This article first appeared in TResearch magazine, Vol 8 (3) 2013, an official science publication of Teagasc (Irish Agriculture and Food Development Authority)

MushTV is a three-year EU FP7 project generating scientific information and technologies for the European mushroom industry. The MushTV Consortium is made up of 17 partners across all sectors of the industry and includes six grower associations, five compost companies and five research organisations in Ireland, Britain, Belgium, the Netherlands and Poland. The project is focussed on generating scientific information and technologies in the areas of disinfectants, disease diagnostics and biopesticides to deal with two important diseases affecting mushroom production. Trichoderma aggressivum is a fungus that causes compost green mould, which dramatically reduces mushroom yield, while Mushroom Virus X (MVX) disease is associated

with a complex of viruses that cause mushroom browning and poor quality crops. Both diseases can have quite severe effects if they infect modern, technologically advanced “bulk phase 3” compost facilities. Bulk phase 3 mushroom compost is produced in large tunnels of up to 200-400 tonnes. When it is ready to produce mushrooms, this very vulnerable, living,  product is ‘bulk-handled’, using automated winches and conveyors, and then transported in bulk to mushroom growers. Infections in bulk compost can go unnoticed, partly due to the high level of automation involved, and the sheer volume of compost being handled. This means that the pathogens can be widely dispersed around compost facilities and mushroom farms before either green mould or virus problems develop.

Halfway through the project term, good progress has been made by the research partners and the main achievements of the seven research areas are summarised below.

Alternative disinfectant products and methods Identification of alternative disinfectant products that are effective against T. aggressivum and MVX (which is carried by the mushroom itself - Agaricus bisporus) is a priority for the industry. A shortlist of products for evaluation was drawn up in consultation with the consortium and, under laboratory test conditions, spores of A. bisporus and T. aggressivum were killed by most disinfectants. However, when the organisms were within compost particles it was difficult to kill either A. bisporus or T. aggressivum. During the final year of the project, a technical factsheet will be prepared on the efficacy of disinfectants in killing Trichoderma and virus-infected Agaricus propagules on farms and compost facilities. It will give clear guidance on the best ways to achieve good disinfection of machinery and facilities. Information will also be given to industry through workshops, seminars and conference presentations.

MVX – characterisation and improved diagnostic tests Characterising the MVX viruses present in MVX-infected mushrooms is key to understanding this complex disease.

Sequencing and bioinformatic analysis has tentatively identified 17 viruses that fit into all of the 11 classes of virus described for fungi.

This suggests that A. bisporus has received viral infection on multiple occasions. It is unknown whether these have occurred historically or in recent times. Only one of these viruses, Mushroom Bacilliform Virus (MBV), has previously been fully sequenced. The remaining 16 viruses are new to science. This new genetic information will facilitate the development of sensitive QPCR diagnostic tests that will be made available to mushroom industry service-providers.

Progress has also been made in simplifying virus extraction from compost samples, which should enable diagnostic tests to be more reliable.

Volatile-based diagnostic method for T. aggressivum Being able to detect volatile organic compounds (VOCs) of T. aggressivum in infected compost would greatly improve control of compost green mould. Preliminary results indicate that VOC profiles from T. aggressivum-infected compost can be discriminated from healthy compost after 14 days of growth in bulk tunnels.

Data analysis is progressing. Ultimately, this research will lead to the development of a volatile-based diagnostic method to detect T. aggressivum in phase 3 compost. Such a piece of equipment will alert composters when there is a T. aggressivum infection in phase 3 tunnels. Composters can then take action to minimise the impact of a potential disease outbreak and focus their attention on more rigorous hygiene measures.

Reservoirs of T. aggressivum and MVX on mushroom facilities Identifying where reservoirs of T. aggressivum and MVX inoculum occur on compost and grower facilities highlights weaknesses in their hygiene measures. Pilot studies have been completed and critical locations were identified for sampling. Four composters and four growers have been surveyed, and samples were tested for T. aggressivum and MVX. Results were reported back to industry on a confidential basis. Further testing of farms and compost facilities are planned or underway. This information will help individual SMEs to be more informed of disease risks on their facilities.

Work on tracking the incidence and spread of MVX inoculum on mushroom facilities, before, during and after an outbreak, is just starting.

Biocontrol of mushroom pathogens using Bacillus subtilis Identifying new products to control mushroom diseases is a high priority as there is only one approved product available in most EU countries. Bacillus subtilis, a biocontrol agent, is therefore being evaluated. Results show that it has little effect on mushroom production but it was ineffective against both Mycogone (wet bubble) and T. aggressivum. Further work is ongoing to test it against pathogens causing dry bubble and cobweb disease. A second product, Natamycin, is also being evaluated. Should a successful disease control product be identified, the consortium will co-operate with any company that will support the registration of the product for use in Europe. A new, effective disease control agent would greatly reduce anxiety within the mushroom industry. A technical  factsheet on disease-control will be produced for any successful product identified.

Growth of T. aggressivum in bulk phase 3 tunnels In order to characterise the growth of T. aggressivum in bulkincubation tunnels, trials were conducted in experimental tunnels (1.8 tonnes), subdivided into vertical and horizontal sections. A T. aggressivum infection was introduced into the bottom left hand corner at the rear of the tunnel. During tunnel emptying (end of spawn-run), T. aggressivum was not generally visible in the tunnel.

However, yield from compost at the back of the tunnel (near infected area) was reduced by 100%, while compost from the front cropped normally. Further trials will involve mixing the compost to replicate the bulk-handling and transportation processes that occur at commercial bulk phase 3 facilities. This research is increasing our understanding of how T. aggressivum grows and is dispersed within the phase 3 compost system. Information from all the Trichodermarelated research areas above will be used to compile a technical factsheet for mushroom growers and composters. Information will also be given to industry through workshops, seminars and conference presentations.

Dissemination and training To date, a number of articles have appeared in the mushroom press in the various partner countries (Ireland, Britain, Netherlands, Belgium and Poland) and a public website for the project is available at http://www.mushtv.eu. The first major dissemination event was held in May at “Mushroom Days 2013”, the International Trade Show for the Mushroom industry in the Netherlands. A summary of results to date has also been given to the Polish Mushroom Industry at one of their Mushroom Conferences and it was also  given to the Irish and UK mushroom industries at the  Ireland and UK Mushroom Conference in Monaghan on October 17, 2013.

Acknowledgements

This research was funded by the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 286836 - MushTV.

CELU

Mushroom growers talk to Teagasc’s Helen Grogan at the MushTV stand during Mushroom Days 2013 in the Netherlands.