Describe the methods of diagnosis and identification of plant viruses, and compare their advantages and disadvantages.

A: The commonly used methods for the diagnosis and identification of plant viruses are bioassay, electron microscopy, autumn green technology and molecular biology technology. These methods can be mutually verified in the diagnosis and identification of plant viruses. When testing or identifying, we can weigh the advantages and disadvantages of each method according to the clear goal and choose different methods.

Bioassay is used to study the symptom types and host range of diseases caused by viruses, and also to determine the transmission mode of viruses. Biometrics needs to grow plants in the greenhouse, which is time-consuming. The symptoms after inoculation are influenced by the host's growth state, temperature, humidity and other factors, as well as the experimenter's technology.

Electron microscope technology can directly observe the shape and size of virus particles with high resolution. However, the electron microscope is a large-scale precision equipment, and the use and maintenance costs are high, so many units do not have the conditions.

Serological technology can use the specific antigen-antibody reaction of plant virus and its antiserum to detect and identify virus or antibody. Serological technology is convenient and fast. However, when preparing antiserum, the titer of antiserum prepared by different viruses is different. Some viruses have poor immunogenicity and it is difficult to prepare antiserum. Some viruses are very low in plants and are difficult to purify. It is necessary to prepare antiserum of virus gene protein by molecular recombination and cloning.

Molecular biology technology is to confirm the existence of virus by detecting virus nucleic acid. This method requires small sample size, high sensitivity, strong specificity, rapidity and relatively simple operation, but at present, reagents and equipment costs are relatively expensive.