Rhizopus fruit Rot Caused by Rhizopus oryzae on Strawberry

Rhizopus fruit rot was observed on strawberry fruit (Fragaria x ananassa Duchesne) grown in a glass greenhouse at the Gyeongsangnam-do Agricultural Research and Extension Services, Jinju, South Korea, from 2011 to 2013. Symptoms included water-soaking, rapid softening, and rotting. When these symptoms were left untreated, vigorous fungal growth was observed on the surface of infected fruits. Colonies on potato dextrose agar (PDA) at 30°C were white-cottony to brownish-black. Sporangia were globose, black, and 40–210 ㎛ in diameter. Sporangiophores were light-brown and 6–22 ㎛ in diameter. Sporangiospores were globose to oval, brownish, streaked, and 4–12 ㎛ in length. Columellae were light brownish gray, hemispherical, and 80– 120 ㎛ in diameter. To confirm the identity of the causal fungal pathogen, the complete internal transcribed spacer (ITS) ribosomal RNA gene region was amplified and sequenced. Based on these symptoms, mycological characteristics, pathogenicity tests on host plants, and molecular identification, the fungus was identified as Rhizopus oryzae Went & Prinsen Geerligs. This is the first report of Rhizopus fruit rot on strawberry caused by R. oryzae in Korea.