Pod Rot of Cowpea (Vigna sinensis) Caused by Choanephora cucurbitarum

In August 2001, pod rot of cowpea caused by Choanephora cucurbitarum was found in the experimental fields of the Gyeongsangnam-do Agricultural Research and Extension Services, Korea. Initial symptoms of the disease were the appearance of water-soaked, dark-green lesions and followed by rapid rotting of the infected tissues. As the disease progressed, whitish mycelia and monosporous sporangiophore with monosporous sporangiola were produced on the lesions. The fungus produced white to pale yellowish brown mycelia with scattered monosporous sporangiophore and monosporous sporangia containing sporangiospores on potato dextrose agar (PDA). Monosporous sporangiophore was long, slender and branched at the apex, with each branch bearing a sporangiospore. Sporangium was subglobose in shape and 42.6-112.6 ㎛ in size. Monosporous sporangiola were elliptic, fusiform or ovoid, brown in color, and 9.8-23.4$\times$7.2-12.8 ㎛ in size. Sporangiospores were elliptic, fusiform or ovoid in shape, dark brown or brown in color, 12.9-24.6$\times$8.6-15.4 ㎛ in size, and had three or more appendages. Zygospores were black and 43.6-72.4 ㎛ in size. The fungus grew on PDA at 15-40$\^{C}$, and optimum temperature was 30$\^{C}$. This is the first report on pod rot of cowpea caused by C. cucurbitarum in Korea.