Rarity of on Edible Mushrooms Associated with Susceptibility to Biological Competition.

Taxonomically diverse species induce bacterial blotch of edible mushrooms around the world. , [. ], and are dominant mycopathogenic pseudomonads in mushroom production farms. In this study, among 216 mycopathogenic bacterial strains isolated from edible mushrooms in Iran, 96 strains were identified as spp., while only three strains were preliminarily identified as . Multilocus sequence analysis showed that only one strain (FH2) authentically belonged to , while the other two strains either belonged to [] or represented a unique phylogenetic clade. The three strains also differed from each other in phenotypic characteristics, for example, production of fluorescent pigment and the reaction to tolaasin produced by . Pathogenicity assays under a controlled environment showed that the symptoms induced by authentic were far less severe than those caused by the predominant species . Furthermore, coinoculation of with three bacterial pathogens that are prevalent in Iran on mushroom caps, that is, , , and sp., resulted in the development of combined symptoms representing characteristics of both pathogens. The antibiosis assay showed that tolaasin-producing strains of could inhibit the growth of , while tolaasin-negative strains of the same species were unable to do so. This led us to the hypothesis that the inhibitory effect of on is driven by tolaasin production in the former species. This inhibitory effect is also associated with the rarity of in natural conditions.