O'Brien, Matthew
(2012)
Molecular and Epidemiological Studies of
Trichoderma aggressivum f. europaeum.
PhD thesis, National University of Ireland Maynooth.
Abstract
Trichoderma aggressivum is the causal agent of severe green mould disease in the
cultivated mushroom Agaricus bisporus (Samuels et al., 2002). This fungus was
First isolated in Ireland in 1987 during an epidemic of green mould disease and
has subsequently been isolated from mushroom farms across Europe and North
America (Largeteau et al., 2010). There are two subspecies T. aggressivum f.
aggressivum and T. aggressivum f. europaeum which are found in North America
and Europe respectively, the latter is the subject of this work.
The purpose of this study was to investigate the interaction of T. aggressivum
with A. bisporus and mushroom substrate, to study the epidemiology of T. ag-
gressivum in Bulk Phase III mushroom systems and to develop methods for the
detection of T. aggressivum. A separate results chapter is presented for each area
of research.
T. aggressivum has specific attributes which allow it to grow better in mushroom
substrate than other Trichoderma species, resist inhibition by A. bisporus
metabolites and ultimately cause more severe reductions in mushroom yield
(Largeteau et al., 2000b; Mumpuni et al., 1998). A proteomic method was employed
to study the effect of mushroom substrate and A. bisporus tissue on T.
aggressivum in vitro. Proteins involved in the oxidative stress response were upregulated
in T. aggressivum in both treatments. In vivo the production of oxidative
stress response proteins may be part of the ability of T. aggressivum to resist
inhibition by the microbial population of mushroom substrate and by A. bisporus,
thereby colonising the substrate and reducing mushroom yields (Largeteau et al.,
2000b; Savoie et al., 2001a; Williams et al., 2003a).
Much of the research on the epidemiology of T. aggressivum in mushroom
production was performed in in situ spawn run systems. The Bulk Phase III
system has become more common in Europe in recent years but there is little
information about T. aggressivum in this system. Cropping experiments were
carried out to investigate the epidemiology of T. aggressivum in Bulk Phase III
with particular emphasis on the effect of bulk handling of spawn-run substrate on
infection. Infection of Bulk Phase III substrate during bulk handling was shwon
to be possible. The severity of infection depended on T. aggressivum load and
on the amount of mixing performed during bulk handling.
Identification of T. aggressivum can be problematic due to morphological similarities
with Trichoderma harzianum and other Trichoderma species found on
mushroom farms (Seaby, 1996a). The most common method for differentiating
T. aggressivum from other species is the of PCR (Chen et al., 1999a) with selectve
primers. In this study a real-time PCR method for identification of T.
aggressivum was developed, novel selective primers were designed and compared
to existing T. aggressivum selective primers and HPLC analysis of secondary
metabolite profiles was assessed as an alternative method for the identification of
T. aggressivum.
| Item Type: |
Thesis
(PhD)
|
| Keywords: |
Agaricus bisporus; Bulk Phase III; green mould disease; proteomics; real-time PCR; Trichoderma aggressivum; |
| Academic Unit: |
Faculty of Science and Engineering > Biology |
| Item ID: |
5676 |
| Depositing User: |
IR eTheses
|
| Date Deposited: |
14 Jan 2015 14:53 |
| URI: |
|
| Use Licence: |
This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available
here |
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