Occurrence of false smut (Ustilaginoidea virens) in rice field of Mazandaran.
Symptoms of large, black, ball-shaped grains on panicles of several rice cultivars (Khazar, Nemat, Neda) were observed in August 1997 in a village of Bandpai-Sharghi district, Otagh-Sara of Babol, Mazandaran, Iran. It was noted that only a few grains were usually infected in each panicle, with the other grains smaller than those in healthy panicles. Infected grains were yellowish-orange initially, turning olive green and then black. Each infected grain contained chlamydospores, 4-7 μm diameter. The causal agent was identified as Ustilaginoidea virens; this is a new record for the mycota of Iran. This disease was not observed on any other plants (Poaceae) in the infested area.