Studies on the Relationship between Inoculum Concentration and Disease Development in Bacterial Leaf Blight of Rice

The study has been carried out for the development of an inoculation method in screening resistant varieties and/or lines to bacterial leaf blight of rice with special consideration on plant ages and inoculum concentrations. A higher incidence of the disease was found on younger plants than on the older ones when the plants were inoculated with the same concentration of inoculum by clipping method under the same circumstances. Applications of extremly high concentration of inoculum resulted the death of younger seedlings from all varieties within short period after inoculation, and the inoculum that was lower than optimum concentration failed in distinguishing varietal characteristics in regard of resistance. The proper inoculum size for the screening of resistance among the varieties and/or lines depended on the age of plants. The optimum concentration of inoculum for the plant age of 14, 37, 48 and 58days was respectively.