Showing papers in "Vitis: Journal of Grapevine Research in 2015"

Flavescence doree in France and Italy - Occurrence of closely related phytoplasma isolates and their near relationships to Palatinate grapevine yellows and an alder yellows phytoplasma

Abstract: Grapevine yellows (GY) are diseases of Vitis vinifera caused by phytoplasmas. On the basis of DNA analysis, it is possible to distinguish different groups and subgroups among grapevine phytoplasmas. Flavescence doree (FD), the most serious problem in European vineyards, is caused by a phytoplasma which belongs to the elm yellows group (EY or 16SrV), Differences between 7 phytoplasma isolates in this group, found until now in French, Italian and German grapevines, and 4 phytoplasmas in the same group, isolated mainly from elm and alder in Europe and America, were investigated. These 11 EY-group isolates plus 3 non-EY phytoplasmas, were compared by PCR-RFLP analyses of two different DNA fragments using 8 restriction enzymes. Two French and two Italian grapevine isolates, classified as FD, appeared to be closely related and were also closer to an Italian alder phytoplasma. One French and one Italian FD isolate always showed the same restriction pattern. On the opposite, the three German grapevine isolates related to alder phytoplasmas in Germany appeared to be closer to the two elm phytoplasmas from America and Europe.

Phenologic and growth responses to early and late season water deficits in Cabernet franc

Abstract: Phenologic and ontogenic responses to seasonal water deficits were investigated in the wine grape variety, Cabernet franc, in a California hillside vineyard. Water deficits were imposed by withholding irrigation water before or after the onset of veraison. In continually irrigated vines, midday leaf water potential (Ψ) declined from - 0.4 MPa to approximately -1.1 MPa between budbreak and veraison despite weekly irrigation at a rate which was 2 x the normal production practice for that commercial vineyard. Hence, water deficits may be a common component of grape production in hillside vineyards of California. When water was withheld until veraison, midday Ψ declined more rapidly and reached - 1.4 MPa at the time water was resupplied. For these vines, water status slowly recovered to the level of the continually irrigated vines. The water status of late deficit vines, (water withheld after veraison), decreased rapidly after veraison, reaching a minimum of - 1.6 MPa at harvest. These differences in vine water status had no effect on the major phenological indicators, i. e„ the timing (on basis of time or accumulation of degree days) of bloom, veraison, and harvest. However, early season deficits shortened the period of shoot elongation and node production, decreased the maximum rate of shoot elongation and node production, and accelerated periderm development on current season shoots. Possible ecological implications of accelerated periderm development are discussed. Shoot length and the number of nodes/shoot was reduced approximately 25 % by the early season water deficits. Radial shoot growth was also inhibited by early deficits but much less than axial shoot growth. Shoot growth had essentially ceased in all vines before late season deficits developed. The characteristic double-sigmoid growth pattern of berries was observed regardless of seasonal water deficits. Most fruit growth occurred during the first growth phase in all treatments. The rate of fruit growth was inhibited by early and late season water deficits. Yield was decreased more by early deficits than by late deficits.

Grapevine shoot growth and stomatal conductance are reduced when part of the root system is dried

Abstract: Split-root plants, where the root system was divided between two containers, were used to study the effect of partial drying of the root system on shoot growth and stomatal conductance of grape cultivars Chardonnay and Shiraz (syn. Syrah). When part of the root system was allowed to dry while the other part was well-watered, shoot growth was significantly reduced. Changes in both shoot growth and stomatal conductance in response to half-drying took place in the absence of any change in shoot water status suggesting the involvement of a non-hydraulic signal in mediating this response. Recovery of both shoot growth rate and stomatal conductance appeared to start before rewatering of the dried half of the root system, and coincided with the time when there was no further decrease of soil water content in the dried container. This appears to be first report of a significant decrease in shoot growth in response to partial drying of the root system of grapevines.

Multivariate data analysis as a discriminating method of the origin of wines

Abstract: A data set of 178 wines from Piedmont (Barbera, Grignolino, Barolo) was evaluated by multivariate data analysis in order to both build the category models and single out anomalous samples. By feature selection (Fisher weights) only 8 variables, out of the 28 chemical and physico-chemical original variables of the data set, were selected on account of their high univariate discriminant ability. Classification methods (KNN, LDA, PCA) and modelling techniques (Bayesian analysis, SIMCA) were applied to the 8-dimension data set; classification ability was about 98 %.

Effects of resveratrol, viniferins and pterostilbene on Plasmopara viticola zoospore mobility and disease development

Abstract: The effects of stilbenes (resveratrol, δ- and e-viniferins, and pterostilbene) on the mobility of zoospores of Plasmopara viticola and on subsequent disease development were studied in vitro . δ-viniferin and pterostilbene are the most toxic stilbenes concerning zoospore mobility (ED 50 : 14.6 and 28.3 μM) and disease development (ED 50 : 14.7 and 12.7 μM). The analysis of stilbenes in leaf cells of resistant (Solaris) and susceptible (Chasselas) grape cultivars artificially inoculated with P. viticola has shown that very high amounts of stilbenic phytoalexins accumulate at the site of infection of the resistant cultivar compared to the susceptible one.

Partial drying of the rootzone of grape. I. Transient changes in shoot growth and gas exchange

Abstract: Split-root plants, where the root system was divided between two containers, were used to study the effect of partial drying of the root system on shoot growth and gas exchange of Shiraz (syn. Syrah) ( Vitis vinifera ), Kober 5 BB ( Vitis berlandieri x Vitis riparia ) and 110 Richter ( Vitis berlandieri x Vitis rupestris ). The initial decrease in both shoot growth rate and gas exchange in response to half-drying coincided with the decrease in soil water content of the dried half of the root system. Recovery of shoot function of half-dried grapevines occurred without rewatering of the dried half of the root system, and commenced when there was no further decrease in soil water content. There was no effect of half-drying on leaf water potential at the times of greatest inhibition of shoot growth rate and stomatal conductance relative to control; this suggests the involvement of a non-hydraulic signal originating from the roots in drying soil. Changes in stomatal conductance in response to half-drying were strongly correlated with shoot growth rate.

Canopy microclimate modification for the cultivar Shiraz II. Effects on must and wine composition

Abstract: The degree of shade in Shiraz grapevine canopies was varied by four treatments and a naturally occurring vigour gradient. A shaded canopy microclimate produced must compositions of reduced sugar content and higher malic acid and K concentrations, and pH. Wines from these musts also showed higher pH, K and reduced proportions of ionised anthocyanins. Correlation studies showed that high must and wine pH and K content were positively correlated with shading in the canopy, and that colour density, total and ionised anthocyanins and phenol concentrations were negatively correlated with shading. An eight-character visual scorecard of grapevine canopies was used to describe the canopies, and the results correlated with must sugar, pH and K, and wine pH, acidity, K, colour density, total and ionised anthocyanins and phenol content. Vines of high vigour produced similar must and wine composition as shaded canopy treatments.

Effects of abscisic acid treatment and night temperatures on anthocyanin composition in pinot noir grapes

Abstract: Potted Pinot noir grapevines were grown under continuous high temperature (30 °C) or low night (15 °C) and high day (30 °C) temperatures after veraison. Half of the total number of clusters of each vine was sprayed with 250 ppm abscisic acid (ABA) at veraison. Anthocyanin accumulation in berry skins grown under high night temperatures was lower than that in berries grown under low night temperatures. HPLC analysis showed that the ratios of delphinidin-3-glucoside, cyanidin-3-glucoside and petunidin-3-glucoside to the total anthocyanin content were greatly reduced under high night temperatures. ABA treatment enhanced anthocyanin accumulation under high night temperatures to almost the same level as under low night temperatures; the ratio of each anthocyanin to the total anthocyanin, however, was not affected by ABA treatment.

Partial drying of the rootzone of grape. II. Changes in the pattern of root development.

Abstract: Split-root plants, where the root system was divided between two containers, were used to study the effect of partial drying of the root system on gas exchange and root growth of 110 Richter ( Vitis berlandieri x Vitis rupestris ). The initial decrease in gas exchange in response to half-drying coincided with the decrease in soil water content of the dried half of the root system. Recovery of gas exchange of half-dried grapevines occurred without any further change in soil water content of the dried half of the root system, and coincided with the point at which there was no further decrease in soil water content. For half-dried plants, there was a relative increase in root development in moist soil layers, both in the ‘wet’ container as a whole or in the lower part of the ‘dry’ container. Recovery of gas exchange of half-dried plants occurred at the time when there were no more roots dried in the ‘dry’ container. We propose that, for half-dried plants, the part of the root system in dry soil can survive because water moves from ‘wet’ roots to ‘dry’ roots.

Genotyping of grapevine and rootstock cultivars using microsatellite markers

Abstract: Sixty-six grapevine and rootstock cultivars from an Austrian germplasm collection were genotyped using the following 10 microsatellite loci: VVS1, VVS2, VVS3, VVS4 (THOMAS and SCOTT 1993), VVS29 (THOMAS, pers. comm.), VVMD5, VVMD7 (BOWERS et al. 1996), VVMD28, VVMD32 and VVMD36 (BOWERS and MEREDITH, pers, comm.). All cultivars except those which are thought to be closely related (e.g. Portugieser blau and Portugieser grun) provided unique allelic profiles. A phenogram based on pairwise similarity values revealed the separation of rootstock cultivars from the Vitis vinifera varieties. The probability for the presence of null alleles was estimated from heterozygote deficiencies and null alleles were statistically excluded at 9 of the 10 loci. In order to demonstrate the distinctive power of the microsatellite markers investigated, gene diversity (GD) values were calculated. For both grapevine and rootstock cultivars we estimated a GD range from 0.70 to 0.91, while GD values for grapevines only range from 0.52 to 0.87 and values for rootstocks from 0.29 to 0.86.

Patterns of water flow in Riesling berries in relation to developmental changes in their xylem morphology

Abstract: Using a water soluable dye as tracer, the pattern of xylem water movement within Riesling berries was found to change soon after the onset of ripening, i. e. 'veraison'. Xylem water flow appears to be both slowed and diverted. Initially it flows predominantly in the berry's peripheral xylem system but later flow is much reduced and the remaining xylem component is exclusively in the progressively less conductive axial system serving the seeds. These changes which must force proportionately more water through the phloem path appear to be brought about by morphological change - the appearance of breaks in the peripheral xylem bundles - coinciding with the period of renewed expansion growth which occurs immediately after the onset of ripening. The diversion at this stage of development of the berries water supply from the peripheral to the axial xylem, and from the xylem system to the phloem system has important implications for the fruits ultimate mineral composition.

Characterization of genetic biodiversity with Vitis vinifera L. Sangiovese and Colorino genotypes by AFLP and ISTR DNA marker technology

Abstract: A comparison between two recently developed, PCR-based DNA marker technologies (amplified fragment length polymorphism, AFLP; inverse sequence-lagged repeat analysis, ISTR) was carried out in a group of 19 Vitis vinifera L. accessions, including 13 putative Sangiovese-related grapevines and 6 ''coloured'' ecotypes whose fruits are of importance for conferring intense red colour to the wine. A large amount of polymorphic DNA fragments was revealed by both molecular techniques: 8 different AFLP and 5 ISTR primer combinations generated 264 and 249 polymorphic markers, respectively. Similarity relationships among the accessions were described by cluster analysis. The AFLP analysis revealed the existence of a uniform group for the Sangiovese (SG) ecotypes showing a high degree of genetic relatedness for the members of this cultivar. Among the coloured ecotypes (CLR), variability was more evident. Only the so called Colorino americano ecotype significantly diverged from both groups. ISTR analysis confirmed the genetic dissimilarity of Colorino americano and the existence of the SG and CLR groups, but in addition detected a higher proportion of polymorphism among the Sangiovese accessions compared to AFLP analysis. Sangiovese forte and Saragiolo apparently differed from the other SG-related grapevines in agreement with AFLP results. It is possible that the observed genetic dissimilarity between Sangiovese forte, Saragiolo and other SG-related types could be interpreted by the putative polyclonal origin of many grapevine cultivars, a concept which is generally accepted by the grapevine research community. Both AFLP and ISTR appear to represent innovative, efficient and sensitive molecular tools for investigating genetic diversity among Vitis vinifera ecotypes and for the eventual identification of clones.

Elicitation and accumulation of stilbene phytoalexins in grapevine berries infected by Botrytis cinerea

Abstract: At three developmental stages berries of field-grown Castor (interspecific crossing) and Huxelrebe ( V vinifera L crossing) were in vitro inoculated with two strains of Botrytis cinerea Pers to investigate the response of berries to fungal infection With respect to the time course of phytoalexin (trans-resveratrol, e-viniferin and pterostilbene) accumulation and Visual disease symptoms In infected berries the amounts of e-viniferin dominated over pterostilbene The stilbene phytoalexin content decreased during berry development and sugar accumulation Grape varieties reacted differently to B cinerea strains with regard to stilbene response and Visual symptoms Mechanical damage of the berry skin induced uninfected berries to synthesize low amounts of phytoalexins It can be assumed that after extraction and degradation e-viniferin of mature berries is a source of resveratrol in wine

Influence of cluster exposure on fruit composition and wine quality of seyval blanc grapes

Abstract: Experiments were conducted in 1981 and 1982 to investigate the influence of duster exposure on fruit composition, wine quality, and incidence of bunch rot ( Botrytis cinerea PERS.) of the French-American hybrid grape cultivar Seyval blanc. Berry sampling from 4 exposure categories (western exposure, eastern exposure, partial shade, and full shade) indicated highest °Brix, pH and tartrate, and lowest titratable acidity (TA) and malate in the exposed fruit post veraison. Total acidity and malate were highest in exposed fruit between fruit set and veraison. Exposure of the fruit also reduced the incidence of bunch rot during the 1981 season. Wine quality differences were small and not statistically significant, although wines vinted from exposed fruit tended to score higher. Canopy management practices that optimize fruit exposure would be helpful in maximization of fruit and wine quality.

Pathogenicity of Botryosphaeria species isolated from declining grapevines in sub tropical regions of Eastern Australia

Abstract: From 2002 to 2004, vines from 11 vineyards in the Hunter Valley region and from 4 vineyards in Mudgee (New South Wales, Australia) were inspected for foliar and wood symptoms of Eutypa dieback and Botryosphaeria canker. Eutypa lata was not isolated, however species of Botryosphaeria were frequently isolated from dead and declining spurs, cordons and trunks. Two species conforming to the anamorphs of Diplodia and Fusicoccum were isolated. Cultures on PDA producing a yellow pigment, and hyaline aseptate conidia (14-23.5 x 8-13 μm in size) were identified as B. lutea. Cultures with dark brown, 1-septate, ornamented conidia (15-25 x 8-14 μm in size) at maturity were identified as B. obtusa . Pathogenicity tests were conducted on detached green shoots, detached one-year-old canes and glasshouse-grown grapevines. In all situations, disease symptoms were reproduced and Koch’s postulates were fulfilled. The results demonstrate the potential of B. obtusa and B. lutea as primary pathogens of Vitis vinifera .

Easy and accurate estimation of grapevine leaf area with simple mathematical models

Abstract: Empirical models for non-destructive estimation of primary and lateral leaf area are presented for cv. Aragonez, syn. Tempranillo. Primary leaf area of shoots is estimated by a model using a calculated variable obtained from the average of the largest and smallest primary leaf area multiplied by the number of primary leaves. For lateral leaf area estimation another model is presented which uses the same type of calculated variable plus the area of the largest leaf. Both models explain a high proportion of the leaf area variability and have a good predicting capability. Validation with 4 independent data sets periodically sampled during several seasons from different varieties shows that these models can predict primary and lateral leaf area independently of variety, year and growth stage, using a non-destructive, low cost, simple and accurate method. The models represent a powerful tool for grapevine research, for consultants and advanced growers allowing the evaluation of leaf area more frequently.

Inheritance of seedlessness in grapevine ( Vitis vinifera L.)

Abstract: Despite considerable efforts made by breeders for over 70 years, inheritance of seedlessness in grapevine is not clearly defined. None of the numerous hypotheses proposed until now is satisfying, whether they are based on recessive or dominant genes. We measured precisely the phenotypic expression of the seeded/seedless character in a progeny obtained by crossing two partially seedless selections and using in ovulo and in vitro culture to rescue embryos. We propose the hypothesis that inheritance of seedlessness in grapevine is based on a complex system whereby the expression of three independently inherited recessive genes is controlled by a dominant regulator gene. This hypothesis was compared to other results published in the scientific literature and appeared coherent enough to be used as a theoretical basis for further work on seedlessness inheritance in grapevine. Attempts to explain the control of seedlessness involve interactions with endogenous gibberellins. The consequences of such a model for the development of breeding programs for seedless table grapes, and particularly for the use of molecular biology techniques, are discussed.

Application of microsatellite markers to parentage studies in grapevine

Abstract: The use of microsatellites in genetic analysis does not only allow differentiation but also identification and parentage analysis of grapevine cultivars. Many of the cultivars which are of great economic importance, like Cabernet Sauvignon, have been selected and propagated centuries ago and often lack reliable documentation about their origins. In our study, 51 grapevine cultivars were genotyped at 24 microsatellite loci and searched for possible parent-offspring combinations. Our data confirm the origin of Cabernet Sauvignon from a cross between Cabernet franc and Sauvignon blanc. Furthermore we proved the parentage of the cultivars Neuburger (Silvaner x Veltliner rot), Blauburger (Portugieser blau x Blaufrankisch), Zweigelt (Blaufrankisch x St. Laurent) and Muller-Thurgau (Rheinriesling x Chasselas de Courtillier) at 24 SSR loci.

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

Abstract: 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.

Berry development of grapevines: Relations between the growth of berries and their DNA content indicate cell multiplication and enlargement

Abstract: DNA of berries (cv. Shiraz) was extracted and quantified to determine, indirectly, the rate of cell division and enlargement in the grape pericarp. The increase of total DNA in the pericarp begins at anthesis in the ovary of grapevine flowers (day 0, 100 % of flowers at full bloom). This increase in DNA continues during the herbaceous growth period until 35 d after anthesis (day 35, 19 d before the onset of veraison). Total DNA per berry pericarp does not increase linearly during this growth period since 75 % of the DNA has already accumulated before day 20. We determined a cell enlargement index (CEI), to estimate the mean cellular volume. The pericarp cell size increases 16-fold during the whole growth of berries. Volume increase is nearly linear from berry set to the beginning of veraison and thereafter until maturity. The importance of determination of cell division and enlargement of berry pericarp based on the DNA content and its possible application in studies on the influence of environmental factors on berry growth is discussed.

The soil effects on the grapevine root system in several vineyards of the Loire valley (France)

Abstract: The effects of different soil types on grapevine root distribution are presented and discussed for Loire Valley (France) conditions. Field studies with Cabernet franc/SO 4 root-stock vines showed four main rooting patterns in different soil types. A statistical analysis was used to determine the influence of several physical soil factors on root distribution. The soil water supply appears to have a beneficial effect on the root system. Conversely the penetrometer soil strength, bulk density and hydromorphic conditions are unfavourable for root development

Aroma components of Galician Albariño, Loureira and Godello wines

Abstract: Wines of the three most interesting Galician white grape varieties have been deeply analyzed for three aroma categories: the volatile compounds, except for monoterpenols, the monoterpenols and the bound forms. Many compounds showed significant differences between the wine groups, as proved by Tukey's test, e.g. for methanol, trans and cis 3-hexen-1-ols and relevant ratio, benzaldehyde and 4-vinylguaiacol in the first category, and for the most part of compounds of the other two categories. Loureira and most Albarino wines contain linalool and ho-trienol at a level of sensorial contribution. The relevant average terpene profiles show many similarities, especially for Albarino and particularly if considering the contents and relevant ratios of furan and pyran linalool oxide isomers, of ho-diendiols I and II and of geraniol. On the other hand differences could be stated for some compounds, mostly under the bound forms. Godello wines, with the poorest content of monoterpenols under both forms, are principally characterized by a marked level of bound benzaldehyde, with contemporary presence of a considerable average level of the free form. PCA data treatments on both monoterpenols and aglycons from the bound forms, showed a good separation among the groups as well a good homogeneity and varietal correspondence of the wines.

A simple model for simulation of growth and development in grapevine ( Vitis vinifera L.). 1. Model description

Abstract: A simple model for the simulation of growth and development of Sangiovese vines has been presented in a previous paper. In this paper the model is validated to examine whether the description of the physiological relationships in the model describe the growth of grapevine (cv. Sangiovese) realistically. Furthermore, the model was adapted and validated for the simulation of growth of another cultivar (cv. Cabernet Sauvignon). Comparisons of simulated and experimental data for both cultivars reveal that the model made good predictions of vine growth for the whole growing season.

The localisation of acids, sugars, potassium and calcium in developing grape berries

Abstract: Grape berries ( Vitis vinifera cv. Chardonnay) were divided into four concentric zones in order to follow the developmental changes in the concentrations of malate, tartrate, glucose, fructose, potassium and calcium within the skin and the fruit flesh. Green berries showed a definite malate gradient, increasing in concentration from the skin towards the seeds; tartaric acid, on the other hand, was highest in concentration at the periphery and lowest in the berry center. With progressing maturity, the ratio between the tartrate concentration in the skin and the corresponding values in the berry core decreased, whereas the reverse was true for malate. In the ripe berry an acid gradient could also be found in the axial direction, decreasing from the pedicel towards the stylar scar. Before the onset of ripening, the highest glucose and fructose concentrations were observed in the skin and the berry center. The accumulation of these sugars in the pulp began without any apparent lag phase at a rate of about 2 mg/ berry · d. After veraison, the highest concentrations were found in the fruit core and the tissue below the peripheral vascular bundles. Both potassium and calcium were mainly localized near the peripheral and central vascular bundles. The potassium content increased during the entire period of berry development at a constant rate of 0.04 mg/berry · d, whereas calcium accumulation stopped about 30 d after anthesis. At this time, the calcium content was approximately 0.1 mg/berry.

Situation de la vigne sauvage Vitis vinifera ssp. silvestris en Europe

Abstract: Cette contribution dresse un bilan de la repartition actuelle de la vigne sauvage europeenne - Vitis vinifera L. ssp. silvestris (Gmelin) Hegi - sur la base d'une revue bibliographique et d'observations originales effectuees lors de recherches sur son ecologie dans les forets alluviales et colluviales d'Europe. La situation de la vigne sauvage s'avere preoccupante dans la plupart des pays europeens, meme si elle est souvent mal connue, faute de donnees recentes fiables. La sous-espece silvestris se distingue essentiellement des cepages cultives par sa dioїcite. Les caracteres morphologiques vegetatifs sont tres variables; en particulier, on montre que le dimorphisme sexuel est manifeste dans les populations d'Autriche, alors qu'il n'est pas apparent dans celles du Pays Basque. Occurrence of the wild vine Vitis vinifera ssp. silvestris in Europe This paper summarizes the occurrence of the European wild vine - Vitis vinifera L. ssp. silvestris (Gmelin) Hegi - from bibliography and observations made in the framework of research on its ecology in the alluvial and colluvial forests of Europe. The state of the wild vine is disquieting within most of the European countries; in some countries we noticed a lack of recent reliable data. The subspecies silvestris can principally be distinguished from cultivated grapevine by its dioicity. Morphological vegetative criteria are very variable; in particular, we demonstrate that sexual dimorphism occurs in Austrian populations, while it is not found in those of the Basque countries.

A multiplex nested-PCR assay for sensitive and simultaneous detection and direct identification of phytoplasma in the Elm yellows group and Stolbur group and its use in survey of grapevine yellows in France

Abstract: Flavescence doree and Bois noir (or Vergilbungskrankheit), are two main yellows diseases of grapevines in Europe. The two diseases cannot be distinguished on the basis of symptoms but they are associated with two different phytoplasmas which belong to the Elm yellows (16SrV) group and Stolbur (16SrXII) group, respectively. Their spreading areas are overlapping in France, Italy and Spain but they have different vector insects. Flavescence doree is an epidemic disease and a quarantine organism. National surveys conducted annually in France require straightforward and sensitive assays to detect phytoplasma that sometimes occur in grapevine with a low titre and to characterize them readily. A bi-specific multiplex nested-PCR procedure was developed, to amplify simultaneously two non-ribosomal DNA fragments, 1150 bp and 720 bp in length, specific for Elm yellows-group and Stolbur-group phytoplasmas, respectively. They were identified using agarose gel electrophoresis of amplification products. The procedure is quick, sensitive and reliable. It was used on 2,525 grapevine samples from the field, in the frame of the French survey in 2002. Mixed samples containing both phytoplasmas displayed a mixed profile in the gel. It was confirmed that the nested-PCR amplimer obtained in the FD9 DNA region with Elm yellows-group phytoplasmas, though shorter than the initial FD9 fragment, nevertheless contained the restriction sites that permit the RFLP identification of geographic phytoplasma isolates already characterized in former studies.

Influence of leaf ageing, leaf area and crop load on photosynthesis, stomatal conductance and senescence of grapevine ( Vitis vinifera L. cv. Pinot noir) leaves

Abstract: Treatments varying the leaf area (source) to crop load (sink) balance of pot-grown Pinot noir vines caused differences in the photosynthesis (Pn) rates of the fourth leaf, 48 h after they were applied Stomatal conductance was only affected by leaf removal, not by the presence or absence of crop The vines with and without crop were subject to a range of leaf removal treatments All treatments retained leaves at nodes 1-4 from the shoot base and then had 100%(control), 66 %, 33 %, or 0 % leaves retained from node 5 to the apex of the shoot Leaf removal elevated the Pn rate of the fourth leaf, but there was no difference in Pn rate between vines with or without crop pre-veraison From veraison on the photosynthetic rate of vines with crop and 100 % leaves retained increased Similar, high Pn rate was also observed for vines without crop and 0 % leaves retained The lower Pn rate of vines with crop pre-veraison suggests that there is potential to increase vine productivity in this period The Pn rate of vines without crop, 100 % and 66 % leaves retained declined from 15 d after treatment Average Pn of all treatments over the 4 measurements prior to harvest was positively correlated with the vine leaf area (source) to total vine dry weight (sink) ratio Leaves of vines with a high source:sink ratio (without crop, 100, 66 or 33%leaves retained) senesced ie decreased in chlorophyll content more rapidly than leaves of the low source to sink ratio treatments Results indicate that the decline in grapevine leaf Pn, previously associated with advanced leaf age is actually caused by a progressive increase in leaf area to fruit weight (source:sink) ratio, as leaves emerge on the developing vine

Canopy microclimate modification for the cultivar Shiraz I. Definition of canopy microclimate

Abstract: Three treatments providing different canopy microclimates were applied to mature Shiraz grapevines at Gawler River 30 d before veraison. Constraining foliage into a smaller volume increased shading over control vines, and GDC training and slashing reduced it. Measurements demonstrated significant differences in terms of fruit exposure to solar radiation. Effects on microclimate due to vine vigour were also noted. A K balance made on vine shoots demonstrated that shade was associated with increased K concentrations in the leaves, petioles and stems at veraison. A visual scoring system of microclimate and growth characteristics was evaluated, and results correlated weil with microclimate measurements. A conceptual model is proposed to: explairi how soil and climatic factors and cultural decision can affect canopy microclimate.

A model analysis of the photosynthetic response of Vitis vinifera L. cvs Riesling and Chasselas leaves in the field: I. Interaction of age, light and temperature.

Abstract: The photosynthetic activity (A) of leaves of different ages on primary and secondary shoots of Riesling and Chasselas vines was measured under field conditions in relation to photon flux density (PFD) at various leaf temperatures. The data sets from 4 years and two locations (Geisenheim, Germany; Changins, Switzerland) were analysed using non-linear regression models to determine possible genetic and/or climate-induced differences in the light and temperature response between different leaf ages. A non-rectangular hyperbola with physiologically meaningful parameters was found to adequately describe the response to photon flux density. For both varieties, maximum photosynthetic rates were observed on leaves of primary shoots, opposite to the clusters, at a leaf temperature of 27-32 °C and at light saturation. Young leaves showed a less pronounced temperature optimum. The light response curves of photosynthesis of the two cultivars were similar over a temperature range of 20-30 °C. Below this temperature, Riesling showed higher values of A than Chasselas in most cases, whereas it was the reverse when leaf temperature exceeded 30 °C. This was particularly evident for leaves on secondary shoots and was related to differences in the photorespiration rate. Mature Riesling leaves had higher apparent quantum yields (a) and lower light saturation indices (Is) than Chasselas at leaf temperatures below 30-35 °C. Dark respiration (RD) and the light compensation point (Ic) responded strongly to temperature with differences between leaf ages but no consistent difference between varieties. Leaves on secondary shoots of both cultivars had the highest photo-synthetic activity during the ripening period of the fruit.