Infection cycle of viral diseases

Viruses are parasites in living cells. It does not have the ability to destroy the plant cell wall, nor can it carry out saprophytic life on the dead cell tissue as a parasitic transition like other parasites with saprophytic ability. Therefore, when the virus invades Lan Mei, a slight wound must be required. This kind of wound can not only cause damage to the cell wall, but also not lead to a large number of cell death. In this way, the virus can immediately come into direct contact with living cells and further proliferate and expand in the cells. During orchid cultivation, such minor wounds may come from abrasions on healthy and diseased plants when they come into contact with each other, or stab wounds or artificial pruning and mechanical injuries of insects, especially insects with piercing mouthparts. After entering the living cell, the virus can only expand passively by relying on the transport mechanism of the host. When it is in parenchyma, it slowly expands from one cell to another. But once it reaches the phloem, it begins to move rapidly with the liquid flow of the plant.

It is estimated that the incubation period of infection and parasitism of Jian Cymbidium mosaic virus is about 30 days in summer and 20 days in winter of 15 degrees, and the in vitro survival time is 60 ~ several days. The lethal temperature is 60-80 degrees; the incubation period of infection and parasitism of orchid ringspot virus is about one week, the in vitro survival time is more than 763 days, and the lethal temperature is more than 93 degrees.

It has not been reported that the main drivers of fungal and bacterial transmission-air currents, currents, and Rain Water-play an role in the spread of the virus. Most of them rely on insects as vectors. Occasionally, it can be spread by contact and friction of diseased plants.

The insects that transmit the virus are mainly species with piercing and sucking mouthparts, among which aphids and leafhoppers are particularly important. And scale insects are also questionable. Some people think that nematodes can also spread orchid virus. The virus can maintain its vitality in the insect for a long time. As long as the insect feeds on the susceptible plant, it can spread the virus for a long time, even for a lifetime. The virus can proliferate continuously in the strange body of insects, and even pass on to its offspring with the reproduction of insects.

The virus mainly exists in the salivary glands of insects and infects the orchid strain when the insect enters the plant with saliva.

In the process of cultivation, because of ramet, pruning roots and leaves, making pruning tools carry virus and spreading each other is also the main way of orchid virus disease. There is no doubt that the main sources of viral diseases are living parasitic plants and insects. Once the orchid strain is infected with the virus, the virus will survive in the plant for a long time, unless Lanlin dies or is artificially destroyed. (Liu Zhongjian)