'Drippy gill' : An ooze disease of the cultivated mushroom Agaricus bisporus caused by Pseudomonas agarici

摘要

'Drippy gill', a serious bacterial disease of cultivated mushrooms, was investigated. The causal organism, Pseudomonas agarici, causes profuse ooze from the gills of affected sporocarps and intrahyphal transmission was suspected. However, the majority of bacteria were shown to occur extrahyphally with only occasional intrahyphal presence. Enzymatic and developed gold labelling techniques showed P. agarici was essentially unable to actively penetrate fungal hyphae. In the presence of P. agaric; cells, the extrahyphal matrix was actively degraded as were the outer fungal wall layers. P. agarici was shown not to produce chitinase, however, β-glucanase activity was evidenced by dissolution of the extracellular matrix and glucan of the Agaricus hyphal wall. Unlike most other fluorescent pseudomonads of the mushroom casing layer, both P. agarici and PV29 did not readily show transformation of the smooth wild type colony form to the rough variant. The unique features of the 'drippy gill' organism such as lack of toxin production and the ability to penetrate Agaricus protective membranes are discussed and an epidemiology of 'drippy gill' disease forwarded. A new mushroom disease, 'cavity-cap', was recorded and the causal organism identified as P. cepacia (later re-classified as P. gladioli var agaricicola).