Prevalence of Viruses Infecting Autochthonous Grapevines in Tunisia

The incidence of virus infections was conducted in the grapevine germplasm collection at the Institut National de la Recherche Agronomique de Tunisie. In this grapevine collection, 162 different autochthonous cultivars were maintained, including numerous spontaneous ecotypes coming from different Tunisian grapevine growing regions. All accessions were sampled and analyzed by DASELISA for the presence of Grapevine leafroll associated viruses 1, 2, 3 (GLRaV-1, -2, -3), Grapevine fanleaf virus (GFLV), Grapevine fleck virus (GFkV) and Arabis mosaic virus (ArMV), using commercial polyclonal antisera. Almost all the major grapevine-infecting viruses assayed, except for ArMV, were detected in the tested cultivars. Conversely, all the wild grapevine accessions were found to be free from the same viruses. Out of 141 cultivars submitted to DAS-ELISA, 40.4% were infected with at least one virus. GLRaV-3 was the prevailing virus (23.4%), followed by GLRaV-1 (19.6%), GFkV (9.2%), GLRaV-2 (4.2%), and GFLV (1.4%). Cultivars collected from northern regions (61.4%) were more infected than their homologues from southern regions (19.7%)

Evaluation of Salt Stress-Induced Changes in Polyamine, Amino Acid, and Phytoalexin Profiles in Mature Fruits of Grapevine Cultivars Grown in Tunisian Oases

Salinity stress has become an increasing threat to viticulture in the Tunisian oasis, and more generally, the characterization of salinity tolerance markers can be of great interest for sustainable grape production. This study investigated some metabolic adaptations in different tissues of the ripe berries of indigenous grapevine cultivars after exposure to salt stress to identify the key traits of salt stress tolerance under oasis conditions. We especially focused on the adaptive responses occurring at the level of amino acids, polyamines, and stilbene phytoalexins in the grape berry skin, pulp, and seeds of six grapevine cultivars differing in phenotypic and ampelographic characteristics. Our data showed that amino acids accumulated strongly in the pulp and skin, while resveratrol, trans-piceid and trans-ε-viniferin, as major phytoalexins, significantly accumulated in the seeds. High salinity was also found to increase both the berry skin and pulp contents of essential amino acids such as threonine, valine, leucine, isoleucine, lysine, methionine, and phenylalanine. The amounts of stilbenes also increased under high salinity in the berry skin of all the studied cultivars. Polyamine homeostasis within the different berry tissues suggested enhanced polyamine biosynthesis rather than polyamine oxidation in response to high salinity. Our principal component analysis revealed a clear discrimination between the cultivars based on their metabolic profiles within the ripe berry tissues under high salinity