Soft Rot of Rhizopus oryzae as a Postharvest Pathogen of Banana Fruit in Korea

Soft rot on banana fruit caused by Rhizopus oryzae was identified for the first time in Korea. Colonies were white to light brown and formed numerous sporangiospores. Optimum temperature for mycelial growth was 30degrees C. Sporangia were globose and 30~200 microm. Sporangiophores were usually straight, 8~20 microm, and rhizoids usually in groups of 3~5. Columella were globose to sub-globose and 90~110 microm. Sporangiospores were sub-globose or oval and 4~10 microm. Based on its mycological characteristics, molecular analysis, and pathogenicity to host plants, this fungus was identified as Rhizopus oryzae Went & Prisen Geerligs. This is the first report of soft rot on banana caused by Rhizopus oryzae in Korea.

Occurrence of Stem Rot of Wild Aster (Aster koraiensis) Caused by Sclerotium rolfsii in Korea

A destructive stem rot of wild aster (Aster koraiensis) occurred sporadically some farmers' fields in Guman-myon, Kosong-gun, Kyongsangnam-do in 2000. One of the most severely infected field in Kosong showed 28.6 percent of infection rate. The fungus also caused stem or crown rot and systemic wilt or blight of the plants. White mycelium spread over stems and petioles of infected plants and sclerotia formed on the old lesions and near the soil surface. The fungus showed maximum mycelial growth around 30degrees C and did not grow under 5degrees C and over 45degrees C and mycelial width were 4.3~10.2 microm. Colony was white, usually many narrow mycelial stand in the aerial mycelium and formed clamp connection. Numerous sclerotia were formed on PDA at 30degrees C. The shape sclerotia were globoid and 0.8~3.0x0.9~3.4 mm in size. The fungus was isolated repeatedly from the infected tissues and confirmed its pathogenecity to wild aster and identified as Sclerotium rolfsii. This is the first report on the stem rot of wild aster caused by S. rolfsii in Korea.