METHOD FOR CONTROLLING BACTERIAL BLOTCH DISEASE IN EDIBLE MUSHROOMS

Abstract: The present invention relates to a method for controlling bacterial blotch disease in edible mushrooms, comprising of treating the mushrooms with one or more lipodepsipeptides. The lipodepsipeptides are for instance chosen from WLIP and viscosin. The invention further relates to the edible mushrooms treated in this manner and a solution which can be used in the treatment.

Description: METHOD FOR CONTROLLING BACTERIAL BLOTCH DISEASE IN EDIBLE MUSHROOMS The present invention relates to a method for controlling bacterial blotch disease in edible mushrooms, to the result of the method and to products for use in the method. Edible mushrooms are products about which most consumers have a definite opinion. In particular, mushrooms must have a white colour and be unblemished. Infection with Pseudomonas tolaasii results in pits and brown blotches which affect the appearance of particularly white mushrooms, such as the button mushroom. This results in an average of 10-15% of the harvest being rejected, being given a lower classification or having to be processed into preserves. Pseudomonas tolaasii is actually always present in the compost on which mushrooms are cultivated. The problem of the formation of blotches and pits on the mushrooms occurs when the quantity of bacteria exceeds a determined threshold value. At present diluted bleach is atomized over the culture bed. However, bleach is harmful to the environment, consumer-unfriendly and difficult to dose. The use thereof should therefore preferably be avoided. It is therefore the object of the present invention to provide a method with which bacterial blotch disease in edible mushrooms can be controlled. This objective is achieved with the invention by means of a method comprising of treating the mushrooms with one or more lipodepsipeptides with a β-structure. Lipodepsipeptides are molecules which partially consist of a peptide structure, contain a lipid part and have a lactone ring. One of the best known lipodepsipeptides is the so-called "White Line Inducing Principle" or WLIP. This is a substance which is found in the white line which results when saprophytic Pseudomonas species, which are jointly designated as P. reactans, are grown in agar together with Pseudomonas tolaasii, the cause of blotch disease. The structure of WLIP is shown in Figure 1. The official name of WLIP is β-hydroxydecanoyl-LLeu-DGlu-D, allo-Thr-DVal-DLeu-DSer- LLeu-DSer-LIle. In addition to WLIP, another lipodepsipeptide occurs which bears the name viscosin and only differs from WLIP in the chirality of Leu5, which in the case of viscosin has the L-configuration and in the case of WLIP the D-configuration. Viscosin is produced by Pseudomonas viscosa. In addition to WLIP and viscosin, other lipodepsipeptides can also be used according to the invention, provided they have a β-structure. According to the invention crude preparations of the lipodepsipeptides and purified forms thereof can be used to treat bacterial blotch disease. The method according to the invention is in principle suitable for all edible mushrooms which have bacterial blotch disease. Because the lipodepsipeptides have a white colour they can therefore be used as such for the treatment of white mushrooms, such as Aσaricus bisporus (button mushroom) , Aσaricus arvensis (horse mushroom) , Aσaricus bitorquis (torq) , and Flamulina velutipes and Pleurotus spec, (white oyster mushroom) . For treatment of differently coloured mushrooms such as shiitake, a diluted solution is preferably used or a dye is added to the lipodepsipeptide preparation, since white blotches would otherwise result from the treatment . The treatment of the mushrooms can take place at different moments in time and in different ways. A solution of one or more of the lipodepsipeptides can be atomized or sprayed over the culture bed. The culture bed can further be watered with a solution containing the compound (s). These treatments take place before harvesting. It is however also possible to treat bacterial blotch disease after harvesting. It is then of course important that no damage has yet been caused and the mushrooms are still unblemished and undamaged. The treatment after harvesting can for instance consist of atomizing or spraying with a solution containing one or more lipodepsipeptides. The compound (s) can be administered in a concentration between 1 mg/1 and 1 g/1, preferably 0.1 g/1. 10 ml of the compound is for instance administered per kilogram of mushrooms. The invention further relates to edible mushrooms which are the result of a method according to the invention. In addition, the invention relates to a preparation of one or more lipodepsipeptides for the treatment of bacterial blotch disease in edible mushrooms. The present invention will be further elucidated with reference to the following examples, which are only intended by way of illustration and do not limit the invention in any way. EXAMPLES EXAMPLE 1 Inhibition of brown staining by WLIP at different concentrations of P. tolaasii A WLIP preparation was prepared by centrifuging off an overnight culture of Pseudomonas reactans cultured in a medium suitable for this purpose. The supernatant was stored in frozen state. After defrosting the supernatant was filtered and acidified. The resulting precipitate was collected and resuspended in water. The pH of the solution was made slightly alkaline and the preparation was filtered. The filtrate was then acidified again. The resulting precipitate was collected and dried. This is referred to as "crude extract of WLIP". Caps of the button mushroom (A.bisporus ϋl) were treated with water (dark bars) or with the crude extract of WLIP (light bars) in a concentration of 6.6 mg/ml. The caps were subsequently infected with different concentrations of Pseudomonas tolaasii. The brown staining was measured with a Minolta colorimeter and detected after 2 days incubation at 18°C. The degree of brown staining was calculated by deriving AE from the changes in the L-, a- and b-parameters in accordance with the formula: AE = j ( AL ) 2 + ( Aa ) 2 + ( Ab) 2 . The results are shown in Fig. 2, EXAMPLE 2 Inhibition of brown staining by different concentrations of WLIP Caps of the button mushroom (A.bisporus Ul) were treated with different concentrations of a crude extract of WLIP. The caps were subsequently infected with Pseudomonas tolaasii in a concentration of 5.5 x 10 7 cells per ml (dark bars) or 1.3 x 10 7 (light bars) and the brown staining was detected after 2 days incubation at 18°C. The results are shown in Fig. 3. EXAMPLE 3 Inhibition of brown staining by WLIP in time Caps of the button mushroom (A.bisporus Ul) were treated with water (full line) or a crude extract of WLIP in a concentration of 6.6 mg/ml (dotted line). The caps were subsequently infected with 4.6 x 10 7 (Fig. 4a) or 1.3 x 10 7 (Fig. 4b) of Pseudomonas tolaasii, incubated at 18° and the brown staining was monitored for 4 days. EXAMPLE 4 Inhibition of brown staining by WLIP at different temperatures Caps of the button mushroom (A.bisporus Ul) were treated with water (dark bars) or a crude extract of WLIP in a concentration of 2.4 mg/ml (light bars). The caps were subsequently infected with different concentrations of Pseudomonas tolaasii. Incubation took place for 2 days at 4°C (Fig. 5b) or 18°C (Fig. 5a) . The brown staining was then determined. EXAMPLE 5 Inhibition of brown staining by different concentrations of WLIP Caps of the button mushroom (A.bisporus Ul) were treated with different concentrations of pure WLIP. Pure WLIP was prepared from the preparation described in example 1. For this purpose this preparation was dispersed in an alcohol, dried, dispersed once again in this alcohol and the precipitate was collected and dried. The WLIP preparation was dispersed in water and stored in frozen state. The caps were subsequently infected with Pseudomonas tolaasii in a concentration of 7.6 x 10 6 cells per ml and the brown staining was detected after 2 days incubation at 18°C. The results are shown in Fig. 6. It has been found that in all cases the brown staining of the caps treated with WLIP is significantly lower than of the caps treated with water. •*•****

Claims: CLAIMS 1. Method for controlling bacterial blotch disease in edible mushrooms, comprising of treating the mushrooms with one or more lipodepsipeptides. 2. Method as claimed in claim 1, characterized in that the lipodepsipeptides are chosen from WLIP and viscosin. 3. Method as claimed in claim 1 or 2, characterized in that the treatment takes place by atomizing a solution of the lipodepsipeptide (s) over the mushrooms. 4. Method as claimed in claim 1 or 2, characterized in that the treatment takes place by spraying the mushrooms with a solution of the lipodepsipeptide (s) . 5. Method as claimed in claim 1 or 2, characterized in that the treatment takes place by administering the lipodepsipeptide (s) via the watering of the mushrooms. 6. Method as claimed in claims 1-5, characterized in that the treatment takes place before harvesting of the mushrooms . 7. Method as claimed in claims 1-4, characterized in that the treatment takes place after harvesting of the mushrooms . 8. Method as claimed in claims 1-7, characterized in that the lipodepsipeptide (s) is/are administered in a concentration between 1 mg/1 and 1 g/1. 9. Method as claimed in claim 8, characterized in that about 10 ml of a solution of the lipodepsipeptide (s) is administered per kilogram of mushrooms . 10. Method as claimed in claims 1-9, characterized in that the mushrooms are chosen from the species Aσaricus bisporus, Agaricus arvensis, Agaricus bitorquis, Flamulina velutipes, Pleurotus spec. 11. Method as claimed in claims 1-9, characterized in that a dye is added to the lipodepsipeptide (s) and the mushrooms are chosen from non-white species such as shiitake. 12. Edible mushroom which is the result of a method as claimed in claims 1 to 11. 13. Solution of one or more lipodepsipeptides for use in controlling bacterial blotch disease in edible mushrooms .

Inventors: SOLER RIVAS CRISTINA, WICHERS HARM JACOB, SOLER RIVAS, CRISTINA, WICHERS, HARM, JACOB
Applicants: INST VOOR AGROTECH ONDERZOEK, SOLER RIVAS CRISTINA, WICHERS HARM JACOB, INSTITUUT VOOR AGROTECHNOLOGISCH ONDERZOEK (ATO-DLO), SOLER RIVAS, CRISTINA, WICHERS, HARM, JACOB
Application year: 1999
Main classification: A01N43
IPC codes: A01N43, A01N63