English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Viticulture in Michigan is often limited by cool and humid climate conditions that impact vine growth and the achievement of adequate fruit quality at harvest. Sugars, pH, acids, and yeast available nitrogen (YAN) are indices of quality and, as such, of suitability for wine production. The aim of this study was to evaluate the efficacy of foliar nitrogen (N) fertilization applied as a 1% w/v urea solution at veraison as a method to increase canopy N availability during the fruit ripening stage. To test the effect on different source sink conditions, we imposed three levels of defoliation (0%, 33%, and 66% of leaves removed per vine) and measured net photosynthetic rate (Pn), leaf efficiency parameters, yield components, and fruit quality parameters. Apical leaf Pn was increased by the 33% defoliation (+12% from the undefoliated control) and by the urea application (+6%) 2 weeks after veraison. In basal leaves we observed a reduction in chlorophyll content (SPAD) and maximum photochemical efficiency of PSII (Fv/Fm) as a result of the defoliation treatment and secondarily by the N application, which resulted in a reduction in Pn. Therefore, mean shoot Pn was unaffected by the treatments. Although neither main nor lateral shoot growth was increased by any defoliation treatment, both percent soluble solids (%SS) and berry weight were significantly reduced by the 66% defoliation treatment. Application of urea increased yeast available amino acids by 20% but did not impact %SS or other chemical parameters indicating a different accumulation pathway for sugars and amino acids in the berry. Nitrogen is quantitatively the most important mineral nutrient for grapevine growth and reproduction (Keller, 2010) and its use as a fertilizer impacts canopy efficiency and fruit growth and maturation (Jackson and Lombard, 1993). During canopy development, adequate N supply is used in the leaves to maintain high levels of chlorophyll and proteins, like Rubisco, inside the chloroplasts. N availability is correlated with the net Pn of the canopy (Keller, 2005). Importantly, leaves are not the exclusive sink for mineral N, because it is partitioned among different vine organs at different stages of grapevine development (Conradie, 1990). The total content of berry N increases linearly through the full cycle of berry growth. However, the accumulation of total free amino acid in the berries increases at the onset of veraison and contributes to the pool of YAN, which includes N in the form of a-amino acids and ammonia (Bell and Henschke, 2008). This latter accumulation pattern is quite variable across different grape cultivars (Kliewer, 1968; Rodriguez-Lovelle and Gaudillère, 2002). A low level of YAN in grape must frequently occur in grape cultivars grown under cool climate conditions (Löhnertz et al., 1998) and it is often associated with sluggish-stuck fermentations (Spayd et al., 1995). Low YAN can also lead to the production of off-flavors in wine (Bell and Henschke, 2008). Aside from nutrient availability, the Pn of the canopy through the growing season is tied to the vine’s sink demand for carbohydrates, driven by both vegetative and reproductive growth. Therefore, manipulation of the source sink ratio can affect grapevine Pn (Edson et al., 1993). A reduced leaf area or a reduced ratio between leaf area and sink, i.e., cluster numbers or size, have resulted in higher rates of Pn (Hunter and Visser, 1988; Palliotti et al., 2011; Poni et al., 2008). Although an increase of photosynthesis can compensate for the loss of source availability during fruit development and ripening (Candolfi-Vasconcelos and Koblet, 1991), a compensatory effect can also result from a change in the aging process of the leaves. Older leaves of the canopy, generally corresponding to leaves in the fruit zone, decrease their Pn after they reach full development (Poni et al., 1994). It has been observed that older leaves can maintain a higher Pn when a source reduction is imposed (Petrie et al., 2000b). Because cluster demand for photosynthates varies among different stages of development, the response to defoliation can also vary according to phenological stage. For example, an increase in photosynthesis at veraison, independent of sink size, was also observed (Petrie et al., 2003). The objective of this study was to determine the effect of foliar applied N at veraison in relation to source limitation imposed during fruit maturation. In particular, the hypotheses of our study were: N applied at veraison 1) influences vine performance (yield, fruit chemistry composition, and vine productivity); 2) impacts Pn and the leaf aging process; and 3) influences N content of the berries in the form of yeast available amino-N. Materials and Methods Vineyard site. The experiment was conducted in 2011 at Michigan State University’s Southwest Michigan Research and Extension Center in Benton Harbor, MI (lat. 42 05#10.55$N, long. 86 21#03.68$W). Michigan’s climate is characterized by a short growing season (145 to 175 d) with cool climate summer conditions [1200 ± 300 growing degree days (GDD)] calculated beginning 1 Apr. through 31 Oct. using the base 10 C standard. Climatological data were recorded during the experiment by an automated weather station of the Michigan Automated Weather Network located 200 m from the experimental vineyards (Fig. 1). The 2011 growing season was characterized by 1485 GDD (Baskerville and Emin, 1969) until the end of September, a warm season when compared with Michigan’s average annual GDD accumulation (1200 ± 300) (Howell and Sabbatini, 2008). Precipitation in the amount of 545 mm was uniformly spread through the season, showing the classical rainy events in the spring [ 100 to 120 day of the year (DOY)] and at harvest ( 240 to 270 DOY) characteristic of cool climate viticulture in the Great Lakes region of the United States. Plant material. ‘Chardonnay’ grapevines (clone Colmar) were planted in 1990 in a Spinks loamy fine soil (U.S. Department of Agriculture, Soil Conservation Service, 1957), grafted on C3309 rootstock, with spacing of 1.8 m in the row 3 2.7 m between rows with rows oriented north to south. Vines were cane pruned during the winter of 2010 to 35 nodes Received for publication 29 Nov. 2012. Accepted for publication 24 Mar. 2013. This research was partially supported by AgBioResearch at Michigan State University (Project GREEEN), the Michigan Grape and Wine Industry Council, and the MSU Southwest Michigan Research and Extension Center. We appreciate the assistance of P. Murad, D. Acimovic, and S. Zhuang in collecting data; of D. Francis for his help in vineyard maintenance; and of A. Green for critical reading of the manuscript. To whom reprint request should be addressed; e-mail sabbatin@msu.edu. 608 HORTSCIENCE VOL. 48(5) MAY 2013 per vine or 19 nodes per meter of row and trained to vertical shoot positioning with a fruit-bearing wire 1.2 m from the ground and there were three sets of catch wires at 40-cm intervals from the fruit-bearing wire. For the 3 years ending with the 2011 growing season, no irrigation or fertilizers were applied to the experimental plot. Soil analysis was performed before bloom and nutrient levels (N: 1.2 g·kg; phosphorus: 154 ppm; potassium: 135 ppm; magnesium: 74 ppm; calcium: 528 ppm) were considered sufficient according to vineyard management practices of the eastern United States (Bates and Wolf, 2008; Wise et al., 2008). Clusters per vine were counted 2 weeks after fruit set and clusters thinned to achieve homogeneity of cropping conditions across blocks. Lateral shoots were removed as emerged from the fruiting zone and shoots exceeding the height of the trellis were topped to 30 cm above the last set of catch wires 2 weeks before veraison. Treatments and experimental design. The experiment was designed as a randomized complete block with three blocks and these two factors: 1) intensity of defoliation performed at veraison (initial berry softening or Stage 35 as described by Eichhorn and Lorenz, 1977); and 2) application of foliar N fertilizer. Each combination of the different levels of the two factors was randomly assigned to three vines (replications) within each block. Defoliation was performed manually at three levels: control undefoliated (no leaves removed, ‘‘CUD’’), 33% (one leaf every three nodes, ‘‘33D’’), or 66% (two leaves every three nodes from each shoot, ‘‘66D’’) of total leaves. Vines designated to be treated with foliar N (TN) were sprayed with a urea solution (1% w/v) using a backpack sprayer to the whole vine canopy until runoff, whereas control vines (CN) were left unsprayed. Direct spraying of the clusters was avoided. Because number of leaves and, consequently, leaf area were variable within different defoliation treatments, the total amount of urea per vine varied as well. Based on volume of solution applied on non-defoliated vines (CUD + TN) of each block, we estimated that 17 g ± 2 SD of urea was applied on these vines. Data collection. On each vine, five modal shoots bearing 1.6 ± 0.2 SD clusters were selected and tagged 2 weeks before veraison. The length of each tagged shoot was measured before treatment application. The number of lateral shoots and their lengths were also recorded. Measurements were repeated 1 week before veraison and 3 weeks after veraison. Total lateral shoot growth was calculated as the sum of lateral length increases from 1 week to 3 weeks after veraison. Leaf area (LA) of the five tagged shoots was estimated using the methodology described by Poni et al. (2008). Random shoots (n = 20) from guard vines were collected 2 weeks before veraison and the linear regression between shoot length and total leaf area (y = 17.04x + 165.25, R = 0.94) was calculated and then used to estimate LA per shoot. On defoliated vines (33D and 66D), leaves removed at veraison were collected and LA measured with a LI-3100C area meter (LI-COR, Lincoln, NE). LA at veraison w

hortscience

Increasing Nitrogen Availability at Veraison through Foliar Applications: Implications for Leaf Assimilation and Fruit Ripening under Source Limitation in ‘Chardonnay’ (Vitis vinifera L.) Grapevines