1990 Volume 56 Issue 1 Pages 26-32
To reveal the relationship between the resistance to rice blast disease on rice plants and the amount of oxygenated C-18 unsaturated fatty acids isolated from rice plant as anti-blast substances, the change of the activity of lipoxygenase (LOX) which participates in the synthesis of these compounds in rice leaves was investigated. Although LOX activity in rice leaves was sensitive to the water-spraying resulted in a little increment, it has been clearly and largely enhanced by blast infection. The pattern of change in LOX activity with days after inoculation depended on the combination of rice cultivar and the race of rice blast fungus. In rice leaves shown incompatible reaction, LOX activity increased rapidly from the first day of spray-inoculation and reached to the maximum two or three days after, and declined thereafter. In the compatible combination, the highest activity was observed seven days after inoculation, although LOX activity rose temporarily in two or three days. Rice cultivars having higher level of field resistance showed higher LOX activity than that with low level of it. In addition, LOX activity in mature leaves was also greater than that of the just expanded young leaves of all cultivars examined.