Abstract
It has been reported that P. tolaasii S8501 isolated in Japan caused bacterial rot of oyster mushroom (Pleurotus ostreatus, Japanese name: ‘Hiratake’) and produced 8 kinds of toxin as pathogenic factor. Tolaasin I, the main toxin, plays an important role in the development of the symptom on the fruit bodies of ‘Hiratake’ and Flammulina velutipes (‘Enokitake’). P. tolaasii S8501 was found to produce volatile components on ‘Hiratake’ after inoculation. These components were different from the above toxins, and induced rot to the fruit body of ‘Hiratake’. As it is considered that they are one of the pathogenic factors of P. tolaasii, the volatile components were named tentatively as “tovsin” in this report. Tovsin caused browning and rotting to mushrooms, and inhibited germination of plants' seeds and growth of phytopathogenic fungi such as Rosellinia necatrix, but showed little growth inhibition to bacteria. The intensity of tovsin activity was determined based on its degree of inhibition to the germination of lettuce seeds within one or two days. Quantity of tovsin produced by P. tolaasii depends on the mushroom species and media: a large quantity is produced on ‘Hiratake’ but a little on ‘Enokitake’, and also more can be produced on King's medium B but little on PDA medium. Production of tovsin was inhibited by addition of glucose. Tovsin could be trapped at 0 and -20°C, was basic, with stimulating smell, stable at 100°C, and induced or produced many crystals in King's medium B. These results suggest that tovsin promote the disease of ‘Hiratake’ in cultivating rooms and in packs after harvest.
