Among the specific means against viral diseases is cross protection. That method consists in inoculating a viral strain producing attenuated symptoms, so as to protect the plants against a subsequent infection by severe strains of the same virus. That strain called protecting strain produces symptoms not very severe and does not affect, or slightly, productivity and the quality of the crops. This particularity has also been observed in viroids.
As all agents in biological control, the protecting strain must satisfy several requirements :
- induce light symptoms compared to those provoked by strains met in the fields
- infect the plant in a systemic way so as to protect all its organs
- present a genetic stability so as to minimize the reversion risks in a more severe form
- not being transmissible by vectors so as to avoid a non-intentional dissemination
- protect the plant towards the various strains present in the field
- be easy to produce, to keep and to inoculate
This method can present certain risks that must be rapidly assessed. In certain cases, the protecting strain can reveal itself as being pathogenic on other plants or show a synergy with other viruses on the crop plant. It can also mutate and become pathogenic.
To know more about methods of diagnosis and identification of pathogenic agents, click here.
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