Inoculation with conidiospores of false smut fungus to rice panicles at the booting stage.

Abstract

To establish the effective method for inoculating the false smut fungus, Ustilaginoidea virens, to rice plant, the injecting or the spraying inoculation method was attempted by using suspension of conidiospores produced on potato sucrose agar medium. About 2 ml of conidial suspension was injected into the leaf sheath of rice plant at the booting stage. The inoculated plants were placed in an air conditioning room (Koitotron S types) for 2 days at 15 C, and then incubated in a moist chamber for 5 days at 26 C. After incubation, these plants were kept in a green house (25-35 C) until smut balls appeared. The results obtained here seemed to indicate that the false smut disease was favored by low temperature (15 C) and high humidity (100%) for infection, and by a relatively high temperature (25-35 C) for appearance of the disease symptom. The successful results of inoculation were also obtained by means of spraying with a conidiospore suspension onto the rice plants in field. The proper time for inoculation seemed to be 10-30 days before heading of rice. This is the first report on the infection of the false smut by inoculation with conidiospores.