Identifying individual nutrient deficiencies of grapevine leaves using hyperspectral imaging

The efficiency of a vineyard management system is directly related to the effective management of nutritional disorders, which significantly downgrades vine growth, crop yield and wine quality. To detect nutritional disorders, we successfully extracted a wide range of features using hyperspectral (HS) images to identify healthy and individual nutrient deficiencies of grapevine leaves. Features such as mean reflectance, mean first derivative reflectance, variation index, mean spectral ratio, normalised difference vegetation index (NDVI) and standard deviation (SD) were employed at various stages in the ultraviolet (UV), visible (VIS) and near-infrared (N.I.R.) regions for our experiment. Leaves were examined visually in the laboratory and grouped as either healthy (i.e. control) or unhealthy. Then, the features of the leaves were extracted from these two groups. In a second experiment, features of individual nutrient-deficient leaves (e.g., N, K and Mg) were also analysed and compared with those of control leaves. Furthermore, a customised support vector machine (SVM) was used to demonstrate that these features can be utilised with a high degree of effectiveness to identify unhealthy samples and not only to distinguish from control and nutrient deficient but also to identify individual nutrient defects. Therefore, the proposed work corroborated that HS imaging has excellent potential to analyse features based on healthiness and individual nutrient deficiencies of grapevine leaves

Elevated root-zone temperature hastens vegetative and reproductive development in Shiraz grapevines

Background and Aims: Springtime root-zone warming activates mobilisation of the root carbohydrate reserves, a critical source of carbon for early canopy and reproductive development in grapevines following winter dormancy. Seasonal variability in soil temperature during spring may result in inconsistent vegetative growth and fruitset with consequences for berry growth and ripening. Methods and Results: We monitored flowering and berry ripening in Shiraz grapevines (Vitis viniferaL.) grown in large temperature-controlled pots. The vines were exposed to a cool, ambient and warm root-zone temperature from budburst to fruitset. Root starch mobilisation after budburst was linearly correlated to the cumulative heat units received by the soil. A warm root-zone temperature also hastened leaf expansion, net positive carbon assimilation, onset of flowering and fruit set, berry enlargement and the onset of veraison. At harvest, berry pH and nitrogen concentration as well as fresh and dry mass were higher for the vines exposed to a warm root-zone while berry acidity was lower. Conclusions: Warm soil temperature in spring stimulated the mobilisation of carbohydrates in the roots and accelerated shoot and reproductive development, resulting in larger berries with lower acidity. Significance of the Study: Because root-zone temperature is an environmental driver of berry size and composition, models predicting yield and berry composition can be fine-tuned to incorporate this critical parameter

Computer vision and machine learning for viticulture technology

This paper gives two contributions to the state-of-the-art for viticulture technology research. First, we present a comprehensive review of computer vision, image processing, and machine learning techniques in viticulture. We summarize the latest developments in vision systems and techniques with examples from various representative studies, including, harvest yield estimation, vineyard management and monitoring, grape disease detection, quality evaluation, and grape phenology. We focus on how computer vision and machine learning techniques can be integrated into current vineyard management and vinification processes to achieve industry relevant outcomes. The second component of the paper presents the new GrapeCS-ML database which consists of images of grape varieties at different stages of development together with the corresponding ground truth data (e.g., pH and Brix) obtained from chemical analysis. One of the objectives of this database is to motivate computer vision and machine learning researchers to develop practical solutions for deployment in smart vineyards. We illustrate the usefulness of the database for a color-based berry detection application for white and red cultivars and give baseline comparisons using various machine learning approaches and color spaces. This paper concludes by highlighting future challenges that need to be addressed prior to successful implementation of this technology in the viticulture industry.</p

Geographical Origin Has a Greater Impact on Grape Berry Fungal Community than Grape Variety and Maturation State

We used barcoded sequencing to analyze the eukaryotic population in the grape berries at different ripening states in four Australian vineyards. Furthermore, we used an innovative compositional data analysis for assessing the diversity of microbiome communities. The novelty was the introduction of log-ratio balances between the detected genera. Altogether, our results suggest that fungal communities were more impacted by the geographical origin of the Australian vineyards than grape variety and harvest time. Even if the most abundant genera were Aureobasidium and Mycosphaerella, they were ubiquitous to all samples and were not discriminative. In fact, the balances and the fungal community structure seemed to be greatly affected by changes of the genera Penicillium, Colletotrichum, Aspergillus, Rhodotorula, and Botrytis. These results were not evident from the comparison of relative abundance based on OTU counts alone, remarking the importance of the balance analysis for microbiome studies

Late-season Shiraz berry dehydration that alters composition and sensory traits of wine

Late-season berry dehydration (LSD) is a common occurrence in Shiraz grapes, particularly those grown in hot climates. LSD results in significant yield reductions; however, the effects on wine composition and sensory characteristics are not well-documented. Wines made of 100% nonshriveled clusters (control) were related to red fruit flavors by the sensory panel, whereas wines made of 80% shriveled clusters (S-VCT) were perceived as more alcoholic and associated with dark fruit and dead/stewed fruit characters. The latter wines also resulted in higher concentrations of massoia lactone and γ-nonalactone, compounds known to contribute to prune and stewed-fruit aromas. Wines made of shriveled grapes were also characterized by an increase in C6-alcohols and a decrease in esters, whereas wine terpenoids were altered compound-specific. An increase in orange pigments and wine chemical age in S-VCT wines indicated faster oxidative aging compared to the control. LSD appeared to alter final wine composition directly but also appeared to influence yeast metabolism, potentially due to an alteration of the composition of lipids in the grape juice. This study emphasized the relevance of sorting shriveled and nonshriveled berries for final wine chemical composition and wine style

Differential accumulation of potassium in the vegetative and reproductive organs of three grapevine cultivars

Vine nutrition and vineyard fertilizer management have long-term implications for plant performance, notably vigour, crop load and fruit composition. Grape and wine composition is intrinsically linked to vineyard management practises. Wine sensory outcomes such as flavour, colour and aroma are heavily dependent upon intrinsic grape properties including pH, which in turn is influenced by berry potassium (K) concentration. Cultivar differences in the accumulation of nutrients is evident, however, tracking the accumulation of K in the various vine tissues is crucial for understanding how this macronutrient should be monitored during the season to achieve optimum growth performance and grape quality. We studied three economically important wine grape cultivars in Australia, grown under identical conditions, to determine how K accumulation differs between the cultivars, between the vegetative and reproductive organs and between two node positions on the shoot. The samples were collected at flowering and veraison and analysed for K by inductively coupled plasma atomic emission spectroscopy (ICP-AES). K concentrations ([K]) increased or decreased between these two phenological stages depending on cultivar, organ and node position. [K] in the berry and flower were not correlated with [K] in the leaf blade, petiole, or bunch stem. The differential accumulation of K in various organs points towards complex partitioning and mobilisation patterns, and this will have implications for berry pH and acidity at harvest. The differential accumulation of K between cultivars suggests that cultivar specific reference standards are required

Changes in volatile composition and sensory attributes of wines during alcohol content reduction

A desirable sensory profile is a major consumer driver for wine acceptability and should be considered during the production of reduced-alcohol wines. Although various viticultural practices and microbiological approaches show promising results, separation technologies such as membrane filtration, in particular reverse osmosis and evaporative perstraction, in addition to vacuum distillation, represent the most common commercial methods used to produce reduced-alcohol wine. However, ethanol removal from wine can result in a significant loss of volatile compounds such as esters (ethyl octanoate, ethyl acetate, isoamyl acetate) that contribute positively to the overall perceived aroma. These losses can potentially reduce the acceptability of the wine to consumers and decrease their willingness to purchase wines that have had their alcohol level reduced. The change in aroma as a result of the ethanol removal processes is influenced by a number of factors: the type of alcohol reduction process; the chemical-physical properties (volatility, hydrophobicity, steric hindrance) of the aroma compounds; the retention properties of the wine non-volatile matrix; and the ethanol level. This review identifies and summarises possible deleterious influences of the dealcoholisation process and describes best practice strategies to maintain the original wine composition

Regional discrimination of Australian Shiraz wine volatome by two-dimensional gas chromatography coupled to time-of-flight mass spectrometry

Shiraz wine volatomes from two Australian geographical indications (GIs), that is, Orange and Riverina, were compared using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry. Shiraz wines were made in triplicate from grapes harvested at two harvest dates from six vineyards in the two GIs. A total of 133 compounds showed a significant trend between wines from the cooler Orange GI and warmer Riverina. Compounds associated with wines from the cooler climate were grape-derived volatiles, such as monoterpenes, sesquiterpenes, green leaf volatiles, and some norisoprenoids. Fermentation-derived compounds, such as esters and S-containing compounds, showed no specific trend related to grape origin. In addition, wines could be also clearly separated according to the harvest date, irrespective of the climate, with C6 compounds, higher alcohol acetates, and other esters contributing utmost to the differentiation of samples, whereas terpenoids and norisoprenoids did not have an influence. This study demonstrated the plasticity of wine volatome related to grape origin and also the maturity level (harvest date), irrespective of climate

J. Agric. Food Chem.

This work reports the quantitation and sensory characterization of 1,4-cineole in red wine for the first time. A headspace–solid-phase microextraction–gas chromatography–mass spectrometry (HS–SPME–GC–MS) method was developed to quantitate 1,4-cineole and 1,8-cineole in 104 commercial Australian red wines. 1,4-Cineole was detected in all of the wines analyzed, with concentrations ranging from 0.023 to 1.6 μg/L. An important varietal effect was observed, with concentrations of 1,4-cineole in Cabernet Sauvignon wines (mean of 0.6 ± 0.3 μg/L) significantly higher than in Shiraz (0.07 ± 0.04 μg/L) and Pinot Noir (0.2 ± 0.2 μg/L) wines. Regional variations of both cineole isomer concentrations have been measured between wines originating from different Australian regions. Sensory studies demonstrated that the addition of 0.54 μg/L 1,4-cineole in a Cabernet Sauvignon wine, to produce a final concentration of 0.63 μg/L, was perceived significantly by a sensory panel (p < 0.05). Descriptive analyses revealed that 1,4-cineole and 1,8-cineole may contribute to the hay, dried herbs, and blackcurrant aromas reported in Australian Cabernet Sauvignon wines and may be potential markers of regional typicality of these wines

Impact of Fluorescent Lighting on Oxidation of Model Wine Solutions Containing Organic Acids and Iron

Previous studies have provided evidence that light exposure can increase oxygen consumption in wine and that the photodegradation of iron­(III) tartrate could contribute to this process. In the present study, model wine solutions containing iron­(III) and various organic acids, either alone or combined, were stored in sealed clear glass wine bottles and exposed to light from fluorescent lamps. Dissolved oxygen was monitored, and afterward the organic acid degradation products were determined and the capacity of the solutions to bind sulfur dioxide, the main wine preservative, was assessed. In the dark controls, little or no dissolved oxygen was consumed and the organic acids were stable. In the irradiated solutions, dissolved oxygen was consumed at a rate that was dependent on the specific organic acid present, and the latter were oxidized to various carbonyl compounds. For the solutions containing tartaric acid, malic acid, and/or citric acid, irradiation increased their sulfur dioxide-binding capacity