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

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 i.e. 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

Reduced grapevine canopy size post-flowering via mechanical trimming alters ripening and yield of 'Pinot noir'

The degree and time of canopy trimming can alter phenology, rates of increase or decrease in berry components during grape ripening, and may influence yield and its components. The objective of this study was to investigate the extent to which reducing canopy size, by mechanical trimming post-flowering, changed Vitis vinifera L. 'Pinot noir' fruit yield and composition. Vines were mechanically trimmed to three different canopy heights at fruitset: 1000 mm (100 % canopy height), 600 mm (60 % canopy height relative to the control treatment) and 300 mm (30 % canopy height relative to the control treatment). Total soluble solids concentration and content, titratable acidity, pH and fresh berry mass were measured throughout ripening, and yield and leaf area were measured at harvest.Reduced canopy size via trimming to 30 and 60 % of the control treatment height slowed total soluble solids accumulation and in some cases increased titratable acidity and increased pH. The total soluble solids-titratable acidity ratio was therefore reduced throughout ripening by these trimming treatments relative to the full canopy height. Trimming to reduce canopy size had two effects on the source-sink ratio; it reduced the source (canopy) but increased fruit yield, an important sink. Therefore, the time of trimming is an important management consideration because it can delay and slow ripening due to reduced source leaves but could potentially accentuate the delay via increasing yield (sink). This technique may represent a way to offset the acceleration of phenology and grape ripening that has been observed to occur as a result of warmer seasons

Developing perennial fruit crop models in APSIM Next Generation using grapevine as an example

A new model for grapevines (Vitis vinifera) is the first perennial fruit crop model using the Agricultural Production System sIMulator (APSIM) Next Generation framework. Modules for phenology, light interception, carbohydrate allocation, yield formation and berry composition were adapted or added into APSIM Next Generation to represent the nature of fruit-bearing vines. The simulated grapevine phenological cycle starts with the dormancy phase triggered by a critical photoperiod in autumn, and then goes through the subsequent phenophases sequentially and finally returns to dormancy for a new cycle. The canopy microclimate module within APSIM Next Generation was extended to allow for row crop light interception. The carbohydrate arbitrator was enhanced to consider both sink strength and sink priority to reflect carbohydrate reserve as a concurrent competing sink. Weather conditions and source-sink ratio at critical developmental stages were used to determine potential grapevine yield components, e.g. bunch number, berry number and berry fresh weight. The model was calibrated and tested extensively using four detailed data sets. The model captured the variations in the timing of measured budburst, flowering and véraison over 15 seasons across New Zealand for five different varieties. The calculated seasonal dynamics of light interception by the row and alley were consistent with field observations. The model also reproduced the dynamics of dry matter and carbohydrate reserve of different organs, and the wide variation in yield components caused by seasonal weather conditions and pruning regimes. The modelling framework developed in this work can also be used for other perennial fruit crops

Potential of a multiparametric optical sensor for determining in situ the maturity components of red and white vitis vinifera wine grapes

A non-destructive fluorescence-based technique for evaluating Vitis vinifera L. grape maturity using a portable sensor (Multiplex ®) is presented. It provides indices of anthocyanins and chlorophyll in Cabernet Sauvignon, Merlot and Sangiovese red grapes and of flavonols and chlorophyll in Vermentino white grapes. The good exponential relationship between the anthocyanin index and the actual anthocyanin content determined by wet chemistry was used to estimate grape anthocyanins from in field sensor data during ripening. Marked differences were found in the kinetics and the amount of anthocyanins between cultivars and between seasons. A sensor-driven mapping of the anthocyanin content in the grapes, expressed as g/kg fresh weight, was performed on a 7-ha vineyard planted with Sangiovese. In the Vermentino, the flavonol index was favorably correlated to the actual content of berry skin flavonols determined by means of HPLC analysis of skin extracts. It was used to make a non-destructive estimate of the evolution in the flavonol concentration in grape berry samplings. The chlorophyll index was inversely correlated in linear manner to the total soluble solids (°Brix): it could, therefore, be used as a new index of technological maturity. The fluorescence sensor (Multiplex) possesses a high potential for representing an important innovative tool for controlling grape maturity in precision viticulture

The effect of pre-budbreak cane girdling on the physical and phenological development of the inner and outer arm in Vitis vinifera L. 'Sauvignon blanc' inflorescence structures

The development of inflorescence primordia (IP) into floral bearing structures is influenced by many environmental and genetic factors. We hypothesise that carbohydrate (CHO) availability at budbreak (BB) has a strong influence on IP development, especially during the initial stages of shoot growth when pre-formed IP emerge from dormant buds and may be dependent on reserve CHOs for further branching and development. Carbohydrate availability to developing grapevine buds (Vitis vinifera L. 'Sauvignon blanc') was manipulated by girdling canes two weeks before BB. Dates of flowering, flower number, berry number and grape berry soluble solids (SS) were measured for the inner and outer arm bunch components of basal and apical bunches separately. Restricting pre-BB CHOs resulted in the abortion of some pre-formed inflorescences and reduced branching of the inflorescences that did develop. In general, berry SS were greatest for the basal inner arm, followed by those of the apical bunch inner arm, then those of the basal bunch outer arm, then lastly by those of the apical bunch outer arm. However, this was influenced by the relative berry numbers between the inner and outer arm. Bunches with more similar berry numbers on the inner and outer arms had more synchronous flowering and uniform SS, where the differences in SS were largely a reflection of the timing of flowering of the various inflorescence components and may be an important source of variation in SS within a vine at harvest

Influence of cane diameter on gross profit

Mark Eltom, from New Zealand’s Lincoln University, Department of Wine, Food & Molecular Biosciences; together with Chris S. Winefield, and Mike C.T. Trought have been studying how cane diameter and structure influence the gross return to growers. This report is based on their paper “Effects of shoot girdling and/or periodic leaf removal on inflorescence primordia initiation and development in Vitis vinifera L. cv. Sauvignon Blanc”, portions of which have previously been published in the Australian Journal of Grape and Wine Research and Practical Winery & Vineyard

Application of high-resolution climate measurement and modelling to the adaptation of New Zealand vineyard regions to climate variability

Initial results are presented of research into the relationship between climate variability and viticulture in New Zealand vineyards. Atmospheric modelling and analytical tools are being developed to improve adaptation of viticultural practices and grape varieties to current and future climate. The research involves application of advanced local and regional scale weather and climate models, and their integration with grapevine phenological and crop models. The key aims are to improve adaptation of grape varieties to fine scale spatial variations of climate, and reduce the impact of climate variation and risk factors such as frost, cool spells and high temperatures. Improved optimization of wine-grape production through better knowledge of climate at high resolution within vineyard regions will contribute to the future sustainability of high quality wine production. An enhanced network of automatic weather stations (AWS) has been installed in New Zealand’s premier vineyard region (Marlborough) and the Weather Research and Forecasting (WRF) model has been set up to run twice daily at 1 km resolution through the growing season. Model performance has been assessed using AWS data and the model output is being used to derive high-resolution maps and graphs of bioclimatic indices for the vineyard region. Initial assessment of model performance suggested that WRF had a cold bias, but this was found to be due to errors in the default surface characteristics. Spatial patterns of predicted air temperature and bioclimatic indices appear to accurately represent the significant spatial variability caused by the complex terrain of the Marlborough region. An automated web page is being developed to provide wine-producers with daily up-dates of observed and modelled information for the vineyard region. Latest results of this research will be provided along with a review of the 2013-14 growing season, using data from both the climate station network and WRF model output

Underpinning Terroir with Data: Integrating Vineyard Performance Metrics with Soil and Climate Data to Better Understand Within-Region Variation in Marlborough, New Zealand

Background and Aims. Previous work in Australia has demonstrated the value of data-driven approaches to terroir analysis but, like other terroir research, focussed predominantly on the natural resources (soils, topography, and climate) on which winegrowing depends. In only very few cases have metrics of production performance also been considered. In this study, focussed on the Marlborough region of New Zealand, we integrated data pertaining to vineyard performance with biophysical data (soils and climate) describing the conditions under which grapes are grown to give a more holistic indication of regional-scale variation in the terroir of the Marlborough production system. Methods and Results. Digital map layers describing variation in climate, soil properties, and the yield and harvest date of Sauvignon Blanc (Vitis vinifera L.) were assembled and analysed for similarity in their patterns of spatial variation over six vintages (2014–2019) using k-means clustering. The results suggest that the Marlborough region has a characteristically variable Sauvignon Blanc production with crop phenology and harvest date strongly influenced by variation in temperature, and yield variation impacted by soil properties. Spatial variation in seasonal rainfall did not appear to impact on vineyard performance. Importantly, the Wairau and Awatere valleys which, hitherto, have been considered together as parts of a single Marlborough region, are shown to be distinct. Conclusions. This analysis is strongly suggestive of the Marlborough terroir being variable at the within-region scale. It also lends weight to the idea that estimates of vineyard performance in some parts of the region may be used to predict performance in others. Significance of the Study. The results have potentially important implications for the management of both vineyard operations and winery logistics, for wine marketing and for whole-of-industry planning around expansion or contraction. The methods used are free of any bias introduced to many previous studies of terroir zoning through adherence to historical or geopolitical boundaries, expert opinion of wines, and other heuristics

Understanding flowering of Sauvignon blanc in the Marlborough region, New Zealand, using high-resolution weather forecasting and the grapevine flowering véraison model

High-resolution weather forecasting and phenological models can be combined to better understand spatial and temporal variations in the phenology of grapevine varieties. The objective of this study was to compare predictions of the time of flowering of Sauvignon blanc in the Marlborough region, New Zealand, using the Grapevine Flowering Véraison (GFV) model using temperature input data from: 1) traditional Automated Weather Stations (AWS); and 2) the Weather Research and Forecasting (WRF) model. Phenology was monitored at ten sites in 2013-14, and seven of the same sites in 2014-15, where there were corresponding AWS on site. The day of 50% flowering was determined at these sites and compared with the predicted dates simulated using the combination of the GFV model with temperature data from the AWS data and WRF models. For most sites in the central Wairau and Awatere valleys, the GFV predictions based on both temperature data sources were in agreement with observations However, there were some spatial trends in the GFV prediction bias with both temperature data sources (AWS and WRF); for example, in 2013-14 coastal and the most inland sites the predicted flowering dates were earlier than those observed. The WRF model produced differences between observations and predictions of similar magnitude to those of the AWS data and therefore provides suitable temperature input data input for phenological modelling. The agreement between AWS and WRF indicates that the observed biases are likely from the phenological model predictions, not the temperature data sources. The WRF model can therefore be used instead of AWS to generate regional maps of flowering date at 1-km resolution.This combined modelling approach can be used to integrate new phenological models, for other phenological stages, other varieties and existing or new regions, to anticipate sub-regional differences in grapevine development