THE INTERACTION OF THE SOFT-ROT BACTERIUM PSEUDOMONAS-GLADIOLI PV AGARICICOLA WITH JAPANESE CULTIVATED MUSHROOMS

The mushroom soft rot bacterium Pseudomonas gladioli pv. agaricicola w as observed to cause pitting when inoculated onto tissues of several c ommercially important Japanese cultivated mushrooms. Scanning electron microscope studies demonstrated the sequential removal of hyphal wall layers, thereby exposing the chitin skeletal matrix, which in turn wa s degraded. A second type of damage typified by collapsed, shriveled, and in some cases lysed hyphal cells was also observed. Culture plate assays revealed that Pseudomonas gladioli pv. agaricicola produces chi tinase and this, coupled with earlier evidence of a beta-glucanase enz yme, accounted for the degradative ability of the pathogen. The gelati nous coating on the Pholiota nameko sporocarp appeared to confer resis tance to Pseudomonas gladioli pv. agaricicola attack. Petri dish coinc ubations with several cultivated mushroom species indicated the abilit y of Pseudomonas gladioli pv. agaricicola to inhibit mycelial growth o ver a large distance and suggested the presence of a toxin or toxins. Owing to its wide host range, Pseudomonas gladioli pv. agaricicola is considered as a potential threat, not only to the mushroom industry in Japan but also to the mushroom industry in other tropical/subtropical countries.