Abstract:
Green mould is a serious disease of commercially grown mushrooms, the causal agent
being attributed to the filamentous soil fungus Triclzodenna aggressivum f. aggressivu11l
and T. aggressivum f. ellropaellm. Found worldwide, and capable of devastating crops,
this disease has caused millions of dollars in lost revenue within the mushroom industry.
One mechanism used by TricllOdenlla spp. in the antagonism of other fungi, is the
secretion of lytic enzymes such as chitinases, which actively degrade a host's cell wall.
Therefore, the intent of this study was to examine the production of chitinase enzymes
during the host-parasite interaction of Agaricus bisporus (commercial mushroom) and
Triclzodemza aggressivum, focusing specifically on chitinase involvement in the
differential resistance of white, off-white, and brown commercial mushroom strains.
Chitinases isolated from cultures of A. bisporus and T. aggressivu11l grown together
and separately, were identified following native PAGE, and analysis of fluorescence
based on specific enzymatic cleavage of 4-methylumbelliferyl glucoside substrates.
Results indicate that the interaction between T. aggressivulll and A. bisporus involves a
complex enzyme battle. It was determined that T. aggressivum produces a number of
chitinases that appear to correlate to those isolated in previous studies using biocontrol
strains of T. Izarziallilm. A 122 kDa N-acetylglucosaminidase of T. aggressivu11l revealed
the highest and most variable activity, and is therefore believed to be an important
predictor of antifungal activity. Furthermore, results indicate that brown strain resistance
of mushrooms may be related to high levels of a 96 kDa N-acetylglucosaminidase, which
showed elevated activity in both solitary and dual cultures with T. aggressivum.
Overall, each host-parasite combination produced unique enzyme profiles, with the
majority of the differences seen between day 0 and day 6 for the extracellular chitinases.
Therefore, it was concluded that the antagonistic behaviour of T. aggressivli1ll does not
involve a typical response, always producing the same types and levels of enzymes, but
that mycoparasitism, specifically in the form of chitinase production, may be induced and
regulated based on the host presented.
