Bacillus velezensis in Button Mushroom Farming: Impact on Crop Health and Yield

Button mushrooms (Agaricus bisporus) represent a cornerstone of the mushroom industry. Cultivating them successfully hinges on overcoming various challenges, including their susceptibility to pathogens, nutritional deficits in the cropping system, and unwanted fluctuations in growth conditions. Bacillus velezensis is a Gram-positive, spore-forming bacterium, renowned for its versatile capabilities in plant agriculture – this bacterium has already garnered significant attention for its potential to promote plant growth, suppress plant pathogens, and improve soil health. Within the context of button mushroom farming, Bacillus velezensis is also emerging as a potential key player with significant implications for crop health and yield.

The potential role of Bacillus velezensis in mushroom farming

Disease Suppression

Button mushrooms are susceptible to a range of pathogens, with fungal diseases including green mould (Trichoderma), cobweb (Cladobotryum), wet bubble (Lecanicillium), and dry bubble (Mycogone) each posing a substantial threat (Microorganisms | Control of Fungal Diseases in Mushroom Crops while Dealing with Fungicide Resistance: A Review). These pathogens can affect mushrooms directly, but many strains act more simply as competitive microorganisms, competing for any available nutrition subsequently reducing crop yields. Bacillus velezensis is known to produce a suite of secondary metabolites – molecules which are often secreted from bacteria which aid in aspects such as growth and colonisation. Some of these metabolites are also known for their inhibitory effects against competitor microorganisms. Future aims for the industry could be to use strains of B. velezensis which are ‘super-producers’ for specific antimicrobial compounds, or (less directly) to harness the ability of the microbe to produce antibiotic compounds in large scale fermenters which could then be used directly as bio-pesticides. Finding alternative methods to traditional fungicides is particularly important in the face of recent EU wide bans on many previously available fungicidal options.

Nutrient Uptake Enhancement

Agaricus bisporus mycelium relies on efficient nutrient absorption for growth and fruiting body formation. Nutrients in the cropping environment are limited, as many (particularly micronutrients), are in forms which are unavailable to the growing crop. Bacteria such as Bacillus can be proficient in converting these nutrients (such as Potassium, Iron, Phosphorus) from insoluble/unavailable forms, to forms which can be taken up by Agaricus, thus boosting the potential yield of crops (The Endophytic Bacteria Bacillus velezensis Lle-9 harbours Plant Growth-Promoting Effects). Additionally, many bacterial strains can produce enzymes which help to break down organic matter found within the mushroom growth medium (compost) to free up more nutrients for the growth of the mushroom crop – thus some bacterial strains may also be able to contribute to button mushroom farming sustainability by allowing for a more ‘complete’ nutrient acquisition by Agaricus during the cropping cycle.

Stress Tolerance Mechanisms

Although mushroom growth rooms are often rigorously controlled, environmental factors including temperature and humidity fluctuations can significantly influence cultivation. Bacillus velezensis has been cited as being successful at promoting plant growth in stress conditions such as excess heat, cold/freezing or drought stress (Bacillus velezensis 5113 Induced Metabolic and Molecular Reprogramming during Abiotic Stress Tolerance in Wheat – nature.com). The mechanisms by which this is achieved in plants may also protect Agaricus from unwanted fluctuations in the growing cycle, thus enhancing crop resilience and promoting the growth of mushrooms under imperfect conditions.

Sustainability in button mushroom farming is vital – by reducing reliance on chemical inputs and promoting ecological balance through natural biological processes, Bacillus velezensis offers potential for a sustainable solution to ongoing issues with pathogens, nutritional deficiencies, and fluctuations in growth conditions. Ongoing research at the BIOSCHAMP project endeavours focus on optimizing its integration into button mushroom farming practices to foster long-term environmental and economic sustainability.