More about in vitro grape virus symptomatology

Abstract

An in vitro grafting method adapting the usual “indexing by green grafting” technique (Walter et al., 1990) to in vitro culture conditions was tested. The local grapevine varieties Khamri Tozeur, Akhel Meguergueb, Jerbi Degueche, Asli and Jebbi, infected respectively with infectious degeneration, leafroll, vein mosaic, corky bark and vein necrosis diseases, were used. Virus expression was greater on media having a greater number of nutrients such as the Van Hoof (1974) medium containing 12 macronutrients. On the other hand, the addition of BAP (0.25 mg l-1) to the medium reduced external virus symptoms on newly sprouted axillary shoots. When these shoots were transferred to fresh culture medium supplemented with IBA (0.1 mg l-1), typical and specific symptoms of major virus diseases clearly developed. Re-grafting of axillary shoots on the fragment of an infested clone can be used to overcome difficulties related to corky bark and vein mosaic symptom expression. We also demonstrated that viruses occur in general in mixed infections. The symptoms of a given virus become evident only when favourable conditions to it arise. Our research is still working on reducing the time of detecting virus and virus-like diseases. This is essential for sanitary selection of grapevine plants.