A rust on Asiatic dayflower plant (Commelina communis L.) was found in Geoje, Korea, in August 2010. Uredia are mostly produced on abaxial leaf surface or elongated on stem, early naked, surrounded by the ruptured epidermis, cinnamon-brown. Uredospores are globose, ellipsoid or ovate, echinulate, yellowish brown or brown, 20-30 × 20-25 ㎛. On the basis of mycological characteristics and molecular data, the fungus was identified as Uromyces commelinae Cooke. The phylogenetic position of U. commelinae is separate from the other rusts where the economically important rusts of the Poaceae are situated. Although host ranges of the rust caused by U. commelinae were previously recorded, full descriptions and illustrations, including symptoms and signs have not been described. This is the first description of rust disease on C. communis plant with molecular identification, symptoms, and signs.

• Jin-Hyeuk Kwon(Gyeongsangnam-do Agricultural Research and Extension Services)
• Jinwoo Kim(Division of Applied Life Science (BK21 Plus), Gyeongsang National University, Institute of Agriculture and Life Sciences, Gyeongsang National University) Corresponding author