Mushroom Virus X disease
Outbreaks of mushroom virus X (MVX) occur each year. Economic consequences include yield losses, delayed cropping and reduced mushroom quality (brown, discoloured and distorted mushrooms). MVX is a complex of RNA viruses; at least 30 RNA molecules have been separated by gel separation, but these are currently poorly understood and characterised. EMR is engaged in two projects to characterise the viruses and understand how they move both within the cell and between farms. These are funded by Walsh Fellowship, by Teagasc (Ireland) and a European Union FP7-funded project entitled “MushTV” in collaboration with 16 research and industry partners across Europe, including all major mushroom composters and growers in Ireland, Britain, The Netherlands, Belgium and Poland.
Two genomic technologies are being used: microarrays to examine host (A. bisporus) interactions with MVX and Next Generation Sequencing (NGS) to sequence and thus identify all of the viruses. The microarray work has shown that the effects of MVX on A. bisporus transcription vary depending on tissue; 32% of genes from mycelia growing on compost change upon MVX infection compared with 15% and 0.7% of genes from mycelia growing on casing or from mushrooms respectively. A large proportion of the nutritional genes in the mycelium growing compost are down-regulated upon MVX infection, i.e. those encoding enzymes for the breakdown of polymers (cellulose, hemicellulose and lignin).
A highly-sensitive detection methodology for MVX is key for understanding how the disease moves within and between farms and as an early-warning system. A PCR-based test has been devised to detect two of the viruses in compost samples; however, this is costly due high purification costs to render RNA free from any humic contamination. The Mush-TV project is working to improve this test so as to be able to detect all of the viruses (using sequence information from NGS work) and to improve extraction technology of RNA from compost.