Abstract
In an incompatible combination of rice cultivar and blast fungus race, the rapid increase of peroxidase activity of rice leaves occured within 24hr after inoculation, while a little or no increase was observed in a compatible case at early stage of infection. However, sudden increase occured at 3-5 days after inoculation in a compatible combination and the activity exceeded that of an incompatible combination. These alteration of activities occured more rapidly in aged leaves. The highest activity was observed at the time of rapid lesion enlargement in compatible case. The isozymes activated by the infection were fixed, and no new isozyme specific to compatible or incompatible combination was detected. The distinct difference between both combinations was the time of increase started. The ample supplies of nitrogenous fertilizer reduced the degree of resistance to rice blast disease. However, peroxidase activities increased with the doses of N-fertilizer and the highest activity was observed at the highest dose, i. e., under the most susceptible condition. These results indicate that the increase of peroxidase activity is possibly the reflection of host cell collapse or physiological disorder and may not be directly involved in the resistance mechanism.
