On the Effect of Sunlight upon the Development of the Helminthosporium Disease of Rice

Abstract

1. The present paper deals with the results of experiments on the effect of sunlight upon the infection of the rice plant by Ophiobolus Miyabeanus, to the germination of its conidia and also to the disease-development.2. Rice seedlings are more abundantly infected in the absence of light than in the presence of light.3. The percentage of conidial germination of the causal fungus and also the length of its germ-tubes are greater in the absence of light than in the presence of light.4. Using four glass boxes kept under the same conditions except light intensity, the writer has carried out an experiment on the effect, upon the development of the disease, of shading after inoculation. The number of diseased lesions per unit length of the leaf was maximum on the seedlings kept in the box covered with two sheets of cotton cloth and minimum on those in the box covered with black paper. The seedlings, kept in the boxes uncovered or covered with a single sheet of cotton cloth, showed the medium number of lesions.5. Using the same boxes, the writer carried out an experiment on the effect, upon the disease development of rice seedlings, of shading before inoculation. The number of diseased lesions per unit length of the leaf was maximum on the seedlings kept in the box covered with a single sheet and minimum on those in the box covered with two sheets of cotton cloth. The seedlings, kept in the boxes covered with black paper or uncovered, showed the medium number of lesions.