Correction to “Effectiveness of Different Bud Forcing Treatments to Achieve Double Cropping in Cabernet Sauvignon Grapevines Grown in South Australia”

An epidemic of grapevine leafroll disease (GLD), caused by grapevine leafroll-associated virus 3 (GLRaV-3), was monitored over an 11-year period in Nuriootpa, South Australia. Inoculum originated from infected budwood, and initial GLD incidence at the time of transplanting in 1986 was 23.1%. Infected vines were planted in a random spatial pattern. Change in disease incidence was not observed until 8 years after planting, when disease incidence increased to 27.9%. Disease incidence increased to 51.9% by 1996. Disease progress and rate curves (dy/dt versus time) indicated that the logistic (R2 = 96.2) and Gompertz (R2 = 96.3) growth models would best describe disease progress. However, the logistic model, which has a simpler data transformation with fewer model assumptions, was chosen for the purpose of comparing this epidemic (South Australia) with a GLRaV-3 epidemic in Cabernet Sauvignon grapevines in New Zealand. The logistic rate of GLD spread with respect to time was 0.35 logit/year in South Australia and was nearly three times faster (1.19 logits/year) for GLRaV-3 spread in New Zealand. Ordinary runs analyses indicated that the arrangement of infected vines within rows in South Australia was random up to 8 years after transplanting but subsequently became highly aggregated. Thus, GLD-infected plants are contributing to new infections (i.e., there is evidence for plant-to-plant spread), and a biotic vector with a steep dispersal gradient from each point source is likely to be involved.

Background and Aims Global warming is driving increased heat accumulation and longer growing seasons, making it feasible to ripen two crops in a single season, even in temperate regions where grapevines experience winter dormancy. Methods and Results A 2‐year study on Cabernet Sauvignon in South Australia evaluated vine responses to a “double cropping” technique aimed at producing two consecutive crops (primary [P] and forced [F]) within the same season. The forced crop was achieved by breaking bud dormancy through severe trimming at the groat‐size berry stage; retaining four, six or eight main leaves on the shoot (F4, F6, F8); and concurrently removing any developing laterals. These treatments were compared to an unforced control (C). Vine performance was assessed through phenology, vegetative growth, yield components, vine balance indices and grape composition at harvest. In the 2022–2023 season, the response to forcing was faster (13 days) and more active (0.69 forced shoots/total shoots) than in the 2023–2024 season (19 days and 0.47 forced shoots/total shoots, respectively). Reactivity to forcing tended to decrease at F8 compared to F4 and F6. On average, the forced leaf area (LA) constituted 59.2% of the total LA. Across all F treatments, the total yield per vine was 11.6% higher than C, with the forced crop contributing 36.1% of the total yield. Forced shoot bunches were consistently smaller and looser than those on the P shoots and harvest of the second crop occurred 56–60 days later. Forcing significantly delayed the ripening of the primary crop compared to the control, yet fruit in F treatments reached a relatively high TSS (23.7–24.1°Brix) while maintaining higher TA and lower pH, indicating a desynchronisation of sugar and acid ripening. Seasonal variation strongly influenced anthocyanin and phenolic accumulation: in 2022–23, levels were highest in F treatments, even compared to the control; in 2023–2024, they were comparatively low. Since LA/Y remained adequate, it is hypothesised that late‐season microclimate conditions are likely the primary factor in berry pigmentation outcomes. Conclusions and Significance of the Study Overall, this technique shows promise for improving vineyard profitability by increasing total yield and offering opportunities for the diversification of wine styles. Work is underway to develop mechanised approaches for broader adoption.

The wine industry is important to Australia's economy. With the advances in remote sensing there has been increasing interest in its potential application for vineyard varietal, condition and health mapping. CASI (Compact Airborne Spectrographic Imager) data was obtained over a vineyard in the Barossa Valley, South Australia in an attempt to discriminate between the grape cultivars (Vitis vinifera), Cabernet Sauvignon and Shiraz. Statistical analysis of sample spectra from the two varieties in the CASI imagery showed that the significant differences in the visible region. Maximum likelihood classification was employed to map the two grape varieties present on the site. Classification was performed using 12 visible and near infrared CASI bands and repeated using a spectral subset of seven bands shown to be most significant in separating the varieties. Discrimination between Cabernet Sauvignon and Shiraz was successful with 91.5% of vine rows correctly classified. Spectral subsetting did not improve classification and led to under classification of vine pixels.

The increasing prevalence of the grapevine trunk diseases Eutypa and Botryosphaeria dieback has been attributed, in part, to abiotic stresses imposed on vineyards as production intensifies worldwide. The aim of this study was to evaluate the influence of water deficit irrigation practices on the infection of pruning wounds by Eutypa lata and Diplodia seriata and the subsequent rate of colonization. Two vineyard trials were conducted over two consecutive seasons in South Australia, one in the Riverland with 'Cabernet Sauvignon' with four irrigation treatments (100, 50, 25, and 12.5% of the standard irrigation program) and another in the Barossa Valley with 'Shiraz' on six rootstocks and own roots, either irrigated or not irrigated. According to leaf water potential assessments, vines with reduced irrigation were generally in water deficit and therefore subjected to stress. On the whole, incidence of wound infection and distance of colonization were similar between irrigation treatments for both pathogens, except in the Riverland, where E. lata colonized canes to a greater extent in well-watered vines than those in water deficit. Only vines on rootstock 'Ramsey' in the Barossa Valley had greater extent of colonization by E. lata in the nonirrigated vines. There was no correlation between internal staining and colonization, with both pathogens recovered to nearly 20 cm ahead of the staining. Water deficit did not increase the susceptibility of grapevine pruning wounds to infection or colonization of the subtending tissue by E. lata and D. seriata. In fact, there was evidence of lower susceptibility to colonization by E. lata in vines subjected to severe water deficit.

In the context of water management in agriculture, irrigation scheduling is critically important as it optimises water application to crops and can also target specific production goals. However, there is no consensus on the ideal irrigation scheduling strategy regarding crop water use efficiency (WUEc). In a premium Cabernet Sauvignon vineyard in Coonawarra, South Australia, over three growing seasons, irrigation scheduling strategies based on experience or historical knowledge (‘GROW’ treatment) were compared to data-driven strategies including crop evapotranspiration, and plant and soil water status thresholds to evaluate their effects on leaf- and vine-level WUEs. A final treatment, GROW + , that doubled the GROW level of irrigation was also evaluated in the third season. The WUE metrics were determined at the leaf, vine, and fruit scales as intrinsic WUE (WUEi), crop WUE (WUEc), and carbon isotope ratio (δ13C), respectively. Furthermore, the irrigation strategies were evaluated in the background of two contrasting soil types: Terra Rossa (light clay, well-drained) and Rendzina (heavier clay, poorly drained). Seasonal soil and vine water status, leaf gas exchange, and light interception were measured, and yield components and pruning weights were obtained following harvest. The amount of seasonal irrigation water based on the data-driven strategies was up to 65% lower across both soil types compared with the GROW or GROW + approaches. WUEi and δ13C were largely similar between treatments. However, for vines grown on Terra Rossa soil, little to no yield penalty was observed when data-driven irrigation scheduling was applied, in addition to increased WUEc values of up to 41%. It can be concluded that irrigation scheduling decisions based on data were superior to the conventional irrigation scheduling method on account of reducing irrigation water volume and increasing WUE, particularly in Terra Rossa soils.

Accurate assessment of a crop’s water requirement is essential for optimising irrigation scheduling and increasing the sustainability of water use. The crop coefficient (Kc) is a dimensionless factor that converts reference evapotranspiration (ET0) into actual crop evapotranspiration (ETc) and is widely used for irrigation scheduling. The Kc reflects canopy cover, phenology, and crop type/variety, but is difficult to measure directly in heterogeneous perennial systems, such as vineyards. Remote sensing (RS) products, especially open-source satellite imagery, offer a cost-effective solution at moderate spatial and temporal scales, although their application in vineyards has been relatively limited due to the large pixel size (~100 m2) relative to vine canopy size (~2 m2). This study aimed to improve grapevine Kc predictions using vegetation indices derived from harmonised Sentinel-2 imagery in combination with spectral unmixing, with ground data obtained from canopy light interception measurements in three winegrape cultivars (Shiraz, Cabernet Sauvignon, and Chardonnay) in the Barossa and Eden Valleys, South Australia. A linear spectral mixture analysis approach was taken, which required estimation of vine canopy cover through beta regression models to improve the accuracy of vegetation indices that were used to build the Kc prediction models. Unmixing improved the prediction of seasonal Kc values in Shiraz (R2 of 0.625, RMSE = 0.078, MAE = 0.063), Cabernet Sauvignon (R2 = 0.686, RMSE = 0.072, MAE = 0.055) and Chardonnay (R2 = 0.814, RMSE = 0.075, MAE = 0.059) compared to unmixed pixels. Furthermore, unmixing improved predictions during the early and late canopy growth stages when pixel variability was greater. Our findings demonstrate that integrating open-source satellite data with machine learning models and spectral unmixing can accurately reproduce the temporal dynamics of Kc values in vineyards. This approach was also shown to be transferable across cultivars and regions, providing a practical tool for crop monitoring and irrigation management in support of sustainable viticulture.

The evolving spatial and temporal knowledge about vineyard performance through the use of remote sensing offers new perspectives for vine water status studies. This paper describes the application of aerial thermal imaging to evaluate vine water status to improve irrigation scheduling decisions, water use efficiency, and overall winegrape quality in the Coonawarra viticultural region of South Australia. Airborne infrared images were acquired during the 2016 and 2017 growing seasons in the region of Coonawarra, South Australia. Several thermal indices of crop water status (CWSI, Ig, (Tc-Ta)) were calculated that correlated with conventional soil and vine water status measures (Ψpd, Ψs, gs). CWSI and Ig could discriminate between the two cultivars used in this study, Cabernet Sauvignon (CAS) and Shiraz (SHI), as did the conventional water stress measures. The relationship between conventional vine water status measures appeared stronger with CWSI in the warmer and drier season (2016) compared to the cooler and wetter season (2017), where Ig and (Tc-Ta) showed stronger correlations. The study identified CWSI, Ig and (Tc-Ta) to be reliable indicators of vine water status under a variety of environmental conditions. This is the first study to report on high resolution vine water status at a regional scale in Australia using a combination of remote and direct sensing methods. This methodology is promising for aerial surveillance of vine water status across multiple blocks and cultivars to inform irrigation scheduling.

The incidence of grapevine bunchstem necrosis (BSN) in cv. Cabernet Sauvignon was assessed in three South Australian regions during three years. The percentage of bunches affected varied widely—from nil to 26%‐between years and regions. At the site with most BSN, high incidence was related to lower temperatures during 20 days before flowering and not to low temperatures during flowering. Also, incidence was higher when rain fell during veraison. Minimally pruned vines had significantly less BSN than spur‐pruned vines in each of the three test years.

Sclerotinia sclerotiorum was recovered from rotting grapevine shoots (Vitis vinifera) cv. Cabernet Sauvignon in a vineyard in South Australia in October 2000. The fungus was also detected in October and November 2001 in a further 14 vineyards in the cooler grape growing areas of South Australia, affecting Cabernet Sauvignon, Shiraz, Pinot Noir, Riesling, Verdelho and Sauvignon Blanc. In severely infected vineyards, crop loss occurred from the death of shoots and cordons.

This paper reports on the development of a rapid and simple method for red wine authenticity confirmation during transport and processing; namely, a wine "fingerprinting" system. When wine is transported between two sites, a sample is taken and a mid-infrared (MIR) spectrum is obtained. One hundred sixty-one (n = 161) samples of three main red wine varieties grown in Australia, Shiraz, Cabernet Sauvignon, and Merlot, were collected from six commercial wineries across Australia and scanned in transmission on two MIR spectrophotometers located at The Hardy Wine Company's main site at Reynella, South Australia (Foss WineScan FT 120) (926-5012 cm-1). A similarity index (SI) method was used as a tool to classify wine samples on the basis of their spectral data. The results showed that high rates of classification were obtained when wine samples scanned in different instruments were analyzed. The SI has been proven to provide an acceptable measurement for authentication of red wine integrity during transportation. In five of the six winery data sets, the SI correctly classified 98% of the wines. It was also observed that less than 1% of wines were misclassified between the different wineries investigated. Further studies are needed in order to test the applicability of the SI in a commercial situation and to evaluate its potential as a rapid quality control tool for routine use to authenticate wine samples during transport.

Pseudomonas syringae was recorded on grapes (Vitis vinifera) for the first time in South Australia in November 2000. The bacterium was recovered from angular leaf lesions collected from affected Verdelho vines from a vineyard in the cooler grape growing regions of South Australia. In November 2001, further infections were confirmed on Merlot, Cabernet Sauvignon, Viognier, Sauvignon Blanc and Chardonnay from three of the cooler winegrowing areas close to Adelaide. No crop loss has been recorded.

Crop water status and irrigation requirements are of great importance to the horticultural industry due to changing climatic conditions leading to high evaporative demands, drought and water scarcity in semi-arid and arid regions worldwide. Irrigation scheduling strategies based on evapotranspiration (ET), such as regulated deficit irrigation, requires the estimation of seasonal crop coefficients (kc). The ET-driven irrigation decisions for grapevines rely on the sampling of several kc values from each irrigation zone. Here, we present an unmanned aerial vehicle (UAV)-based technique to estimate kc at the single vine level in order to capture the spatial variability of water requirements in a commercial vineyard located in South Australia. A UAV carrying a multispectral sensor is used to extract the spectral, as well as the structural, information of Cabernet Sauvignon grapevines. The spectral and structural information, acquired at the various phenological stages of the vine through two seasons, is used to model kc using univariate (simple linear), multivariate (generalised linear and additive) and machine learning (convolution neural network and random forest) model frameworks. The structural information (e.g., canopy top view area) had the strongest correlation with kc throughout the season (p ≤ 0.001; Pearson R = 0.56), while the spectral indices (e.g., normalised indices) turned less-sensitive post véraison—the onset of ripening in grapes. Combining structural and spectral information improved the model’s performance. Among the investigated predictive models, the random forest predicted kc with the highest accuracy (R2: 0.675, root mean square error: 0.062, and mean absolute error: 0.047). This UAV-based approach improves the precision of irrigation by capturing the spatial variability of kc within a vineyard. Combined with an energy balance model, the water needs of a vineyard can be computed on a weekly or sub-weekly basis for precision irrigation. The UAV-based characterisation of kc can further enhance the water management and irrigation zoning by matching the infrastructure with the spatial variability of the irrigation demand.

The field performance of selections of Cabernet Sauvignon was evaluated from 1958 to 1988, with the aim of improving yields by visual selection of healthy, vigorous, productive clones from aged, productive vineyards within a district, and by systematic comparison of these clones with candidates from other districts, States, and countries. There were 9 clonal comparison trials, with reference clones provided by results from preceding trials. High yield (5-10 kg/vine) had little effect on juice composition, and performances of high-yielding selections in a range of areas were identified. These clones (SA 125, BVRC 17, G9V3, LC 10 and CW 44) have been established in Registered Source Areas and their cuttings distributed to the grapegrowing industry through the South Australian Vine Improvement Program. Single-vine plots with 10-20 replicates were suggested for more rigorous statistical separation of clones. It is desirable to test clones in the districts where they were selected and where they are to be planted.

Transcriptional expression of Stilbene synthase genes are regulated developmentally and differentially in response to powdery mildew in Norton and Cabernet Sauvignon grapevine

Girdling is a traditional horticultural practice applied at fruit set or other phenological stages, and is used mostly as a vine management. In grapevines, it is used primarily for table grapes to improve berry weight, sugar content, color, and to promote early harvest. The objective of this study was to evaluate the effect of trunk girdling applied at veraison, in ‘Cabernet Sauvignon’ wine grapes (Vitis vinifera L.), on agronomical and physiological parameters during vine development from the onset of ripening (veraison) to harvest, and additionally to quantify the effect of girdling on primary and secondary metabolism. Girdling was applied 146 days after pruning (dap) at veraison, when berry sampling for metabolomics and agronomical evaluations commenced, with a further three sampling dates until harvest, at 156 dap (30% maturation, 10 days after girdling-dag), 181 dap (70% maturation, 35 dag), and 223 dap (commercial harvest, 77 dag). Skin/pulp and seed tissues were extracted separately and metabolomics was performed using one-dimensional proton nuclear magnetic resonance (1D 1H NMR) spectroscopy and high performance liquid chromatography (HPLC-DAD). At harvest, girdling significantly increased stomatal conductance (gs) in vines, decreased glutamine concentrations, and increased anthocyanin and flavonol concentrations in the skin/pulp tissues of grape berries. Berry weight was reduced by 27% from 181 dap to harvest, and was significantly higher in grapes from girdled vines at 181 dap. Sugars, organic acids, and other amino acids in skin/pulp or seeds were not significantly different, possibly due to extra-fascicular phloem vessels transporting metabolites from leaves to the roots. Using a metabolomics approach, differences between skin/pulp and seeds tissues were meaningful, and a greater number of secondary metabolites in skin/pulp was affected by girdling than in seeds. Girdling is a simple technique that could easily be applied commercially on vine management to improve berry color and other phenolics in ‘Cabernet Sauvignon’ grapes.