Epsilon Archive for Student Projects

Abstract

Oomycetes causing root disease are a big problem in horticulture and agriculture. These diseases
are especially problematic in organic cultivation where pesticides are not a possible option for
disease control. As a potential solution to this problem, spent mushroom compost was evaluated.
Spent mushroom compost (SMC) is a by-product of commercial production of mushrooms with
potential to be used in cultivation for plant nutrition and disease suppression.
The current study used water extract from spent mushroom compost obtained from either button
mushroom (Agaricus bisporus) or oyster mushroom (Pleurotus ostreatus) as a strategy to supress
the occurrence of oomycete disease in dill cultivation. The oomycetes were isolated from organic
dill plants cultivated by a commercial producer. The potential of water extract towards disease
suppression were investigated In vitro and In vivo experiments in different proportions, diluted by
either water or vegetable juice (100:0%, 70:30%, 50:50%, 30:70%, 0:100%). Suppression of
oomycete growth by SMC water extract was investigated In vitro in dual culture tests on agar plates
and as mycelial growth in liquid V8. In vitro development of disease symptoms on roots was also
investigated. To confirm results from the In vitro trials an In vivo experiment was performed. For
the In vivo trial, dill seeds were sprouted on healthy soil with and without amendment of either
oomycete suspension or water extracts. Infected soil was also used to test the if soil inoculated with
oomycetes could be reused for cultivation.
Overall, SMC from both A. bisporus and P. ostreatus showed suppressive potential. Pure SMC
(100% amendment) lowered the viability and the mycelial growth of the oomycete in both In vitro
and In vivo investigations. Diluted water extracts had also the potential to supress the oomycetes
growth and disease severity. However, the amendment of 100% SMC water extract indicated the
most effective disease control strategy compared to other proportions. On infected soil In vivo, 100%
amendment of SMC from A. bisporus lowered oomycete growth but did not enhance the seed
germination.
SMC displays potential for being used as a suppressant of oomycete disease in dill cultivation.
The use of water extract from SMC against oomycetes could reduce use of harmful and expensive
pesticides and open up for enhanced sustainability in organic farming. Before wide use, quantity,
dilution, and conditions interacting with SMC In vivo needs to be further evaluated.