Effects of cane-and spur-retained node numbers on the pre-flowering vegetative growth of cane-pruned Sauvignon blanc

In established vineyards, node number retention at winter pruning is the first step to achieving and maintaining vine balance. Balanced vines exhibit timely and quasi-uniform 100 percent budburst. To understand how vine capacity and balance are expressed before flowering, mature Sauvignon blanc vines were pruned according to a 5 [total node numbers on canes: 10, 20, 30, 40, 50] x 3 [total node numbers on spurs: 1, 2, 3] factorial design in one site, and in two other sites according to a 5 [total node numbers on canes: 10, 20, 30, 40, 50] x 2 [total node numbers on spurs: 1, 2] factorial design. Two spurs of one, two or three nodes each were retained on either side of the vine. The number of canes laid down per vine was one, two, three and four canes each of 10 nodes for the 10-, 20-, 30-and 40-node treatments, and four canes averaging 12.5 nodes for the 50-node treatment. The budburst percentage was calculated on the whole vine, canes, and spurs. Blind nodes, count shoots, non-count shoots and double shoots were counted and mapped along canes and spurs. Many non-count shoots were measured on the vine head of 10-node vines (29.5 ± 3.0 shoots, p < 0.001), compared to 50-node vines (2.8 ± 1.9 shoots, p < 0.001). 50-node vines had an overall budburst of 100 %, despite having the highest number of blind nodes (7.6 ± 0.3 nodes, p < 0.001). These were mainly located at the canes’ proximal sections relative to the vine head and were likely caused by correlative inhibition and primary bud necrosis. Cane budburst provided a more accurate assessment of the vine response to node loading than vine budburst. The number of double shoots was not associated with the vine node load, as they appeared on both low-node and high-node vines. Three-node spurs developed more blind nodes than one-node and two-node spurs (p < 0.001). Based on the findings of this research, we recommend a composite metric (cane percent budburst, cane blind node count and head shoot count) to assess vine capacity and balance between budburst and flowering, and the practice of retaining one-or two-node spurs at cane pruning is also justified

Effect of pruning system, cane size and season on inflorescence primordia initiation and inflorescence architecture of Vitis vinifera L. Sauvignon Blanc

Background and Aims: Inflorescence numbers per shoot and their size vary between seasons and may, within a season, be affected by pruning systems, bud position along a cane and the size of the cane. A grapevine inflorescence typically has a main rachis and a tendril, which may or may not have flowers (an outer arm). The aim of this study was to identify the effect of these factors during inflorescence primordia (IP) initiation on the resulting number of inflorescences per shoot and their architecture. Methods and Results: Two-cane, four-cane and spur-pruned Sauvignon Blanc vines were used to investigate changes in inflorescence number, distribution and architecture over two growing seasons. The pruning system had no effect on the inflorescence number per shoot (fruitfulness), inflorescence architecture or distribution at a given cane node number. There were differences in inflorescence number and structure between the seasons, likely associated with air temperatures during primordia initiation. A warmer initiation period was associated with an increase in the occurrence of flowers on the outer arm and lower positions of the basal inflorescences (shoot bud position). An increase in cane cross-sectional area correlated to an increase in fruitfulness and an increase in the average occurrence of an outer arm with flowers along a cane. Conclusions: Inflorescence number, the position of the basal inflorescence on the developing shoot and the development of the outer arm are affected by the bud position of the shoot along a cane, the cross-sectional area of the cane and the season. Our results suggest that initiation of IP may occur at the same time for all bud positions along a shoot, so long as they are free from inhibiting factors. Significance of the Study: Cane selection can be used to modify inflorescence number and architecture and thus the potential yield of grapevines

Can a change in vineyard practice mitigate warming due to climate change?

Predicted warming resulting from climate change is expected to advance the phenology of grapevines. As a consequence, where traditional vineyard methods are used, fruit will ripen earlier in the growing season and potentially under warmer conditions. This in turn may alter the flavour and aroma profiles of wines grown in many of the traditional winegrowing regions of the world. Modified vineyard management practices may be used to negate the effects of changes in development time from warming as indicated from techniques that delay the onset of véraison (e.g., delaying pruning time, reducing the leaf area to fruit weight ratio, and/or using plant growth regulators after fruit set). These practices may counteract a small (+0.5°C) increase in average daily temperature enabling current grape cultivars to continue to be grown in traditional regions. However, these modified practices may be insufficient to reverse the advance in phenology resulting from a temperature rise of 2.0°C

Data requirements for identifying macroscopic water stress parameters: A study on grapevines

We have tested the inverse modeling approach to derive macroscopic water stress parameters (MWSP) using different types of information, such as soil water content, pressure head, and transpiration rate. This testing was performed by numerical experiments considering a multilayered soil growing grapevines under three different irrigation regimes and two contrasted water stress scenarios. The results indicate that measurements of the soil water content alone do not contain enough information to estimate MWSP. Nonuniqueness is likely to occur, and the MWSP estimates may contain large uncertainties. However, the incorporation of only transpiration measurements into the objective function does allow the deriving of accurate MWSP. This contrast is mainly due to the difference of sensitivity to the MWSP, which is much higher for the transpiration than for the soil water content. Results obtained using only soil water pressure head measurements are similar to or poorer than those obtained using transpiration data. Moreover, visual inspection of response surfaces of the objective function suggests that the incorporation of further information in addition to transpiration into the objective function is not of great value for the identification of MWSP. Uncertainties for the MWSP estimated using the three types of information combined are in most cases only 1.3 times smaller than when transpiration measurements alone are incorporated into the objective function. Beyond the specific results obtained for the estimation of MWSP we find that the parameters estimates and their associated uncertainties are strongly dependent upon the type, quantity, and quality of the information included into the objective function. Hence inverse modeling may provide a means to design better experiments

Pre-budburst temperature influences the inner and outer arm morphology, phenology, flower number, fruitset, TSS accumulation and variability of Vitis vinifera L. Sauvignon Blanc bunches

Background and Aims: Inflorescence morphology, flower formation and subsequent fruit development of grapevines are influenced by genetic, environmental and cultural practices. While the effect of temperature on inflorescence primordia number per bud is documented, its effect during dormancy and budburst (BB) on floral development is less clear. In our study, winter dormant buds were passively heated for different of time from mid-winter (July) to BB (October). Methods and Results: Canes were heated, pre-budburst, for different periods using polythene tunnels. Heating during winter dormancy had no effect on the number or position of inflorescences on the shoot, or on the type of structure occurring at the outer arm position of the inflorescence. Heating buds for either July or August to BB advanced the date of BB and the start date of flowering by 12-14 and 14 days respectively compared with the no-heat Control treatment. There was a significant (P<0.05) negative correlation between the mean temperature 12 days pre-BB and flower number per shoot. The time between 50% flowering and the fruit soluble solids content reaching 14°Brix was not influenced by winter heating or the date of flowering; however, the difference in this time interval between the inner and outer arm components increased as shoot node number increased. Conclusions: Flower number per inflorescence had the greatest influence on percentage fruit set. The date of flowering of the outer arm was later at higher inflorescence positions on the shoot and later than that of the inner arm. Likewise, the outer arms of bunches higher up the shoot took longer to go from flowering to a fruit soluble solids content of 14°Brix. Significance of the study: Much of the within-vine variability in berry composition at harvest can be attributed to the position of bunches on the shoot and the presence of the outer arm. The outer arm on apical bunches took significantly longer to progress from flowering to a fruit soluble solids content of 14°Brix, suggesting that removal would significantly reduce within-vine fruit variability.This work is part of the NewZealand Grape andWine Research program, a joint investment by New Zealand Winegrowers and The New Zealand Institute for Plant & Food Research Limited (PFR). The study was funded by The Foundation for Research Science and Technology (Designer Grapevines – CO6X0707), PFR and a Lincoln University research writing scholarship

The influence of root restriction, soil texture and lateral growth on vine balance and ripening of Pinot noir

Understanding vine balance is essential to develop tools that can potentially assist growers enhance yield without compromising the quality of Pinot noir production. The aim of this research was to examine the effect of pot volume and soil texture on Pinot noir vine balance and berry composition through manipulating the environment in which roots grow (competing sinks). A potted vine model system was set up over two growing seasons where the competing sinks (roots) of Pinot noir were manipulated via pot volume (7.5 L and 4 L pot) and soil texture (0% gravel or 50% gravel) in a controlled environment glasshouse. The influence of laterals as competing source and sinks in combination with root volume was also evaluated. This study showed that increasing pot volume increased the competing sink size of roots in the presence of laterals. However, neither soil texture nor pot volume alterations led to an increase in yield. Moreover, in 50% gravel soil and 4 L volume pots, an increase in vegetative growth occurred, primarily attributed to lateral growth. In the absence of laterals, the competing sinks of roots attained a larger proportion of carbohydrates and therefore responded as a vigorous sink in response to increased pot volume (7.5 L) and potting mix volume (0% gravel). This study demonstrate that vine balance is likely to be modified according to planting density, soil volume and texture, suggesting that in the long term these management aspects may provide tools to adjust the yield-quality seesaw

Characterizing retained dormant shoot attributes to support automated cane pruning on Vitis Vinifera L. cv. Sauvignon Blanc

Background and Aims: The shortage of skilled pruners portends automation as an alternative. To train an Artificial Intelligence (AI) system in cane pruning, the attributes of grapevine dormant shoots were characterised. Methods and Results: Eight attributes of dormant shoots, diameter, length, vertical and horizontal distance, node number, internode length, origin and position relative to bottom fruiting wire, were measured prior to and after pruning. Vine canopies were modified according to a 5 [total node numbers on canes: 10, 20, 30, 40, 50] × 3 [total node numbers on spurs: 1, 2, 3] factorial design. Compared to non-retained dormant shoots, retained dormant shoots were thicker (9.2 ± 0.07 mm), longer (104.7 ± 0.93 cm), close to the vine trunk (11.4 ± 0.65 cm) and below the bottom fruiting wire (83.2 ± 0.54 cm). Spurs had the shortest horizontal (9.8 ± 0.93 cm) and vertical (77.8 ± 0.7 cm) distance, originating from the vine head, base nodes and first nodes of old canes and old spurs. Modifying the vine canopy via increased node numbers had a significant effect on all retained dormant shoot attributes (P < 0.05) except on the position relative to the bottom fruiting wire. Conclusions: Cane pruning in commercial vineyards is consistent and follows rules based on viticulture knowledge. Retained, non-retained dormant shoots, canes and spurs exhibit distinct attributes useful in quantifying, assessing and modelling cane pruning. Significance of the Study: Data and knowledge from the research are currently being used in modelling and training AI cane-pruning algorithms

The application of high-resolution atmospheric modelling to weather and climate variability in vineyard regions

Grapevines are highly sensitive to environmental conditions, with variability in weather and climate (particularly temperature) having a significant influence on wine quality, quantity and style. Improved knowledge of spatial and temporal variations in climate and their impact on grapevine response allows better decisionmaking to help maintain a sustainable wine industry in the context of medium to long term climate change. This paper describes recent research into the application of mesoscale weather and climate models that aims to improve our understanding of climate variability at high spatial (1 km and less) and temporal (hourly) resolution within vineyard regions of varying terrain complexity. The Weather Research and Forecasting (WRF) model has been used to simulate the weather and climate in the complex terrain of the Marlborough region of New Zealand. The performance of the WRF model in reproducing the temperature variability across vineyard regions is assessed through comparison with automatic weather stations. Coupling the atmospheric model with bioclimatic indices and phenological models (e.g. Huglin, cool nights, Grapevine Flowering Véraison model) also provides useful insights into grapevine response to spatial variability of climate during the growing season, as well as assessment of spatial variability in the optimal climate conditions for specific grape varieties