Cassandra Collins

VitiCanopy: A Free Computer App to Estimate Canopy Vigor and Porosity for Grapevine

Leaf area index (LAI) and plant area index (PAI) are common and important biophysical parameters used to estimate agronomical variables such as canopy growth, light interception and water requirements of plants and trees. LAI can be either measured directly using destructive methods or indirectly using dedicated and expensive instrumentation, both of which require a high level of know-how to operate equipment, handle data and interpret results. Recently, a novel smartphone and tablet PC application, VitiCanopy, has been developed by a group of researchers from the University of Adelaide and the University of Melbourne, to estimate grapevine canopy size (LAI and PAI), canopy porosity, canopy cover and clumping index. VitiCanopy uses the front in-built camera and GPS capabilities of smartphones and tablet PCs to automatically implement image analysis algorithms on upward-looking digital images of canopies and calculates relevant canopy architecture parameters. Results from the use of VitiCanopy on grapevines correlated well with traditional methods to measure/estimate LAI and PAI. Like other indirect methods, VitiCanopy does not distinguish between leaf and non-leaf material but it was demonstrated that the non-leaf material could be extracted from the results, if needed, to increase accuracy. VitiCanopy is an accurate, user-friendly and free alternative to current techniques used by scientists and viticultural practitioners to assess the dynamics of LAI, PAI and canopy architecture in vineyards, and has the potential to be adapted for use on other plants.

Effect of Water Stress on the Reproductive Performance of Shiraz (Vitis vinifera L.) Grafted to Rootstocks

An experiment was conducted in the Barossa Valley, South Australia, to examine the effect of rootstocks on reproductive performance of Shiraz (Vitis vinifera L.) under water stress. Vines were grown on own roots or grafted to 110R, 1103P, 99R, Ramsey, Schwarzmann, or 140Ru. Vines either were unirrigated or irrigation was applied at 56 to 128 mm/ha across three seasons. Water stress (Ψpd < 0.8 MPa) was apparent in the unirrigated vines from veraison onward. The absence of irrigation strongly influenced vine growth and performance. Pruning weight, cane weight, and cane number were all reduced as a consequence of zero irrigation. Yields were reduced in unirrigated treatments due to a reduction in cluster number, cluster weight, and berry weight rather than fruit set or berry number. Unirrigated Ramsey was the only rootstock able to maintain yield comparable with irrigated rootstocks. Unirrigated own roots performed well in the first season but not in the second and third seasons when water stress had a negative effect on yield. Millerandage, coulure, and seedless berry numbers were the main reproductive parameters found to have a negative impact on yield and both own-rooted and grafted vines were as susceptible to these parameters. Season had a greater influence than either rootstock type or irrigation. These findings have significant implications for regions facing future drought and declining water supplies.

Evaluation of Sensory Thresholds and Perception of Sodium Chloride in Grape Juice and Wine

Poor water quality and lack of rainfall can lead to higher salt loads in vineyard soil and the production of wine with sodium chloride (NaCl) concentrations that may affect wine quality or exceed regulatory limits. Here, study 1 aimed to determine NaCl sensory thresholds in grape juice and wine so that better harvest and processing decisions could be made regarding salt-affected fruit. A whole-mouth gustatory method was used to determine detection and recognition thresholds of NaCl in water, red and white juices, and wines. The NaCl sensory thresholds were often within legal boundaries; thus, a significant proportion of wine consumers may detect salt in wines at concentrations below the legal NaCl limits. The detection and recognition thresholds of NaCl in grape juice and wine increased with panelist age. Study 2 investigated how NaCl affects wine sensory properties. Sensory evaluation using a trained descriptive analysis panel (n = 9) and chemical and elemental analyses were conducted on four Chardonnay wines made from separate vineyards where the fruit was perceived to contain varying degrees of saltiness and results were compared to Chardonnay wine samples spiked with 0.5 or 1 g/L NaCl. Wines made from fruit grown on salt-affected vines and wines spiked with NaCl had similar sensory characteristics. Salty and soapy attributes were correlated and associated with higher Na and Cl concentrations. Fruit expression was associated with wines containing less Na and Cl. When determining acceptable salt concentrations in juice and wines, winemakers need to consider sensory impacts, legal requirements, and who conducts the sensory assessment.

Modified Method for Producing Grapevine Plants in Controlled Environments

The rapid production of small fruiting grapevines under controlled environmental conditions is an invaluable tool for viticulture research, particularly studies involving flowering, fruit set, and berry development. The objective of this study was to determine an optimal growth strategy to produce experimental grapevine plants with adequate and consistent reproductive performance and to fully describe the approach to allow other researchers to produce consistent material from controlled environments year-round. Three different nutrient regimes were used to grow Shiraz (Vitis vinifera L.) plants from one-year-old cuttings in perlite:vermiculite and under controlled environmental conditions. Percentage fruit set, Coulure index, and Millerandage index were determined. The growth strategy produced a fruit set percentage >50% (in Shiraz) and optimum leaf elemental concentrations. These modifications to the Mullins and Rajasekaran (1981) method, including automated irrigation, improve the assessment and manipulation of grapevine reproductive performance and vine physiology in controlled conditions and highlight the importance of knowing how growth medium contributes to the nutrient status and hence growth of experimental grapevine plants.

A Concise Review on Multi-Omics Data Integration for Terroir Analysis in Vitis vinifera

Vitis vinifera (grapevine) is one of the most important fruit crops, both for fresh consumption and wine and spirit production. The term terroir is frequently used in viticulture and the wine industry to relate wine sensory attributes to its geographic origin. Although, it can be cultivated in a wide range of environments, differences in growing conditions have a significant impact on fruit traits that ultimately affect wine quality. Understanding how fruit quality and yield are controlled at a molecular level in grapevine in response to environmental cues has been a major driver of research. Advances in the area of genomics, epigenomics, transcriptomics, proteomics and metabolomics, have significantly increased our knowledge on the abiotic regulation of yield and quality in many crop species, including V. vinifera. The integrated analysis of multiple ‘omics’ can give us the opportunity to better understand how plants modulate their response to different environments. However, ‘omics’ technologies provide a large amount of biological data and its interpretation is not always straightforward, especially when different ‘omic’ results are combined. Here we examine the current strategies used to integrate multi-omics, and how these have been used in V. vinifera. In addition, we also discuss the importance of including epigenomics data when integrating omics data as epigenetic mechanisms could play a major role as an intermediary between the environment and the genome.

What Does Sustainability Mean? Knowledge Gleaned From Applying Mixed Methods Research to Wine Grape Growing

We present outcomes from a mixed methods research project in agricultural sciences. An atypical methodology for sciences was developed as the only way to avoid embedded assumptions commonly seen in sustainability investigations. Eighty-three upper echelon participants from the wine grape industry participated in 14 focus groups in five countries: Australia, Chile, New Zealand, South Africa, and the United States. Quantitative measures were compared with results from qualitatively coded participant utterances using two content analysis software tools: Leximancer and NVivo. This article presents the strategies and method applied in this investigation to define sustainability. A consensual sustainability definition prior to the establishment of assessment systems is essential. The model developed seems to be viable for similar sustainability investigations of individual organizations.

Relationships between grape and wine sensory attributes and compositional measures of cv. Shiraz

Relationships among sensory attributes, compositional measures, and wine quality of Shiraz grapes and wines were evaluated for two seasons, 2009 to 2010 and 2010 to 2011. The sensory profiles of berries and wines were evaluated by descriptive analysis and wine quality was assessed by an expert panel. In this study, berry sensory attributes alone were better predictors of wine sensory and compositional variables than the combination of berry sensory and compositional variables. Partial least squares regression analysis and Pearson’s correlation revealed a negative relationship between seed bitterness and wine savory spice flavor in both seasons. In 2011, pulp detachment from the skin correlated with wine sensory attributes such as rim color, fresh dark berry flavor, savory spice flavor, and wine quality score. Correlations among wine sensory attributes, wine pigmented polymers, and wine total tannins were identified in both seasons. These findings are important for grapegrowers and winemakers as they identify berry sensory attributes that may assist as objective measures in predicting final wine style and quality.

Rootstock Effects on Primary Bud Necrosis, Bud Fertility, and Carbohydrate Storage in Shiraz

Shiraz grapevines (Vitis vinifera L.) grafted to three different hybrid (American Vitis) rootstocks at two sites were used to evaluate the effect of rootstock on primary bud necrosis (PBN), fruitfulness, and carbohydrate storage. Buds were dissected during winter dormancy and assessed for the number of inflorescence primordia and incidence of primary bud necrosis. Trunks, canes, and roots were sampled at dormancy for carbohydrate concentration. A water deficit treatment was also applied at one of the two locations. Fruitfulness and yield were affected by water deficit. Rootstock type influenced the incidence of primary bud necrosis, fruitfulness, and carbohydrate concentration at both sites.

Salinity Negatively Affects Pollen Tube Growth and Fruit Set in Grapevines and Is Not Mitigated by Silicon

Soil salinity impairs viticultural production by reducing vegetative growth and yield parameters such as bud fruitfulness, bunch number per cane, bunch weight, and berry weight. However, the effects of salinity on flower fertility, berry set, and berry development, and the resulting impacts on fruit yield are not well understood. The ability of silicon (Si) to enhance salt tolerance and yield performance has been well documented for some crops. Here, we investigated whether Si could improve grapevine reproductive performance, particularly under saline conditions. One-year-old Shiraz (Vitis vinifera L.) cuttings were grown in controlled conditions and treated with salt (35 mM NaCl) and/or Si (1.5 mM K2SiO3) from budburst to veraison. Salt stress reduced fruit set by increasing flower abscission and interrupting normal berry development, which resulted in more live green ovaries and seedless berries per bunch. In vitro and in vivo studies confirmed that poor berry development due to impaired fertilization was correlated with poor pollen tube growth in the style; pollen viability and stigma receptivity were not affected by salinity. Significantly more sodium (Na+) and chloride (Cl−) were present in leaves and flowers of plants in the salt treatments compared to control plants. Silicon did not prevent the accumulation of Na+ and Cl− in reproductive organs or ameliorate the deleterious effects of salinity on reproductive capacity. However, Si-treated vines showed better instantaneous water use efficiency than control vines. This study suggests that fertilization is sensitive to salt accumulation and that salt exposure should be avoided to minimize negative effects of salinity on fruit yield.

Global DNA Methylation Patterns Can Play a Role in Defining Terroir in Grapevine (Vitis vinifera cv. Shiraz)

Understanding how grapevines perceive and adapt to different environments will provide us with an insight into how to better manage crop quality. Mounting evidence suggests that epigenetic mechanisms are a key interface between the environment and the genotype that ultimately affect the plant’s phenotype. Moreover, it is now widely accepted that epigenetic mechanisms are a source of useful variability during crop varietal selection that could affect crop performance. While the contribution of DNA methylation to plant performance has been extensively studied in other major crops, very little work has been done in grapevine. To study the genetic and epigenetic diversity across 22 vineyards planted with the cultivar Shiraz in six wine sub-regions of the Barossa, South Australia. Methylation sensitive amplified polymorphisms (MSAPs) were used to obtain global patterns of DNA methylation. The observed epigenetic profiles showed a high level of differentiation that grouped vineyards by their area of provenance despite the low genetic differentiation between vineyards and sub-regions. Pairwise epigenetic distances between vineyards indicate that the main contributor (23–24%) to the detected variability is associated to the distribution of the vineyards on the N–S axis. Analysis of the methylation profiles of vineyards pruned with the same system increased the positive correlation observed between geographic distance and epigenetic distance suggesting that pruning system affects inter-vineyard epigenetic differentiation. Finally, methylation sensitive genotyping by sequencing identified 3,598 differentially methylated genes in grapevine leaves that were assigned to 1,144 unique gene ontology terms of which 8.6% were associated with response to environmental stimulus. Our results suggest that DNA methylation differences between vineyards and sub-regions within The Barossa are influenced both by the geographic location and, to a lesser extent, by pruning system. Finally, we discuss how epigenetic variability can be used as a tool to understand and potentially modulate terroir in grapevine.