Deterioration of rice grains and development of foul flavor during the storage are serious problems which reduce the quality of stored grains. Lipoxygenase (LOX) catalyzes the peroxidation of linoleic and linolenic acids to form hydroperoxides. The hydroperoxides are transformed into volatile compounds causing foul flavors, thus LOX is related to the formation of the volatile compounds. The absence of LOX enzymes in rice grains may alleviate the oxidative deterioration. Three isozymes, LOX-1, LOX-2 and LOX-3 were found in rice embryos and LOX-3 is the major component of the isozymes accounting for 80-90% of total LOX activities. We found one LOX-3 deficient variety, Daw Dam after a preliminary survey (Suzuki et al. 1993). To analyze the geographical variation for the gene for LOX-3 deficiency, 471 Asian varieties were assessed using monoclonal antibodies. As a result, 21 varieties were found to be LOX-3 deficient (Table 1) and among them 7 were heterozygous for the LOX3 locus. The deficient varieties originated from China, Vietnam, Laos, Thailand and Myanmar. It is evident that the LOX-3

deficient varieties are distributed in a limited number of Asian countries.