Grapevine Biotechnology
Virus elimination from vines
Viral diseases reduce the performance of the vines. The consequences are loss of yield stability and low quality. It is not possible to recover the vine through plant protection measures, so that the removal of the vine, and possibly even the uprooting of the entire vineyard, becomes necessary.
The most relevant viral diseases for German wine-growing regions are transmitted by nematodes living in the soil. The most important viral disease is grapevine fanleaf degeneration, caused by the grapevine fanleaf virus (GFLV) or other nematode-borne viruses. Since chemical decontamination of the soil was banned since the 1990s as a sanitary measure to eliminate the virus carriers, viral diseases can already be observed in young plants. In these cases, the economic damage is considerable. Although fanleaf degeneration is the most common, it is not the only virus that causes damage in German wine-growing regions.
Leafroll disease is caused in German wine-growing regions by types 1 and 3 of the grapevine leafroll-associated virus (GLRaV). Leafroll disease is the most widespread grapevine virosis worldwide. Various species of scale insects and mealybugs are considered potential vectors in the vineyard. However, both diseases can be transmitted during vine grafting. As there are no direct control measures against these viral diseases and there are no natural sources of resistance, the only option is to carefully monitor the propagation stock and use only healthy planting material. The situation is also problematic if rare clones or varieties are only available as virus-infected material (variety collections). Since virus-infected vines may not be placed on the market, the only way out is to eliminate the virus.
Chemotherapy, thermotherapy and somatic embryogenesis and regeneration. In the case of chemotherapy and thermotherapy, in vitro cultures of shoot tips are created and treated with either antiviral agents or a specific temperature and exposure regime. Depending on the type of virus present, rapid growth and repeated transfer of the shoot tips can lead to their elimination from the tissue. For some viruses, however, these methods are not sufficient, so that the more complex method of producing somatic embryogenic cell cultures must be used. This dedifferentiation process and the regeneration of whole plants can completely eliminate the viral infection.
In the case of vegetatively propagated cultivated plants, the production of virus-free clones, which serve as the basis for maintenance breeding, is one of the most important measures in combating the virus. In principle, various methods are available for this purpose:
Chemotherapy, thermotherapy and somatic embryogenesis and regeneration. In the case of chemotherapy and thermotherapy, in vitro cultures of shoot tips are created and treated with either antiviral agents or a specific temperature and exposure regime. Depending on the type of virus present, rapid growth and repeated transfer of the shoot tips can lead to their elimination from the tissue. For some viruses, however, these methods are not sufficient, so that the more complex method of producing somatic embryogenic cell cultures must be used. This dedifferentiation process and the regeneration of whole plants can completely eliminate the viral infection.