Volume 19 Part 1 Article 29: The Influence of the Pleurotus Substrate Microbial Colonisation on the Growth of Trichoderma pleuroti

Volume 19 Part 1 Article 29
Year 2016
Title: The Influence of the Pleurotus Substrate Microbial Colonisation on the Growth of Trichoderma pleuroti
Author: Ivan Jablonský, David Novotný, Rudolf Ryzner, Milan Gryndler

Currently, the biggest problem in Pleurotus ostreatus growing in the Czech Republic is an adverse effect of Trichoderma pleuroti infection. The purpose of this work was (i) to identify possible sources of the contamination in a compost yard and a mushroom farm, (ii) to uncover the influence of the selected factors on the growth of T. pleuroti and (iii) to prepare the substrate resistant to the T. pleuroti infection. We used various combinations of the treatment (the natural outside fermentation of the straw, the temperature treatment of the substrate, and the addition of a lime component) and studied their effect on the growth of P. ostreatus and T. pleuroti and the changes in the microbiome of the substrate.

Surprisingly, we didn’t identify T. pleuroti in the air of the compost yard and the oyster mushroom farm and therefore we focused our attention on the substrate. We observed that T. pleuroti developed faster in the sterilized substrate than in the substrate subjected to heat treatment of 60-70 °C. Moreover, sa straw infected with T. pleuroti, subsequently fermented (30 °C, 36 hours) and then steamed (60, 65 or 70 °C) was completely colonized with mycelium of P. ostreatus, whereas, on the straw infected and steamed without the fermentation procedure, we observed the development of T. pleuroti.

We also compared the Pleurotus substrate samples subjected to the short straw fermentation at different temperatures which were steamed for 24 hours at 70 °C with and without the addition of the lime component. In these samples, bacterial and fungal operational taxonomic units (OTUs) were identified on a DNA level using the 545 pyrosequencing. The majority of the bacterial sequences belong to OTUs corresponding to Paenibacillus and Bacillus species and the most frequent fungal OTUs correspond to Wallemia and Verticillium spp. All these OTUs were more abundant in the samples after steaming (70 °C) than without steaming. Contrary to the temperature of the fermentation, the addition of the lime component had no significant effect on the composition of the microbiome.

We can conclude that the pre-fermentation of the straw can inhibit the growth of T. pleuroti. We also found that the substrate treatment at 70 °C does not cause the decrease in microbial growth; right the opposite: it can support particular bacterial and fungal species development, which subsequently leads to the higher resistance of the substrate against T. pleuroti infection.

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