No abstract

No abstract

Double-stranded RNA (dsRNA) has been isolated from Agaricus bisporus fruit bodies exhibiting a wide range of disease symptoms. The symptoms which occurred singularly or in combination included ; bare cropping areas on commercial beds (primordia disruption), crop delay, premature veil opening, off-or brown-coloured mushrooms, sporophore malformations and loss of crop yield. All symptoms were associated with loss of yield and/or product quality. Collectively, these symptoms are described as mushroom virus X (MVX) disease. The dsRNA titre was much lower than that previously encountered with the La France viral disease of mushrooms and a modified cellulose CF11 protocol was used for their detection. A broad survey of cultivated mushrooms from the British industry identified dsRNA elements ranging between 640 bp and 20.2 kbp; the majority have not previously been described in A. bisporus. 26 dsRNA elements were identified with a maximum of 17, apparently non-encapsidated dsRNA elements, in any one sample. Three dsRNAs (16.2, 9.4 and 2.4 kbp) were routinely found in mushrooms asymptomatic for MVX. Previously, La France disease was effectively contained and controlled by minimising the on-farm production and spread of basidiospores. Our on-farm observations suggest that MVX could be spread by infected spores and/or mycelial fragments.

Substrates for mushroom cultivation were prepared, following a 2 day mixing and blending process, in bulk tunnels under a controlled temperature regime using forced ventilation. The temperature regime was based on a conventional bulk tunnel composting process, i.e. pasteurization at 60 °C for 6 h, followed by a conditioning phase at 47 °C until the substrate was clear of ammonia. With the exception of ammonia, which increased with increasing compost nitrogen content, this process did not result in strong odours. The substrates were ready for inoculation with mushroom 'spawn' 7-12 days after the initial mixing of the compost ingredients. Increasing the compost nitrogen content from 11 to 2-5% of the dry matter by increasing the quantity of deep litter poultry manure added to straw in the ingredients resulted in a greater subsequent yield of mushrooms. Further increases in the substrate nitrogen content resulted in prolonged tunnel processing times, substrate desiccation, incomplete clearance of ammonia from the substrate and subsequently low or no mushroom yields. Substrate bulk density at the time of spawning decreased with increasing nitrogen content, but was increased by chopping the straw ingredient. Mushroom yields from composts prepared with barley straw were significantly lower than those from wheat straw composts, at equivalent nitrogen contents. Supplementation of prepared substrates with the proprietary protein-rich ingredient, Betamyl 1000, increased yields by 136%.

No abstract