toyo*5/PI231129 " " IR BB 208 M 23*5/PI231129 " " IR BB 10 IR24*5/Cas 209 BC\4\F\6\ Xa-10 IR BB 110 Toyo*5/Cas 209 BC\4\F\5\ " IR BB 210 M 23*5/Cas 209 BC\4\F\6\ " IR BB 11 IR24*5/IR8 BC\4\F\4\ Xa-11 IR BB 111 Toyo*5/IR8 " " IR BB 211 M 23*5/IR8 " " =============================================================================== 1Toyo=Toyonishiki, M 23=Milyang 23. ===============================================================================For developing near-isogenic lines for bacterial blight resistance, a collaborative project between the Ministry of Agriculture, Forestry and Fisheries (MAFF) of Japan through the Tropical Agriculture Research Center (TARC) and International Rice Research Institute (IRRI) was initiated in 1981. We crossed all the donors with known genes for resistance (Ogawa 1987) to IR24, Milyang 23 and Toyonishiki. Respective hybrids were backcrossed at least 4 times using IR24, Milyang 23 and Toyonishiki as recurrent parents. The recurrent parents were selected on the basis of their susceptibility to all the known races of bacterial blight in Japan and Philippines. During the backcrossing program, progenies were evaluated for resistance using Philippine races at IRRI and Japanese races at TARC (Ogawa and Yamamoto, 1987). The near isogenic lines developed so far are listed in Table 1. We are continuing to backcross newly identified genes using three recurrent parents mentioned above. Seeds of near isogenic lines are available for distribution to scientists interested in investigations on this important disease of rice. Please write either to Dr. T. Ogawa at TARC or Dr. G. S. Khush at IRRI.
References
Ogawa, T., 1987. Gene symbols for resistance to bacterial blight. RGN 4: 41-43.
Ogawa, T., and T. Yamamoto, 1987. Selection of recurrent parents to develop near-isogenic lines resistant to bacterial blight of rice. JARQ 21: 65-69.