Yield, fruit quality, bud fertility and starch reserves of the wood as a function of leaf removal in Vitis vinifera-Evidence of compensation and stress recovering

Einfluß unterschiedlicher Entblätterung auf Ertrag, Traubenqualität, Knospenfruchtbarkeit und Stärkegehalt des Holzes von Vitis vinifera sowie Kompensations- und ErholungsvermögenAn Ertragsreben wurde der Einfluß des Entfernens von Hauptblättern oder Geiztrieben auf Gesamtblattfläche, Traubenertrag und -qualität sowie Stärkegehalt des Holzes studiert. Die Bedeutung von Haupt- und Geizblättern sowie des Zeitpunktes der Entblätterung auf dss Verrieseln wurde untersucht. Ziel der Studie war, Kompensationsmechanismen und -limiten der Rebe unter Streßbedingungen kennenzulernen, wie sie durch eine Entblätterung verursacht werden. Ferner sollte die Erholung der Pflanze nach längerer Streßeinwirkung erforscht werden.Wurden die Hauptblätter entfernt (L = nur Geizblätter}, so bildeten die Pflanzen mehr Geiztriebe mit einer größeren Anzahl Blätter. Dies führte nach dem ersten Streßjahr zu einer ungefähr gleichen Gesamtblattfläche wie bei den Kontrollpflanzen. Nach einem weiteren Streßjahr jedoch hatten die L-Pflanzen zwar weiterhin mehr Geizblätter, allerdings von geringerer Größe. Hieraus resultierte eine im Vergleich zur Kontrolle verringerte Gesamtblattfläche. Pflanzen nur mit Hauptblättern (M) kompensierten das Fehlen der Geiztriebe mit verzögerter Blattalterung und späterem Blattfall. Auch hier ergab sich nach dem zweiten Streßjahr eine geringere Blattgröße. Der Traubenertrag der L-Pflanzen wurde im 1. Jahr durch die Blattentfernung kaum negativ beeinflußt, aber im 2. Jahr war er 50 % niedriger als in der Kontrolle. Bei den M-Pflanzen ergab sich in beiden Jahren kein verringerter Ertrag. Der Zuckergehalt der Trauben war in den L-Pflanzen im 1. Streßjahr leicht erhöht, nicht aber im 2. Jahr. Diese Reben hatten während beider Jahre eine bessere Beerenfarbe.Die Blattfläche vom Zeitpunkt der Blüte bis 2-3 Wochen danach ist für den Traubenertrag entscheidend. Eine Entblätterung zu diesem Zeitpunkt verursachte nicht nur ein Verrieseln, sondern im folgenden Jahr zusätzlich eine reduzierte Knospenfruchtbarkeit. Die Zuckereinlagerung in den Trauben hängt von der assimilierenden Blattfläche während der Reifeperiode ab. Der Stärkegehalt im Holz war nach 2 Streßjahren erheblich reduziert. Es ergaben sich schwach positive Korrelationen zwischen Zuckergehalt des Mostes und Stärkegehalt des Holzes.Die Zuckereinlagerung in die Traube und das Auffüllen der Stärkereserven im Holz ging bereits in der auf eine Streßbehandlung folgenden Saison normal vonstatten. Ein normaler Ertrag war l Jahr nach einem längeren Entblätterungsstreß jedoch noch nicht möglich, da die Bildung der Infloreszenzen bekanntlich während dieser Zeit (in unserem Fall die Streßperiode) einsetzt. Erst im 2. Jahr kam es zu einer vollständigen Erholung der Pflanze

Influence of partial defoliation on gas exchange parameters and chlorophyll content of field-grown grapevines - Mechanisms and limitations of the compensation capacity

In order to study the compensation mechanisms related to leaf removal, gas exchange response to defoliation as well as chlorophyll content were investigated in field-grown Pinot noir grapevines. Mature 16 years old bearing plants and 2 years old fruitless potted plants were compared. Defoliation treatments were performed 1 week after full bloom. Besides topping, three levels of main leaf removal (3, 6 or all 12 main leaves retained) were combined with two levels of laterals (all retained or all removed). The single leaf measurements (on the 11th main leaf from the base) were carried out from treatment time to fruit maturity

Assessment of risk of insect-resistant transgenic crops to nontarget arthropods

An international initiative is developing a scientifically rigorous approach to evaluate the potential risks to nontarget arthropods (NTAs) posed by insect-resistant, genetically modified (IRGM) crops. It adapts the tiered approach to risk assessment that is used internationally within regulatory toxicology and environmental sciences. The approach focuses on the formulation and testing of clearly stated risk hypotheses, making maximum use of available data and using formal decision guidelines to progress between testing stages (or tiers). It is intended to provide guidance to regulatory agencies that are currently developing their own NTA risk assessment guidelines for IRGM crops and to help harmonize regulatory requirements between different countries and different regions of the world

Influence of the twospotted spider mite, Tetranychus urticae, on the gas exchange of Pinot noir grapevine leaves

The effect of feeding damage by the twospotted spider mite (Tetranychus urticae KOCH; Acari: Tetranychidae) on the gas exchange of grapevine leaves (Vitis vinifera L.; cv. Pinot noir) was investigated. In addition, the influence of some pesticides was studied. A significant reduction of the net CO2 assimilation, transpiration as well as stomatal and mesophyll conductance with increasing mite feeding damage were observed. At 6000 mite-days per leaf the 3rd and 9th main leaves (from the base) showed an average reduction in net CO2 assimilation of 52.2 % and 48.4 %, respectively, while the 6th leaf showed a reduction of only 21.3 %. The response of grapevine photosynthesis to mite feeding seems to depend not only on mite density and duration of feeding, but also on the phenological stage of the plant. In fact, at veraison the vines showed increased tolerance to mite feeding compared with other phenological stages. At mite infestation levels of 6000 mite-days, leaves infested with T. urticae showed, as compared to uninjured leaves, an average reduction in transpiration rate of 14.4 % to 40.8 %, depending on the leaf position. The acaricides Tetradifon and Fenbutatin-oxide and the fungicide Folpet combined with Penconazol showed no effect on the gas exchange parameters

Effects of Crop Level on Fruit Composition of Pinot noir Grapes

A broad range of factors influences wine grape quality and its manipulation has stimulated interest among grape growers, wine makers, and research scientists alike. One such factor affecting wine grape quality is crop level, particularly for Pinot noir. Since the capacity of a vine to ripen fruit depends largely on the rate of photosynthesis and accumulation of carbohydrates, it follows that a quantitative crop level may be related qualitatively to fruit composition

Cooperative Rootstock Trials: Research Update

Five replicated rootstock trials established in Oregon's three main viticultural regions were evaluated for the effect of rootstock on Pinot noir performance. All the trials except Alpine included the following seven rootstocks: ungrafted Pinot noir, 3309 Couderc, 101-14 Millardet et De Grasset, 44-53 Malegue, 420 A Millardet et De Grasset, 5 C Teleki, and Harmony. At Alpine, the rootstock selection included ungrafted Pinot noir, 3309 Couderc, 101-14 Millardet et De Grasset, Riparia Gloire, Selection Oppenheim 4 (SO 4) and Kober 5BB. Rootstock effect on scion performance varied greatly with site, and the responses typically were not consistent from site to site. At Newberg, Pinot noir grafted to 420 A had the best yields and ungrafted vines, the lowest. Vines grafted to 101-14 had the highest must soluble solids. At Lafayette, no rootstock differences in soluble solids in the juice could be observed but yields were better with 3309 C. At Umpqua, the most vigorous site, vines grafted to 45-53 had the best yields and when grafted to 101-14 had the lowest fruit production. There was no difference on must soluble solids at this site. At Eagle Point, a site with very shallow soil and low vigor, yields were better when vines were grafted to 3309 C and lower when grafted to Harmony or 5C. Must soluble solids did not respond to rootstock. At Alpine, with a different selection of rootstocks, yields were better when the stock was SO 4 but there was no rootstock effect on Brix

Evaluation of varieties, clones, and rootstocks: II. & III. Performance of Pinot noir and Chardonnay clones : 1997-1998

Pinot noir and Chardonnay are the two main winegrape varieties in Oregon. In 1997, they comprised approximately 58% of the Oregon winegrape acreage, and 60% of the total production for a value of $14,171,000 (66% of total) (1). Internationally, clonal selection of Pinot noir and Chardonnay have made available, for each variety, an array of clones with wide ranging levels of productivity and fruit quality. In the Champagne region, clones were selected for increased yields; in Burgundy, the main criterion was high fruit quality; and in Switzerland, the Pinot noir clone Mariafeld was selected for disease resistance. In the U.S., clones selected here and elsewhere continue to be evaluated for their suitability to local growing conditions. The Pinot noir clones included in the trial at Woodhall III Vineyard (Table 1) include representatives of diverse types loosely classified into four groups: 1) Pinot fm, typically characterized by having small clusters and prostrate growth habit; 2) Mariafeld, most noted for having loose clusters; 3) Upright, known for their erect growth habit; and 4) Fertile, typically having large clusters and prostrate growth habit (2). The Chardonnay clones at Woodhall III Vineyard (Table 2), although not as numerous as clones in the Pinot noir trial, also represent a range of types with different levels of productivity and fruit quality

Evaluation of varieties, clones, and rootstocks: I. Evaluation of phylloxera-resistant rootstocks for the cultivars Pinot noir, Chardonnay, Pinot gris and Merlot : 1998-1999

With new vineyard planting and the replanting of older vineyards on phylloxera-resistant rootstock on the rise, grape growers are looking for rootstocks that are good fits for a particular site and management style. Making an informed decision on rootstocks before planting can help create a vineyard that will be manageable and profitable. Factors such as vigor, sunlight use efficiency and water transpiration can be useful in evaluating which rootstock might be appropriate for a site with certain limitations or abundance. Side-by-side analysis of rootstocks can help in determining which rootstock has desirable or undesirable traits for a chosen need. The new rootstock experimental block at the Woodhall III vineyard was planted in the summer of 1997 and includes a trial of Pinot noir (clone FPMS 2A) grafted on nineteen rootstocks plus an own- rooted control. Another trial consisting of Pinot noir (clone FPMS 2A), Chardonnay (clone Dijon 95), Merlot (clone FPMS 3) and Pinot gris (clone Colmar 146) was planted, all four varieties grafted onto nine rootstocks and an ownrooted control. This report summarizes the analysis of the physiological growth responses during the 1998 growing season

Pathogenicity and Management of Plant-Parasitic Nematodes on Vitis vinifera in Oregon Vineyards : 1998-1999

Plant-pathogenic nematodes that cause yield loss in California and European vineyards are found in over 85% of Oregon vineyards. Population densities of Xiphinema americanum (dagger nematode) and Criconemella xenoplax (ring nematode) were found in 37% of vineyards at levels reported to cause 10-25% loss in California vineyards. However, these nematode species were rarely associated with poor vine vigor in Oregon vineyards. It is unclear whether established vineyards will succumb to nematode damage over time or if the high vigor of vines in Oregon allow them to compensate for damage caused by nematodes. Even if older vines can withstand nematode parasitism, vines replanted in infested soil with high population densities of plant-parasitic nematodes may not fare as well. The objectives of this research are: 1) to determine the relationship between nematode densities and vine health and yield in established and in new or replanted vineyards, 2) to ascertain what conditions, such as management inputs, climatic, or site characteristics, influence this relationships, 3) to evaluate techniques for managing nematode populations and nematode injury to vines, including resistant rootstocks, cultural practices, biological control, and nematicides which are labeled on grape

Evaluation of phylloxera-resistant rootstocks for the cultivars Pinot noir, Chardonnay, Pinot gris and Merlot

Vineyard acreage in Oregon continues to increase at a rapid pace. In the past two years alone 1600 acres of new vineyard land have been planted (Rowley et al., 2000). Much of this has been on phylloxera-resistant rootstocks. This practice is strongly encouraged, since it is the only practical way of dealing with this pest. At the same time, established vineyards in the state that have been affected by phylloxera are being replanted onto rootstocks. Although planting on rootstocks is more expensive than planting own-rooted vines, it also provides the grower an opportunity to control vine vigor and affect fruit composition. Unfortunately there is little data specific to Oregon, on which the grower can base his or her choice of rootstocks. In order to fulfill this need, an experiment was begun in 1997 to evaluate the performance of 19 different rootstocks, onto which four different varieties were grafted. This experiment is being conducted at Oregon State University's Woodhall III Vineyard, five miles west of Alpine, Oregon. The data presented here is from this experiment and was collected during the 2000 growing season