Evidence for the association of the enteric bacterium Ewingella americana with internal stipe necrosis of Agaricus bisporus

Abstract

Internal stipe necrosis of Agaricus bisporus is recognized as an emerging and potentially serious disease in the UK mushroom industry. Symptoms are visible only on harvest and appear as a variable browning reaction in the centre of stipes, which may be accompanied by limited collapse of the internal tissues.The hypothesis that this problem is of bacterial origin was investigated, initially by an extensive bacteriological examination of affected mushrooms.The enteric bacterium €winge//a americana was isolated from a t least 93% of symptomatic mushrooms. Various strains of Pseudomonas fluorescens are also usually present in diseased mushrooms, but no single P. f/uorescens biovar was consistently associated with the disease. Typical symptoms were reproduced following infection trials with isolates of E. americans derived from diseased mushrooms. In addition, strains recovered from diseased mushrooms following such trials were shown by RFLP studies to be identical to those applied, thereby confirming Koch's postulates for these strains. The possible contribution of other bacterial species to symptom development is discussed.

Cloning of a chitinase gene from Ewingella americana, a pathogen of the cultivated mushroom, Agaricus bisporus

“…Ewingella americana has been shown to be associated with a browning disorder of the stipe of the mushroom Agaricus bisporus, called internal stipe necrosis (Inglis et al, 1996). Chitin is a vital component of the cell walls of the majority of fungi (Cabib, 1987).…”

The General Secretory Pathway of Burkholderia gladioli pv. agaricicola BG164R Is Necessary for Cavity Disease in White Button Mushrooms

“…americana PRC120 is the first report of a New Zealand isolate of E. americana from mushrooms, and it has been deposited in the New Zealand Culture Collection (accession number of NZRM 4225). Interestingly, PRC120 isolated from button mushrooms in New Zealand did not cause any necrotic symptoms (17,18) in our assay.…”

“…Moquet et al (25) in their study of blotch disease observed a species-specific difference in symptom intensity to disease caused by P. tolaasii. Inglis et al (18) mentioned a variation in the intensity of disease symptoms by E. americana and reported an interaction between P. fluorescens and E. americana in the formation of internal stipe necrosis of mushrooms. They also suggested a contributory role played by P. fluorescens in the expression of disease symptoms.…”

“…Possibly E. americana prevents B. gladioli from reaching the necessary population density to cause symptoms, either passively through resource competition or actively by expression of a toxin. Other mushroom diseases, such as brown blotch caused by Pseudomonas tolaasii (25) and internal stipe necrosis caused by E. americana (18), require a very high number of cells (ϳ10 8 ) for their initiation under test conditions. Thus, either quantitative or qualitative differences in the native flora from mushroom to mushroom may account for all or some of the variability in the disease.…”

“…Strain CANU-PMS164 rapidly degraded mushroom sporocarps, which resulted in marked tissue damage within 72 h of infection. Although cavity disease was originally thought to be a novel disease (18), it was later reclassified (as reported by Gill and Tsuneda [14]) as "rapid soft rot disease of edible mushroom." The causative agent was subsequently renamed Pseudomonas gladioli pv.…”