Inducible silica incrusts in cell walls of Vitis leaves

Epidermal cells of Vitis cvs attacked by powdery mildew or damaged mechanically exhibited silica deposits in the walls of the attacked and surrounding cells. Entire or parts of cell walls were vitrified to such an extent that pure, mechanically resistant silica skeletons remained after a treatment with conc. H2S04 + H2O2 at 400 °C and washing with conc. HCl. They consisted of groups of 1-20 cells of the upper epidermis with adhering parts of the corresponding palisade cells or of the lower epidermis (including stomatal cells) with adhering spongy parenchyma. Not only cell walls but also wrinkles of the upper epidermis, defense papillae and fungal haustoria were silicified. Silica accumulations were greater in resistant than in susceptible cultivars

Isoelectric focusing of grapevine peroxidases as a tool for ampelography

Enzymatically active proteins have been isolated from the phloem of internodes of 71 Vitis species and cultivars and separated by thin layer electrofocusing. Peroxidases (EC 1.11.1.7.) yielded a pattern which could be differentiated into up to 8 bands within the pH range 6 through 11. The patterns obtained from different samples were congruent with ampelographic data, they are virtually identical within the families of Pinot and Silvaner, as weil as between haploid and diploid forms of one variety, even under different environmental conditions. American and Asian wild species and some interspecific hybrids show a slight shift of the isoelectric point of one enzyme band as compared to Vitis vinifera varieties

Uptake of silica by grapevines from soil and recirculating nutrient solutions

The uptake of silica by grapevines was investigated both in the field and in hydroponic cultures. In aqueous soil suspensions (14 d at 20 °C) of 6 different locations (clay/loam) an equilibrium of 55-71 ppm of soluble silica (expressed as SiO2) was measured; the content of grapevine leaves at harvest time was between 0.44 and 0.73 % of the dry matter, the concentrations being correlated with the silica solubility of the relative soil. Before budburst xylem exudates contained only about 1-4 ppm SiO2 (rising with soil temperature), whereas during summer up to 68 ppm were measured. Six different grapevine cultivars were grown in recirculating nutrient solutions supplied with different amounts (112, 10 and 0 ppm) of SiO2; the solutions were changed weekly. The average SiO2 content of leaf dry matter at harvest time (0.1-2 %) was correlated with leaf age and the SiO2 concentration of the nutrient solution whereas in stems and petioles it was always less than 0.1 %. Significant varietal differences could be found only for cv. Regent which accumulated about 20 % more SiO2 than the other varieties from the 112 ppm solutions. By the end of the vegetation period fresh leaves from plants grown on 112 ppm contained always around 0.1 % of water soluble SiO2, irrespective of the leaves' age whereas the total amount of SiO2 was up to 2 % in old leaves from the basis of the shoots and less than 0.5 % in the apical region. In the leaf center the silica concentration was always around 50 % lower than in the leaf periphery

Metabolism of stilbene phytoalexins in grapevines: Oxidation of resveratrol in single-cell cultures

Single-cell cultures of the fungus resistant grapevine varieties Pollux and Sirius and the susceptible ones Riesling and Optima have been established to study the metabolism of the stilbene phytoalexins resveratrol and viniferin. Cells of different varieties showed morphological differences (form and mechanical resistance) and their susceptibility to treatment with debris of killed mycelium of Bot1ytis cinerea reflected the varietal resistance under natural conditions. Most cells of Riesling and Optima were killed by toxic components of the mycelium within 60 h, whereas cultures of Pollux and Sirius showed only slight damage. Two types of peroxidases have been characterized which can take resveratrol as a substrate converting it to a brown pigment. Viniferin was observed as an intermediate product. Peroxidase activity in suscpetible varieties was reduced as compared to the resistant ones. The oxidation products of resveratrol inhibited the activity of peroxidase. The function of stilbene phytoalexins as precursors of lignin-like substances is discussed

Structural characters of epidermal cell walls and resistance to powdery mildew of different grapevine cultivars

The analysis of 12 grapevine cultivars differing in susceptibility to powdery mildew revealed a correlation between the thickness of cuticle plus cell wall of young leaves and resistance to mildew. Neither in mature leaves or in leaves of in vitro plants or in berries such correlations could be established. Coating of the leaf surface with a polymetacrylate antitranspirant prevented sporulation in all cases, although infection structures were formed

The influence of silica fertilization on the resistance of grapevines to powdery mildew

Six different Vitis cultivars grown in recirculating nutrient solutions supplied with 0, 10 and 112 mg.l-1 SiO2, respectively, were infected with spores of the powdery mildew fungus Uncinula necator and analyzed after 2, 4 and 6 weeks. Whereas the size of the silica endoskeletons induced by the powdery mildew was influenced by the SiO2 concentration, the cultivar-specific resistance could not be increased. However, after 2 weeks all varieties showed a slightly but significantly enhanced resistance in the 112 mg.l-1 solution which disappeared during the following weeks. The results show silica to be essential for a normal powdery mildew resistance but make evident that the Oidium susceptibility of cultivars cannot be overcome by supplementary silica fertilization in the field, the Si contents of most soil solutions being far above the minimal requirements of the grapevine

Ein preiswertes Bildauswertesystem für die Züchtungsforschung

A low cost image analysis system for breeding researchAn image analysis system is described consisting of an ATARI ST microcomputer equipped with a digitizer and a black and white videocamera which allows the analysis of 400 x 400 dot images by a software program written in PASCAL and assembler language. The program has been developed for the particular needs of breeding research and allows measurements of leaf surfaces and fruit and seed sizes, determination of leaf areas damaged by disease and scanning of chromatograms and isoenzyme patterns. Data may be saved on PC-compatible diskettes and can thus be processed by other systems. The hardware costs less than 3000 DM, the software may be easily adapted to other requirements by anyone familiar with PASCAL programming

Fluorescence kinetics of chloroplasts as indicators of disorders in the photosynthetic system I. Comparative studies with greening leaves of Vitis and Hordeum

Kinetics of both delayed fluorescence (luminescence) and prompt fluorescence of chlorophyll are used to characterize photosynthetic activity in leaf tissues. In a first attempt the greening process in etiolated Vitis cuttings and Hordeum seedlings was studied. Data sampling and processing, including averaging of the kinetics, was carried out by means of a microcomputer. Parallel to the light-induced development of photosynthetic activity the kinetic changes (i. e. luminescence decrease, fluorescence rise and decrease) became more prominent and transitory secondary peaks appeared. For both plants the succession of the kinetic characteristics was the same; it only differed in the time of appearance. The kinetics are discussed according to interpretations given in literature. The method is proposed as a tool to quickly characterize certain damages of the photosynthetic system in different plants

A tripartite aseptic culture system for grape (Vitis spp), phylloxera (Daktulosphaera vitifoliae) and mites (Tarsanemus sp.)

Research Not

Identification of grapevine cultivars by DNA analyses: Ptfalls of random amplified polymorphic DNA techniques using 10mer primers

Research Not