Rhizopus Fruit Rot Caused by Rhizopus oryzae on Strawberry

Abstract

Rhizopus fruit rot was observed on strawberry fruit (Fragaria x ananassa Duchesne) grown ina glass greenhouse at the Gyeongsangnam-do Agricultural Research and Extension Services,Jinju, South Korea, from 2011 to 2013. Symptoms included water-soaking, rapid softening, androtting. When these symptoms were left untreated, vigorous fungal growth was observed on thesurface of infected fruits. Colonies on potato dextrose agar (PDA) at 30°C were white-cottonyto brownish-black. Sporangia were globose, black, and 40–210 ㎛ in diameter. Sporangiophoreswere 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 internaltranscribed spacer (ITS) ribosomal RNA gene region was amplified and sequenced. Based onthese symptoms, mycological characteristics, pathogenicity tests on host plants, and molecularidentification, the fungus was identified as Rhizopus oryzae Went & Prinsen Geerligs. This isthe first report of Rhizopus fruit rot on strawberry caused by R. oryzae in Korea.