Different susceptibility of European grapevine cultivars for downy mildew

Downy mildew, caused by the obligately biotrophic peronosporomycete Plasmopara viticola, is one of the most destructive of grapevine diseases that occurs worldwide. The classical cultivars of Vitis vinifera, up to date utmost important for wine and table grape production, are all susceptible to P. viticola, resulting in severe epidemics under warm and humid conditions. The aim of our present study was to characterize the susceptibility to infection by P. viticola among different grapevine cultivars grown in European vineyards in comparison to resistant Vitis species. For this purpose we inoculated leaf discs, leaves and whole plants of eight V. vinifera cultivars considered to be susceptible ('Albariño' [Clone1, Clone2 and Clone3], 'Tempranillo', 'Touriga Nacional', 'Riesling', 'Pinot Noir', 'Pinot Blanc', 'Müller-Thurgau' and 'Cabernet Sauvignon') with P. viticola under controlled conditions. Four Vitis genotypes with a distinct degree of resistance to P. viticola (V. riparia, V. rupestris, V. amurensis and the hybrid Vitis x vinifera 'Solaris') were used as resistant and partially resistant references. To assess the degree of susceptibility we scored the disease incidence and severity visually and microscopically analyzed the course of host tissue colonization by the pathogen. The microscopical studies indicated even slight differences in the infection rate, the course of host tissue colonization and the parasitation i.e. haustoria formation, among the V. vinifera cultivars. The obtained data were suitable for statistical analysis that showed significant differences in the assessed parameters among the V. vinifera cultivars. The principal component analysis (PCA) of the data revealed three groups of susceptibility:genotypes which are little susceptible, e.g. 'Cabernet Sauvignon', 'Pinot Blanc', 'Pinot Noir', 'Müller-Thurgau' and 'Riesling';a second group formed by those genotypes which are very susceptible, i.e. the two clones of 'Albariño' (the most susceptible of all) and 'Tempranillo'; anda third group comprising the genotypes used as resistant and partially resistant references (V. riparia, V. rupestris, V. amurensis and the hybrid Vitis x vinifera 'Solaris').Within the first group 'Cabernet Sauvignon' formed a subgroup indicating a very low susceptibility to P. viticola. In this work, for the first time the visual assessment of disease incidence and severity with a microscopical analysis of infection intensity, colonization of host tissue and parasitation to discriminate differences in susceptibility of European V. vinifera cultivars for P. viticola was combined.

Water regime and its possible impact on expression of Esca symptoms in Vitis vinifera: growth characters and symptoms in the greenhouse after artificial infection with Phaeomoniella chlamydospora

Impact of abiotic factors has been recently discussed in grapevine trunk diseases such as Esca. Emphasis of the present study lies on the relation between different water regime ("normal" and "stress") on one side and growth characters as well as Esca-related wood symptoms on the other side. Trials were conducted in the greenhouse with cuttings of the cultivars 'Müller-Thurgau' and 'Riesling', part of which artificially infected with Phaeomoniella chlamydospora. During a 12 month incubation period the following characters were evaluated: shoot length, weight of stem, expression of wood symptoms, and survival rate of plants. For evaluation of wood symptoms a numerical system was developed that is applied here for the first time. The obtained results indicate that water supply plays a statistically significant role, with plants under "stress" regime shown to be more affected. No strict spatial correlation was found to exist between wood symptoms and physical presence of the pathogen

Erratum

The influence of temperature during the development of conidia on the germination of Uncinula necatorVitis 34(1), 63-64 (1995

Elimination of grapevine leafroll associated virus type I in Vitis vinifera cv. Lemberger

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Fungi associated with Esca disease of grapevine in Germany

Esca disease of grapevine is gaining increasing importance in Central European wine-growing countries. Several fungi, all of which are wood-inhabiting, were found to be associated with the disease. The taxa thought to act as main causal agents are the basidiomycete, Fomitiporia mediterranea, and, less frequently, the deuteromycetes, Phaeomoniella chlamydospora and Phaeoacremonium aleophilum. In addition, the species Eutypa lata, Phomopsis viticola, Botryosphaeria obtusa, and Cylindrocarpon destructans were isolated from Esca-affected vines. These species have been described in a standardized style and information is provided on taxonomy, cultured mycelium, microscopical characters, nuclear behaviour, as well as restriction and sequence data of ribosomal DNA

Resistance to transmission of grapevine fanleaf virus by Xiphinema index in some Vitis species and hybrids

Many vineyards in Germany are infested by nematodes which can transmit virus diseases. Breeding of rootstocks resistant to nematode feeding and virus transmission is an important way to control these virus diseases. A method has been developed for testing breeding stocks for these characteristics with regard to grapevine fanleaf virus (GFV) and its vector Xiphinema index. The plants to be tested were first grown together in a single pot with both GFV-infected plants of Vitis cv. Siegfried and plants of the same cultivar which were virus negative according to an ELISA test: 2 months after planting, the pots were inoculated with about 50 nematodes. In a second experiment, single healthy plants of different hybrids and species were potted and inoculated with about 200 nematodes carrying GFV. After 3-10 months, roots were inspected visually for swellings and galls and tested for the presence of GFV by ELISA. In all cases, the previously healthy cv. Siegfried showed symptoms of feeding on the roots and these roots showed a positive reaction to the ELISA test. After 6 months, GFV could also be detected by ELISA in the basal parts of the stems. The reaction of the test plants was dependent on their genotype. A high susceptibility to feeding by the nematodes and high percentage of transmission to GFV was displayed by American species and interspecific hybrid rootstocks. One of the V. vinifera x V. rotundifolia hybrids showed no visual symptoms of nematode feeding and no virus transmission 9 months after inoculation

Evaluation of downy mildew resistance in various accessions of wild Vitis species

107 accessions of 21 species from America and East Asia were investigated for resistance to downy mildew, Plasmopara viticola, by the leaf disc test. The species, Vitis rotundifolia, munsoniana and yenshanensis showed resistance in all accessions investigated (rating 1.0). Vitis cinerea, palmata and shuttleworthii can be rated as moderate resistant (rating 1.1 - 1.9). In V. candicans, doaniana, piasezkii, riparia, rubra and tiliifolia resistant as well as susceptible accessions were observed. In V. acerifolia, aestivalis, amurensis, champinii lanata, rupestris, solonis, vinifera and vulpina all accessions showed susceptibility to the fungus, the rating varied from 1.1 to 7.2

Isolation of Agrobacterium vitis from grapevine propagating material by means of PCR after immunocapture cultivation

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