Abstract:
Mushroom is widely cultivated as a protein rich vegetable in many countries of the world including
Kenya. However, a number of harmful fungi are encountered and many of these act as competitor
moulds thereby adversely affecting spawn-run, whereas others attack the fruiting bodies at various
stages of crop growth producing distinct disease symptoms. Management of mushroom diseases
and contaminants is complicated by the high restriction on the number of accepted pesticides. In
addition, the pesticides may be harmful to human health and the environment, and are expensive
to small scale farmers. The use of biocontrol agents provides an alternative to replace the existing
synthetic pesticides. The aim of this study was to test antimicrobial activity of antagonistic
bacteria, selected fungal endophytes and Engleromyces goetzei against mushroom pathogens and
contaminants and their effects on mushroom mycelia. Phytochemicals present in E. goetzei were
extracted by use of soxhlet apparatus, tested and identified as steroids, terpenoids, saponins,
flavonoids and coumarins. The antimicrobial assays were conducted using the dual culture method
where a 5 mm plug of actively growing pathogen/contaminant was inoculated on one end of a
PDA plate and the plate was doubly inoculated with the antagonist. Colony growth of mushroom
pathogens and contaminants in the dual plates were recorded and percentage inhibition calculated
in relation to plates with pathogens alone which served as controls. All the experiments were done
twice in completely randomized design (CRD) with five replicates. Data was subjected to analysis
of variance (ANOVA) using SAS statistical package. Mean values of all treatments were tested
for significant differences and separated using LSD. Endophyte LAF 59 (Laggera alata fungus)
exhibited the strongest inhibitory activity with 76% inhibition of the mycelial growth of
Penicillium digitatum, 46.5% for Aspergillus flavus and 65.8% for A. parasitica. The percent
inhibition induced by B. amyloliquefaciens was 76% against Trichoderma harzianum, 79.1%
against T. asperellum, 80.3% against Aspergillus sp., 82.4% against Penicillium sp., 75.6% against
Mucor sp. and 65.3% against Rhizopus sp. Volatile organic compounds produced by Bacillus
amyloliquefaciens were also effective against the pathogens tested. These results indicate that B.
amyloliquefaciens and the bioactive endophytic fungi LAF 59 and LAF 13 can be suggested as
important alternatives to reduce fungicide application in the control of mushroom diseases and
contamination.
