First report of brown patch on bristle basket grass in Iran

The symptoms of brown patch or Rhizoctonia blight on bristle basket grass (Oplismenus hirtellus) were observed in the summers of 1998 and 1999. The individual plant symptoms consisted of blighted spots, which gradually expanded to encompass the entire surface of the leaf. Affected grass areas had a diameter of approximately 1 m. Plants started to recover and resumed growth from the center of the patch outward, producing a ring pattern in the affected area. Dark brown sclerotia were abundantly produced on the diseased plants and in the soil. A multinucleate Rhizoctonia sp. was consistently isolated from blighted tissues. Based on colony and mycelial characteristics, the fungus was identified as Rhizoctonia solani, and the anastomosis group (AG) for all of these isolates was determined as AG 1 by anastomosis testing (Burpee & Martin, 1992 and 1996). On the basis of cultural and sclerotial characteristics, a subset of the isolates was determined as AG 1- IA (Burpee & Martin, 1996). The mean hyphal diameter of AG 1-IA isolates was 7.0 µm, and the mean number of nuclei was 6.4 per hyphal cell. The colony was light brown on potato dextrose agar after 2 weeks of growth, and dark brown sclerotia measuring 0.7 to 4 × 1 to 4.5 mm were abundantly produced on the medium. Cardinal temperatures for growth of this isolate were 10, 28, and 35°C (minimum, optimum, and maximum, respectively). The linear growth rate at the optimum temperature was 34 mm per day. Pathogenicity of the AG 1-IA isolate was confirmed by placing 8-mm disks taken from the margins of an actively growing colony on the leaves and sheaths of the host plant and pots were incubated in greenhouse conditions (25-28 ۫C temperatures and more than 90% relative humidity) for one week (Kim, 1996). Symptoms observed were the same as those in the field, and the fungus was reisolated from the blighted tissue. To our knowledge, this is the first report of brown patch disease on O. hirtellus in Iran.