Master the manuring methods of edible fungi, several common orchid viruses and their transmission routes

1. Common orchid virus

1. Cymbidium mosaic virus

CymbidiumMosaicVirus referred to as CyMV (1) Orchid plants infected by Cymbidium mosaic virus often have a tendency to produce gangrene, such as black gangrene freckles, gangrene stripes and so on. In addition to gangrene in the leaves and stems of susceptible plants, gangrene also occurs in flowers, which is a unique disease of Cymbidium mosaic virus. The susceptible orchid varieties are Orchid, Cardelia orchid, Oncidium, Tiger Orchid, Wandai Orchid and Phalaenopsis. Gangrenous spots sometimes occur only on the lower appearance of the leaves but not on the upper appearance, which occurs on Oncidium, Dendrobium, Wandai Orchid and Phalaenopsis, so it is often mistaken for fungal infection by growers. Some Cymbidium plants infected with Cymbidium mosaic virus, such as Cymbidium, Cymbidium, Oncidium and Phalaenopsis also produce yellow-green mottled mosaic or yellow stripe disease. In addition, some orchid varieties do not show any distinguishable symptoms after infection.

(2) virus characteristics and transmission methods Cymbidium mosaic virus is a kind of potato virus X (potexvirus). Although the extracellular firmness of this virus is not as strong as that of tobacco mosaic virus, it is also a very strong genus of known viruses. The granules can be zigzagged slightly, the length is about 450nm, the extracellular heat resistance temperature is 60 ℃ to 70 ℃, and can survive for 25 days at room temperature.

At present, no vector insect capable of transmitting Cymbidium mosaic virus has been found, and its transmission route is exactly the same as that of Dichondra ringspot virus, which is invaded and infected by root mechanical wounds.

two. Toothed glossy ringspot virus

OdontoglossumRingSpotVirus

According to the report of ORSV (1) disease, more than 20 genera of orchids can be infected with orchid ringspot virus. The diseases caused by different orchids or orchids will be different. Orchids such as Phalaenopsis, Oncidium, Cartland, Orchid, Magnolia and Cymbidium are often easily infected by orchid ringspot virus, especially Phalaenopsis. The earliest disease recorded in the literature is ringspot, and mosaic, streak, yellow stripe, color streak, and even gangrene have been recorded. Mosaics and stripes are the most common among these diseases. In addition, some orchid varieties do not show symptoms after being infected with orchid ringspot virus, which is particularly common in the seedling stage of Phalaenopsis and Oncidium. Infected plants usually wait until the first flowering before gradually emerging symptoms. In addition, it is very common for Cymbidium mosaic virus and glossy orchid ringspot virus to co-infect the same orchid plant in artificial orchid orchid garden, and the disease will be much more serious than that of single virus infection.

(2) characteristics and methods of transmission of the virus Dentoglossa ringspot virus is a kind of tobacco mosaic virus (Tobamovirus). The granule is in the shape of a short hard rod with a length of about 300 nm. The common characteristic of this virus is that it is extremely stable, has strong extracellular heat tolerance in the host, and can survive for quite a long time at a temperature as high as 95 ℃. According to the report of Japanese scholars, the orchid ringspot virus can survive outside the cell for more than 10 years under 20 ℃. It is a highly consolidated infectious virus. The virus can only invade plants through mechanical wounds, so in the process of tissue culture or greenhouse cultivation and management, all operations that may cause superficial wounds, including flower stalks, pruning, and even friction between plant leaves, may become the way for the virus to invade and infect. So far, it has not been confirmed that toothed glossy ringspot virus can be transmitted by any unique vector insects. However, any insect or small animal that may cause mechanical damage on the orchid plant, such as cockroaches and snails, will increase the possibility of glossy ringspot virus infection and should be on guard.

three. Cucumber mosaic virus

CucumberMosaicVirus abbreviated as CMV (1) the earliest record of cucumber mosaic virus infecting orchids was found in Phalaenopsis. The disease recorded at that time was the emergence of yellowing stripes parallel to the veins on the leaves of the plant. Cucumber mosaic virus can also cause discoloration or stripes in the petals of safflower strain Phalaenopsis. In addition, cucumber mosaic virus infection has been found in Oncidium specimens. The leaf of the specimen showed an unobvious spot disease, and yellow stripes parallel to the leaf vein could be seen vaguely, but the plant size was no different from that of the normal plant.

(2) virus characteristics and transmission methods Cucumis mosaic virus is a kind of Cucumovirus. The granules are spherical ones with a diameter of 28 nm. The host field of this virus is very extensive, and it can infect more than 800 species of plants belonging to 365 genera and 85 families. Cucumber mosaic virus infection has been recorded in most important cash crops in many areas of China, and its population is very common in the field. The virus can be transmitted from wounds caused by mechanical friction. In the field, aphids are mainly transmitted by aphids by non-sustainable methods, because there are many species of aphids that can transmit cucumber mosaic virus, so the virus is widely spread.

The best way to prevent and cure orchid virus disease is to prevent its introduction before the disease occurs, that is, to thoroughly understand the possible transmission path and origin of the virus, and then to ban it completely, so as to eliminate the opportunity of virus introduction.

one. The way to get infected with the virus in the process of orchid production.

(1) if the infected plants are used as parents for pollination, the pods are used for aseptic sowing to breed seedlings, and the infected pods and villi contain high concentrations of virus, which will contaminate the seeds and medium in the sowing process. Because glossy orchid ring spot virus and cymbidium mosaic virus are extremely solid viruses, they can survive outside the cell for a long time. After the orchid seeds germinated, the virus infected some of the seedlings due to the wound invasion caused by the human transplant operation. These seedlings become the source of virus infection, continue to pollute the rest of the plants in the subculture, and even become the source of virus pollution and infect the rest of orchid seedlings in the process of seedling maturation and colonization.

(2) because the varieties of the plants that have been infected with the virus meet the market demand, the operators carry out meristem culture without virus test, and a large number of cloned seedlings are breed, resulting in all the seedlings carrying the virus.

(3) although the operators screened the parents with high quality traits for virus detection, these parents were in the period of infection, so the virus concentration in the tissue was low or distributed unevenly, and the test results mistakenly believed that these parents had no virus infection. These parents were used to clone the meristem, resulting in the seedlings carrying the virus.

(4) the parents with high quality traits were not infected with the virus, but were contaminated by the virus in the process of tissue culture. If the meristematic seedlings are contaminated by the virus during the mother bottle period, all the subsequent seedlings will carry the virus. According to the survey, the processes and skills used in the operation process can not completely avoid virus pollution, which may lead to mutual transmission between different batches of orchid seedlings.

two. A method of operation that may cause virus transmission.

(1) inaccurate tool disinfection methods: the operating tools used in tissue culture, such as tweezers and scalpels, must go through sterilization procedures to avoid bacterial and fungal infection, so operators can adopt different sterilization methods according to their own habits. Traditionally, high temperature sterilization is adopted, such as dry heat sterilization in high temperature oven, wet heat sterilization in high pressure sterilizer and flame sterilization in aseptic operating table.

Because the nature of orchid ringspot virus and cymbidium mosaic virus is extremely strong, in the absence of appropriate and effective eradication methods, the virus is very likely to retain the table or tools that contaminate the aseptic console for a long time. It even contaminates the hands and clothing of operators, thus having a chance to indirectly infect tissue culture seedlings.

(2) the petri dish is contaminated: in addition to using the aseptic console for the transfer of tissue culture seedlings, the staff will also use petri dishes or supports to isolate the direct contact between the tissue culture seedlings and the aseptic console during the operation. However, if it is not used properly, it will cause pollution between different batches of seedlings. Solemnly speaking, petri dishes must be changed with different batches of seedlings. Because if the previous batch of seedlings is infected with the virus, it may contaminate the appearance of the petri dish, and the re-use of the contaminated petri dish will cause the next batch of seedlings to be infected with the virus.

(3) neglect and bad habits of staff: neglect or bad habits of staff in the process of operation may increase the probability of tissue culture seedlings infected with the virus. For example, carelessness and incompleteness in the use of flame disinfection tools, or failure to change petri dishes in time are the key factors that tissue culture seedlings are difficult to avoid virus infection.

Managers can take measures such as training employees, cultivating their professionalism and strengthening character monitoring to reduce the probability of virus infection of seedlings.

three. The tissue culture seedlings were not infected with the virus, but were infected by the virus in the process of colonization out of the bottle.

According to the investigation, even if the meristem seedlings do not have virus infection in the bottle, if dignified measures are not taken to prevent virus infection in the process of cultivation, virus infection will still occur.

These common mistakes include: (1) after the operator removes the seedling from the bottle, wash the residual medium in the container or solve it with protective medicine. if the seedlings of different batches are solved with the same container, and some batches of seedlings carry the virus, the residual virus will contaminate the appearance of the container, resulting in virus infection in the next batch of seedlings.

If some individuals in the same batch of seedlings are infected with the virus, when all the seedlings are solved in the same container, the rest of the individuals will also be infected.

(2) the workbench, tools or hands of the staff used in the seedling colonization operation may come into contact with the virus-carrying seedlings and be infected with the virus in the process of transplantation, thus becoming the vector for the transmission of the virus.