Sporulation, Inoculation Methods and Pathogenicity of Ustilaginoidea albicans, the Cause of White Rice False Smut in China

Sporulation and inoculation methods were studied to determine the pathogenicity of Ustilaginoidea albicans S Wang and JK Bai, the cause of white rice false smut, isolated in China. High sporulation was obtained using solid culture, liquid fermentation and double layer incubation system. In liquid culture, the culture media composition contributed to observed differences in sporulation. Potato sucrose broth was the optimal media to promote conidia production, increasing the concentration to up to 4.8 × 108 spores/ml. Inoculation by injection and spraying resulted in disease development, demonstrating that conidia of white rice false smut are virulent to rice plants, despite apparent differences in disease incidence. Estimates of mean disease severity were higher for injection than for spraying as assessed by percent infected panicles. The two methods resulted in disease severity ranging from 12.0 to 28.7% and 8.2 to 20.7%, respectively. Low temperature exposure after inoculation had a strong stimulatory effect on disease development.