Genetics of resistance in rice cultivars, Chugoku 45 and Java 14 to Philippine and Japanese races of bacterial blight pathogen

Abstract

In studies of resistance of rice cultivars (Oryza sativa L.) to bacterial blight (BB) of rice caused by Xalethomonas campestris pv. oryzae, results from different countries could not be compared with each other, since different cultivars and/or different bacterial races were used in each counry. Therefore, it was necessary to re-analyze key cultivars using a uniform set of races, and to compare the results of previous studies from each country. For this purpose, we initially tested the usefulness of the clipping method of inoculation for genetic analysis of resistence in rice cultivars to BB in Japan. There was no previous report on genetic analysis in Japan using the clipping method of inoculation. We then analyzed rresistance in Japanese differentials, Chugoku 45 and Java 14 using Japanese and Philippine races of BB under a collaborative project between the International Rice Research Institute (IRRI), Philippines and the Ministry of Agriculture, Forestry, and Fisheries (MAFF), Japan. The clipping method of inoculation was useful for genetic analysis of resistant cultivars. In addition, we found Chugoku 45, Zenith, Himekei 16, Ortiglia, Zenith G713, Amareriyo, X-46, and Chukei 314 carry the gene Xa-3 originally found in Wase Aikoku 3 while X-43 has an additional major gene which is different from the Xa-3. Cultivars Akishinomochi and Nakashin 120 appear to have minor genes for resistance. The results of genetic analysis at IRRI and at Tropical Agrlculture Research Center (TARO) show that Chugoku 45, Java 14 and Wase Aikoku 3 are resistant to Phillppine races 1, 2, 3 and 4 as. well as to Japanese races.