Influence of leaf area density and trellis/training system on the light microclimate within grapevine canopies

The influence of leaf area density and canopy configuration on the light microclimate within 6 wine grape trellis/ training systems commonly used in California (single curtain, double curtain, vertically shoot positioned, lyre, Smart-Henry and Smart-Dyson) was examined in two experimental vineyards (Oakville and Parlier). Mean canopy leaf area density varied considerably among the systems, ranging from approximately 2.8 m2m-3 for the Wye to 10.1 m2m-3 for the VSP. Non-positioned systems were characterized by a layer of relatively high leaf area density in their outer envelope and lower leaf area densities in their interior. In contrast, leaf area density in positioned systems increased from the top of the canopy moving downward to the fruit zone. Mean leaf area density within the fruit zone ranged from near 6 m2m-3 in the DC to over 12 m2m-3 in the VSP and LYR. The pattern of light attenuation within the canopy was generally similar among the systems, with PPF reaching its lowest level in or near the fruit zone. Fruit zone PPF was >10 % of ambient sunlight in low density canopies and <5 % in high density canopies. A gradual decline in fruit zone PPF was found as leaf area density increased in positioned systems. PPF decreased sharply in the fruit zone of non-positioned systems as leaf area density increased from 2 to 4 m2m-3, then leveled as leaf area density exceeded 6 m2m-3. Fruit zone PPF decreased as the leaf area density of divided systems increased from 2 to 4 m2m-3, then declined gradually as leaf area density approached 6 m2m-3. Fruit zone PPF in non-divided systems was initially lower, and declined more gradually as leaf area density increased, compared to divided systems. Compared to positioned systems, leaf layer number in the fruit zone rose more sharply in non-positioned systems as leaf area density increased. Leaf layer number was greater in nondivided systems compared to divided systems, but declined at similar rates in both systems as leaf area density increased. Shoot-positioned systems achieved well-exposed fruit zones at higher leaf area densities, but lower leaf layer numbers, compared to non-positioned canopies

Chilling requirements and dormancy evolution in grapevine buds.

Fluctuations in winter chilling availability impact bud dormancy and budburst. The objective of this work was to determine chilling requirements to induce and overcome endodormancy (dormancy controlled by chilling) of buds in different grape cultivars. "Chardonnay", "Merlot" and "Cabernet Sauvignon" shoots were collected in Veranópolis-RS vineyards in 2010, and submitted to a constant 3 °C temperature or daily cycles of 3/15 °C for 12/12h or 18/6h, until reaching 1120 chilling hours (CH, sum of hours with temperature ≤ 7.2 °C). Periodically, part of the samples in each treatment was transferred to 25 °C for budburst evaluation (green tip). Chilling requirements to induce and overcome endodormancy vary among cultivars, reaching a total of 136 CH for "Chardonnay", 298 CH for "Merlot" and 392 CH for "Cabernet Sauvignon". Of these, approximately 39, 53 and 91 CH are required for induction of endodormancy in the three cultivars, respectively. The thermal regimes tested (constant or alternating) do not influence the response pattern of each cultivar to cold, with 15 °C being inert in the CH accumulation process. In addition, time required to start budburst reduces with the increase in CH, at a rate of one day per 62 CH, without significant impacts on budburst uniformity. Index terms: Chilling hours; endodormancy; budburst; Vitis vinifera

Does delaying the rate of ripening alter aroma compounds?

Climate change has resulted in accelerated grape ripening which can lead to poor colour and aroma development. Prolonging grape maturation until optimal phenolic and aroma compounds are achieved is commonly used to counteract this trend. Researchers evaluated whether this technique produces grapes with less sugar and more aroma compounds.Pietro Previtali, Nick Dokoozlian, Bruce Pan, Kerry Wilkinson and Christopher For

Seasonal and regional variation of green aroma compounds in commercial vineyards of vitis vinifera L. Merlot in California

A field study was conducted from 2007 to 2010 to examine regional and seasonal variability of the main compounds responsible for green aromas in grapes and wines, 3-isobutyl-2-methoxypyrazine and C6 compounds. Sixty-nine commercial Vitis vinifera L. Merlot vineyards located in three distinctly different winegrape growing regions within the Central Valley of California were sampled at commercial harvest, fruit samples were analyzed for green aroma compounds and standard chemometrics, and several weather parameters such as growing degree days and rainfall were recorded at the vineyard level. Seasonal variation was found to be more important than regional variation, and similar trends among regions were found within each season. Temperature during the spring, a period of active growth, was found to be a significant driver of fruit green aroma compounds at harvest, likely due to its interactions with vine vigor and fruit shading. © 2013 by the American Society for Enology and Viticulture. All rights reserved.Martin P. Mendez-Costabel, Kerry L. Wilkinson, Sue E.P. Bastian, Michael McCarthy, Chris M. Ford, and Nick Dokoozlia

Effect of winter rainfall on yield components and fruit green aromas of Vitis vinifera L. cv. Merlot in California

Article first published online: 25 DEC 2013impact of winter rainfall on the main compounds responsible for green aromas in grapes and wines, 3-isobutyl-2-methoxypyrazine (IBMP) and C6 compounds. These compounds are considered undesirable in grapes and wines above the threshold concentration. Methods and Results: One treatment subjected vines to average rainfall, while the other excluded winter rainfall by covering the ground with a plastic tarpaulin during the entire dormant season (November to mid-March). Irrigation for both treatments was maintained at a weekly rate of 70% of crop evapotranspiration until commercial harvest. Canopy growth, berry size and vine yield were significantly reduced by rainfall exclusion, and a significant increase in the fruit to pruning mass ratio was recorded from one season to another. Synthesis of IBMP was significantly greater in vines under normal rainfall, whereas C6 compounds were significantly different between treatments only at the end of the second season. Fruit and wine composition, mainly colour and mouthfeel compounds, were positively affected by the absence of rainfall in both years. Wine descriptive analysis showed that the lack of rainfall produced wines perceived as less green and of more intense fruit attributes in the first season. As a consequence of the reduction in vine growth, however, the same treatment produced wines less intense in fruit aromas and of inferior tannin quality in the following season. Conclusions: These results show that the soil moisture level prior to budbreak affects both canopy growth and vine yield, even when irrigation is applied following budbreak. If the rainfall level is below normal, the positive effect on fruit and wine composition achieved through smaller berry size may be offset by a significant reduction in canopy growth, resulting in severely unbalanced vines, i.e. inadequate fruit to pruning mass ratio. Significance of the Study: Growers aiming to minimise the level of IBMP at harvest would benefit from applying moderate deficit irrigation and nitrogen fertilisation rates and also might achieve an earlier harvest date for those vineyards where the absence of undesirable vegetal characters is considered a key harvest metric.M.P. Mendez-Costabel, K.L. Wilkinson, S.E.P. Bastian, C. Jordans, M. McCarthy, C.M. Ford and N. Dokoozlia

Efeitos do CPPU e GA3 no cultivo de uva-'Itália' na região do submédio São Francisco, nordeste do Brasil Effect of CPPU and GA3 in grapes 'Itália' in Submedium São Francisco River Valley region, northeast Brazil

Na região do submédio do São Francisco, a uva-'Itália' destaca-se com 63,2% da área total plantada. Atualmente, é a principal variedade para exportação. O objetivo principal deste trabalho foi avaliar o efeito das doses do CPPU (forchlorfenuron) e GA3, no aumento do tamanho da baga, que foram aplicadas por meio de pulverização dirigida sobre os cachos durante a fase de pegamento dos frutos, quando as bagas haviam atingido, aproximadamente, 8 mm de diâmetro. Este experimento foi conduzido na Fazenda Cooperyama, no município de Juazeiro-BA. O delineamento experimental foi o inteiramente casualizado, com oito tratamentos e três repetições, avaliando-se 15 cachos por tratamento com as seguintes doses: 1- Testemunha absoluta; 2- GA3 20 mg/l;3- GA3 20 mg/l+ CPPU 3 mg/l; 4- GA3 20 mg/l + CPPU 5 mg/l; 5- GA3 20 mg/l + CPPU 10 mg/l; 6- CPPU 3 mg/l; 7- CPPU 5 mg/l; 8- CPPU 10 mg/l.O melhor resultado obtido no crescimento da baga deu-se com a aplicação do CPPU 10 mg/l. Este tratamento diferiu significativamente da testemunha e da aplicação convencional com GA3 20 mg/l, aumentando 8% e 4,6% o comprimento da baga, 13,6% e 7,3% sua largura, e o peso de baga em 32% e 16,3%, respectivamente. Nos tratamentos com CPPU aplicado isoladamente e/ou associado com GA3, a colheita foi retardada em oito dias. Não se verificou diferença significativa para os teores de sólidos solúveis; no entanto, foi constatado que a acidez titulável obteve valores mais elevados na testemunha e no tratamento com GA3, aplicando 20 mg/l. Com relação ao peso do engaço, não foi verificada diferença estatística entre os tratamentos.<br>The Itália grape cultivar participates with 63,2% of the total growing area in Submedium São Francisco River Valley it's the main variety for exportation. The main objective in this work was to evaluate the effect of CPPU (forchlorfenuron) and GA3 doses on the berry size increase. The products were applied by spraying them on the bunches during the fruit-set stage when the berry size was about 8 mm in diameter. The experiment was done in Cooperyama farm in Juazeiro-BA, Brazil. The experimental design was choosed at random with 8 treatments and 3 repetitions, evaluating 15 bunches per treatment with the following doses: 1- Control; 2- GA3 20 mg/l;3- GA3 20 mg/l+ CPPU 3 mg/l; 4- GA3 20 mg/l + CPPU 5 mg/l; 5- GA3 20 mg/l + CPPU 10 mg/l; 6- CPPU 3 mg/l; 7- CPPU 5 mg/l; 8- CPPU 10 mg/l. The best result in the berry growth was with CPPU 10 mg/l. This treatment differed significantly from the control and from GA3 20 mg/l (the conventional treatment) increasing the berry length in 8% and 4,6%; 13,6% and 7,3% its width and the berry weight in 32% and 16,3 % respectively. In the treatments with CPPU applied alone and/or associated with GA3 the harvest was delayed in eight days. We could not find significative differences in soluble solids rates, but we found that the titrable acidity showed the highest values in the control and in the treatment with GA3 20 mg/l. About the stalks weigh we could not find statistical differences between the treatments