Abstract
Flowers, leaves and stems were severely rotted on common garden petunia, Petunia×hybrida Vilm., in a glass house in Tokyo Metropolis in August 1995. Flowers with water-soaked lesions at an early stage wilted and rotted. Calyces, stems and leaves developed water-soaked, dark-green lesions, then rotted. Whitish mycelia and monosporous sporangiola were produced on the rotten plants. Sporangiola of the pathogen, were also observed on subirrigation mats and fallen flowers. A fungus exclusively isolated from lesions produced white to pale yellowish brown mycelia with scattered monosporous sporangiola on PDA plates. Inoculations with sporangiola reproduced the symptoms on its original host as well as on garden pea and four-o'clock. The same fungus was reisolated from the inoculated plants. The fungus produced monosporous sporangiophores and monosporous sporangiola abundantly on PDA. Zygospores were produced in dual culture with an authentic mating type isolate of Choanephora cucurbitarum (Berkeley & Ravenel) Thaxter. The causal fungus was identified as C. cucurbitarum based on morphology and mating tests. The fungus grew on PDA plates at 10-40°C with an optimum at 30°C. This paper represents the first report of C. cucurbitarum on common garden petunia causing a disease referred to as Choanephora blight.
