Abstract
Pathogenic bacteria were isolated from yellow-browning and rotting fruiting bodies of oyster mushroom (Pleurotus ostreatus), king oyster mushroom (Pleurotus. eryngii), lion’s mane mushroom (Hericium erinaceus) and winter mushroom (Flammulina velutipes) individually cultivated on sawdust medium using A-D3 selective medium. The bacteria isolated were all identified as Ewingella americana based on bacteriological characteristics and 16S rRNA gene analysis. Yellow-browning symptoms on pileus of oyster mushrooms were observed after inoculation by spraying the obtained bacterial isolate into culture bottle after removal of surface mycelia (called the Kinkaki treatment). Discolored fruiting bodies with signs of rot were detected in the culture bottles 4 days after Kinkaki treatment followed by incubation at 20℃ for 3days. The causative bacterium from the discolored fruiting bodies was re-isolated using A-D3 selective medium, thus fulfilling Koch's postulates. These results suggested that E. americana is widely distributed and causes discoloration and rotting of cultivated mushrooms in Japan. Spray inoculation with Pseudomonas tolaasii into culture bottles of oyster mushrooms induced brown spots on the pileus of fruiting bodies that differed from symptoms caused by E. americana. This is the first report confirming yellow-browning and rotting symptoms on oyster mushrooms in culture bottles by inoculation of E. americana or P. tolaasii prior to primordium formation.
