Root invasion of rice seedlings by Ustilaginoidea virens

In recent years, false smut disease of rice caused by Ustilaginoidea virens has emerged a disease of concern to rice in all over the world. There is always a controversy about whether the pathogen can infect the rice root and causes false smut disease. In the present investigation, we studied the invasion of roots of rice seedlings by U. virens. Initial infection of roots of rice seedlings by U. Virens was incited using axenically cultured chlamydospores (2*10⁵ conidia/ml). These chlamydospores were observed on surface of rice roots at 1 day post inoculation (dpi), which germinated 1–5 dpi. At 7 dpi, the infection germ tube was observed to be invading the intercellular space between epidermal rice root cells. Between 13 and 15 dpi, branching and fusion-like structures were observed that may contribute to the development of the hyphal network on the root surface. The results showed that the chlamydospores could attach to the surface of young roots and penetrate into the intercellular space of the rice root epidermis but does not cause further invasion in rice.