Commercial Vineyard Research Articles

Effects of biodynamic preparations 500 and 501 on vine and berry physiology, pedology and the soil microbiome

In the pursuit of increasing sustainability, climate change resiliency and independence of synthetic pesticides in agriculture, the interest of consumers and producers in organic and biodynamic farming has been steadily increasing in recent decennia. This is, in particular, the case for the vitivinicultural industry in Europe, where more and more producers are converting from organic to biodynamic farming. However, clear scientific evidence showing that biodynamic farming improves vine physiology, vine stress resilience, soil quality related parameters and berry or wine quality is still lacking, despite the growing number of research studies on this issue. To investigate whether biodynamic farming methods have an impact on vine physiology, berry quality and the environment, a five-year experiment was set up in 2016 in a commercial vineyard in Switzerland. In this trial, the two main biodynamic preparations 500 and 501 were applied and compared to an organic control. Vine and berry physiology (net photosynthesis, vigour, sugar, organic acids, berry weight, yield) were assessed from 2016 to 2020. Soil physical properties (soil bulk density, water holding capacity, soil structural stability, macropore volume) were analysed from 2017-2020, and, soil fungal communities were analysed by DNA-sequencing in the last year of the experiment (2020). None of the parameters related to vine and berry physiology showed significant differences throughout the duration of the experiments, except photosynthesis, which was higher when biodynamic preparations were applied at one time point. Similarly, the soil’s physical properties were not influenced by the application of the two biodynamic preparations in all years. Regarding the soil microbiome, the preparations 500 and 501 neither led to significant differences in fungal diversity nor seemed to impact the soil fungal communities. The present study confirms previous findings of different research teams that did not observe significant differences between organic and biodynamic farming methods in terms of observed soil and vine parameters.

A crop water stress index based internet of things decision support system for precision irrigation of wine grape

The goal of irrigation for wine grape grown in arid or semiarid regions is to sustain vine survival and to optimize berry attributes for quality wine production. Precision irrigation of wine grape is impeded by the lack of a smart, decision support system (DSS) to remotely monitor vine water status. The objectives of this study were to: develop and field test an Internet of Things (IoT) DSS system for precision irrigation of wine grape. The IoT system was comprised of a suite of in situ sensors used to monitor real-time weather conditions, grapevine canopy temperature, soil moisture, and irrigation amount. Sensor data were collected and stored on a field deployed data logger that calculated a daily thermal Crop Water Stress Index (CWSI) for grapevine using a neural network model with real-time sensor data model inputs. The data logger also hosted, via a cellular modem, webpages showing a running, 12-day history of daily CWSI, fraction of available soil moisture (fASW), irrigation amount, and other sensor data. The webpages were accessible to vineyard managers via cell phone or computer. The CWSI based IoT DDS system was installed at two small acreage, commercial estate vineyards in southwestern Idaho USA over four growing seasons. At each vineyard site, the DSS was used daily by the vineyard irrigation manager to schedule irrigation events. Neither vineyard manager used any other quantitative vine water status monitoring tool for irrigation management decisions. The midday leaf water potential (LWP) of grapevines was routinely measured by research project personnel. Data collected over the study period at each vineyard showed a significant (p < 0.001) correlation with LWP and fASW, providing evidence that, under the conditions of this study, the daily CWSI based IoT provided automated, remote monitoring of vine water status. Both vineyard managers reported daily use of the DSS for irrigation scheduling decisions. Over the four-year study, each vineyard manager was able to maintain consistent seasonal average CWSI daily values and irrigation application amounts, despite yearly differences in climatic conditions. The results of this study demonstrate that a CWSI based IoT DSS can be used for precision irrigation of wine grape in a commercial vineyard under semiarid growing conditions. The CWSI based IoT DSS used a unique combination of neural network modeling, edge computing, and IoT for real-time vine water stress monitoring for precision irrigation.

Can Satellite Remote Sensing Assist in the Characterization of Yeasts Related to Biogeographical Origin?

Biogeography is a key concept associated with microbial terroir, which is responsible for the differentiation and uniqueness of wines. One of the factors influencing this microbial terroir is the vegetation, which in turn is influenced by climate, soil, and cultural practices. Remote sensing instruments can provide useful information about vegetation. This study analyses the relationship between NDVI, calculated using Sentinel-2 and Landsat-8 satellite images of different veraison dates, and microbial data obtained in 2015 from 14 commercial (organic and conventional) vineyards belonging to four Designations of Origin (DOs) from Galicia (northwest Spain). Microbial populations in grapes and musts were identified using PCR techniques and confirmed by sequencing. Statistical analyses were made using PCA, CCA, TB-PLS, and correlation analyses. This study confirms that the NDVI is positively correlated with the diversity of yeasts, both in grapes' surface and must samples. Moreover, the results of this study show: (i) Sentinel-2 images, as well as Landsat-8 images, can establish differences in NDVI related to yeast terroir in grapes and musts, as it is the most relevant DO factor, (ii) Sentinel-2 NDVI and yeast biogeography are moderately to strongly correlated, (iii) Sentinel-2 achieved a better delimitation of the DOs than Landsat-8 and can establish more accurate differences in NDVI-yeast terroir correlations, and (iv) a higher NDVI was associated with the yeast biogeographical patterns of the DOs with higher species richness (S) consisting of weakly fermenting yeasts (Hanseniaspora uvarum, Pichia spp., Starmerella bacillaris, and Zygosaccharomyces spp). However, NDVI values did not correlate well with biogeographic patterns of yeasts previously studied at frequency level (proportion or percentage of each species) in each particular DO. This study suggests that satellite imagery has the potential to be a valuable tool for wine quality management and a decision-making instrument for DO regulators and winegrowers.

Tolerance of muscadine grape to 2,4-D choline postemergence-directed

AbstractField studies were conducted in commercial muscadine vineyards in western North Carolina in 2018 and eastern North Carolina in 2019, 2020, and 2021 to determine tolerance of younger (&lt; 9 yr) and older (≥ 9 yr) bearing muscadine grapevines to 2,4-D directed beneath the crop postemergence (POST). Treatments included 2,4-D choline at 0, 0.53, 1.06, 1.60, and 2.13 kg ae ha−1 applied as a single treatment in May or June (spring) at immediate pre-bloom, and sequential treatments at 0.53 followed by (fb) 0.53, 1.06 fb 1.06, 1.6 fb 1.6, or 2.13 fb 2.13 kg ha−1. The first sequential treatment was applied in spring fb another application of the same amount in July (summer) at pre-veraison. No differences in injury on muscadine grapevines were observed from 2,4-D treatments. Differences among treatments were not observed for yield of younger vines. However, for older vines, a difference due to 2,4-D rate was observed in 2018, when yield was higher when 2,4-D was applied at 1.6 kg ha−1 compared with nontreated grapevines, and when 2,4-D was applied at 0.53 and 2.13 kg ha−1. A rate-by-timing interaction was observed in 2019 when yield was lower from 0.53 kg ha−1 2,4-D summer application compared with all other summer treatments but similar to the nontreated. However, no biological pattern was observed from either of these differences. No differences among treatments were observed for fruit pH, titratable acidity, or soluble solid content of either younger or older vines.

Viticulture adaptation to global warming: Modelling gas exchange, water status and leaf temperature to probe for practices manipulating water supply, canopy reflectance and radiation load

Associated with climate change, the frequency, duration, and intensity of heatwaves are increasing in most of the key wine regions worldwide. Depending on timing, intensity, and duration, heatwaves can impact grapevine yield and berry composition, with implications for wine quality. To overcome these negative effects, two types of mitigation practices have been proposed (i) to enhance transpiration and (ii) to reduce the radiation load on the canopy. Here we use a biophysical model to quantify the impact of these practices on canopy gas exchange, vine water status, and leaf temperature (Tl). Model validation was performed in a commercial vineyard. Modelled Tl from 14 to 43 °C, and transpiration, from 0.1 to 5.4 mm d−1, aligned around the identity line with measurements in field-grown vines; the RMSD was 2.6 ºC for temperature and 0.96 mm day−1 for transpiration. Trellis system and row orientation modulate Tl. A sprawling single wire trellis with an EW orientation maintained the canopy around 1ºC cooler than a Vertical Shoot Positioned canopy with NS for the same range of total fraction of soil available water (TFAW). Although irrigation before a heatwave is a recommended practice, maximum transpiration can be sustained even when TFAW is reduced, limiting the heat dampening effect of irrigation. Alternatively, canopy cooling can be achieved through Kaolin application, the installation of shade cloth placement, or canopy trimming. Shade cloth produced a greater cooling than Kaolin in all the simulated scenarios; however, Tl differences between them varied. Trimming reduced Tl from 2 ºC to almost 8 ºC compared to its non-trimmed counterpart. Our analysis presents new insights to design heat wave mitigation strategies and supports agronomically meaningful definitions of heat waves that include not only temperature, but also wind, VPD, and radiation load as these factors influence crop physiology under heat stress.

Occurrence of Nine Grapevine Viruses in Commercial Vineyards of Mendoza, Argentina

Grapevine is a widely grown fruit crop that is seriously affected by different viruses, reducing grape yield and quality, as well as threatening profitability. Vineyard disease management requires accurate identification of viral infections. This study aimed to survey the presence of ten grapevine viruses in four geographic sites in the Mendoza province of Argentina. Two hundred twenty-three composite cane samples from 1060 plants of six cultivars were collected from 26 blocks distributed across 11 vineyards. The cane samples were screened by RT-PCR for the following viruses: grapevine leafroll-associated viruses 1-4 (GLRaV 1, 2, 3, and 4), grapevine fanleaf virus (GFLV), grapevine fleck virus (GFkV), grapevine virus A (GVA) and B (GVB), grapevine rupestris stem pitting associated virus (GRSPaV), and arabis mosaic virus (ArMV). The results showed an uneven occurrence of viruses through the sampled regions, with GRSPaV being prevalent (71.1%), followed by GFLV (28.9%), GFkV (20.6%), and GLRaV-2 (14.7%). GVB was not detected. This study revealed a moderate prevalence of viruses associated with economically impactful diseases in the vineyards surveyed.

High-resolution geomatics tools: Sustainably managing commercial vineyards to address the UN SDGs

The UN 2030 Agenda for Sustainable Development provides a shared blueprint for peace and prosperity for people and the planet. Consisting of 17 Sustainable Development Goals (SDGs), it calls for action in a global partnership. Geographical Information Systems (GIS) have been proposed as an advanced tool for managing variability in commercial vineyards, gaining a high-resolution spatial perspective on crop performance distribution and its underpinning reasons. Recent evolution of open- source GIS software democratized access and provided an easy and affordable way for vineyard managers to combine a «big picture» with zooming in at each individual plant, in representing diverse datasets and performing complex calculations in geographic representation. Newly available sets of climate, soil, water, ecosystem and biodiversity data are contributing to the capacity to integrate conservation management in commercial vineyards, making geomatic technology an essential tool to measure and manage sustainable development indicators. In our study, we demonstrate the use of geomatic technologies in the management of a commercial vineyard by combining traditional management blocks with segmentation of geophysical and ecosystem characteristics and using those tools to design efficient drainage and measure non-crop areas for nature conservation. We propose those technologies to assess contributions for SDGs 12, 13, and 15.

Assessing grapevine water status using Sentinel-2 images

Grapevine water status strongly impacts vine yield and berry quality, hence the importance of a cost- and time-effective methodology to estimate it in commercial vineyards. A two-year experiment was carried out in a rainfed commercial vineyard (cv. ‘Vermentino’ grafted on ‘1103P’) to test the ability of vegetation indices (VIs) derived from Sentinel-2 (S2) multispectral imagery in estimating the stem water potential (Ψstem). The S2 VIs calculated including NIR and SWIR bands (NDMI, MSI and NMSI), performed better (R2 values of 0.66, 0.66 and 0.59, respectively) than those calculated using the bands in the VIS-NIR region (R2 values 0.47, 0.58 and 0.58 for NDVI, GNDVI and NDWI, respectively). The slope between B8a and B11 bands was also significantly affected by grapevine water status. The different weather conditions occurred during the two experimental years also allowed to observe as the S2 VIs performed better in estimating Ψstem under prolonged drought conditions. Moreover, S2 VIs were not able to detect differences in grapevine water status during the onset of water stress condition

Effect of Irrigation with Treated Municipal Wastewater on Vitis vinifera L. cvs. Cabernet Sauvignon and Sauvignon blanc in Commercial Vineyards in the Coastal Region of South Africa - Vegetative Growth, Yield and Juice Characteristics

Effect of Irrigation with Treated Municipal Wastewater on Vitis vinifera L. cvs. Cabernet Sauvignon and Sauvignon blanc in Commercial Vineyards in the Coastal Region of South Africa - Vegetative Growth, Yield and Juice Characteristics

Dinâmica temporal de Plasmopara viticola em função do aumento da carga de gemas em 'Sauvignon Blanc'

Abstract The objective of this work was to evaluate the effect of increasing bud load per plant on epidemiological variables of downy mildew on 'Sauvignon Blanc'. The study was carried out in a commercial vineyard in a high-altitude region of the municipality of São Joaquim, in the state of Santa Catarina, Brazil, during the 2016/2017 and 2017/2018 vintages. The treatments consisted of four bud loads: 15, 30, 50, and 75 per vine. The maximum incidence, maximum severity, beginning of symptom appearance, time to reach maximum disease incidence and severity, area under the incidence and severity disease progress curve were determined. Increasing bud load over 50 per vine results in higher incidence and severity of downy mildew (Plasmopara viticola) in 'Sauvignon Blanc' leaves but does not influence the time to reach maximum disease incidence and severity. Increasing bud load over 50 per vine results in an increase in the area under the disease incidence and severity progress curve for downy mildew in 'Sauvignon Blanc' leaves. To adopt over 50 buds per vine treatment, it is necessary additional disease control measures, with an emphasis on integrated management to control downy mildew.

Assessment of the qualitative and quantitative characteristics of the grapes of grapevine cultivar Fokiano (Vitis vinifera L.) in Ikaria Island, under vineyard conditions

This study aimed at assessing the phenolic potential of indigenous Greek red grapevine cultivar Fokiano under different cultivation systems and altitudes, during the cultivation season 2019-2020, which could explore different approaches yielding better results in the same viticultural area, as is Ikaria Island. The samples of the present study were collected from productive (commercial) vineyards in the island of Ikaria, in the region of the North Aegean Sea. Samples of grapes were collected from 7 different vineyards at the northern part of Ikaria with different characteristics: (i) difference in the altitude of the vineyards and (ii) difference in the cultivation system (conventional or organic). The vineyards in question are located at an altitude of 200 m, 400 m, 600 m and 800 m. The samples were collected during the dates of harvest, which were determined according to the technological maturation of the grapes in combination with the biodynamic calendar. In all samples, the mechanical analyses of the grapes and berries took place and the characters of the must as well as the qualitative characters of the berries (must, skins, seeds) were studied. Total soluble solids of the must were calculated using a refractometer, the active acidity (pH) using a pH meter and the total acidity using a sodium hydroxide solution (NaOH). The mechanical analyses that were performed involved the weight of thirty (30) berries, the weight of the grape and the length and width of the berries and the grapes of each sample. The content of grape's skin in total anthocyanins, total phenolics, condensed tannins, total ortho-diphenols, total flavonoids, total flavanols, total flavonols and flavones and their antioxidant capacity with the use of FRAP and DPPH methods were determined using a spectrophotometer. The most important acids found in grapes were identified using High-Performance Liquid Chromatography (HPLC). The measurements in the grape seeds were made on the same compounds as the skins, except for total anthocyanins. The results of the present study showed that the altitude does not seem to have a significant effect on most of the qualitative and quantitative characters of the cultivar in Ikaria, however, in future studies, other factors that affect the qualitative characters of the grapes need to be taken into consideration and further evaluated. The microclimate of the highest altitude (800 m) had a positive effect regarding total phenolics, anthocyanins, tannins, flavonols, o-diphenol content and the antioxidant capacity of the skins according to FRAP method, but with opposite results in the case of the seeds. At the same time, it should be noted that no accurate conclusion can be drawn regarding the cultivation system (conventional or organic), since between the two pairs of conventional and organic vineyards (samples from conventional and organic vineyards at an altitude of 200 m - samples from conventional and organic vineyard at an altitude of 600 m), the measurements exhibit a variation in their results. The antioxidant capacity that was determined in the samples of Fokiano is also remarkable, when also compared with other indigenous red grapevine cultivars. In view of climate change, the exploitation of indigenous varieties under different soil and climatic conditions or even in the same viticultural region, like the one of the current experiment (different cultivation system, different altitude in the island of Ikaria) could unlock and highlight the full potential of such local varieties, depending on the final style of the wine produced.

Managing Arbuscular Mycorrhizal Fungi in Arid Columbia Basin Vineyards of the Pacific Northwest United States

<h3>Abstract</h3> <h3>Background and goals</h3> Arbuscular mycorrhizal fungi (AMF) are root symbionts that help grapevines acquire nutrients from soil. Growers in many regions, including the Columbia River basin of Oregon and Washington, lack information needed to best manage AMF. Such lacking information includes understanding whether natural AMF populations are sufficient to ensure healthy colonization in new plantings, and what factors influence AMF in established plantings. <h3>Methods and key findings</h3> AMF colonization of grapevine fine roots was determined in 32 commercial vineyards and in a vineyard that was heavily infested by the northern root-knot nematode (NRKN, <i>Meloidogyne hapla</i>). Root colonization by AMF was as extensive in young vines (one- to two-years-old) as in older vines (&gt;15-years-old) examined in the survey, and was high throughout the season in the single vineyard trial. AMF colonization was greater overall in red wine grape cultivars than in white wine grape cultivars. AMF colonization correlated negatively with soil nitrate and leaf nitrogen (N) concentrations across vineyards, while arbuscules in roots correlated negatively with NRKN populations in soil. Both AMF and arbuscules in roots correlated negatively with NRKN populations per unit of fine root length at the beginning and end of the growing season in the heavily infested vineyard. <h3>Conclusions and significance</h3> Results suggest that AMF populations in soils of the Columbia River basin are ample to ensure high levels of grapevine root colonization, so inoculation is likely not needed when planting or replanting vineyards in the region. AMF colonization was reduced by high N and high populations of NRKN in soil.

Effect of irrigation management on the relationship between stomatal conductance and stem water potential on cv. Cabernet Sauvignon

Water relations in vineyards have been largely studied; giving insides regarding the way grapevine interacts with its environment according to water availability, providing us terminologies like Isohydric and Anisohydric, which have been applied to categorize cultivars and rootstocks. Recently, the use of this terminology has been subjected to discussion regarding its use as a category to describe and separate grapevine cultivars instead of using it as a continuous, where grapevines can behave more iso or anysohidric depending on the environment where they are grown. In this study, using a deficit irrigation (RDI) trial in a commercial vineyard located in Maule Valley in Central Chile, the relationship between Midday Stem Water Potential (ψx), Stomatal Conductance (gs), Soil Water Content (WC), and Vapour Pressure Deficit (VPD) on cv. Cabernet Sauvignon was studied, a grape variety that has been classified as isohydric. The trial was carried out for 3 years from 2018 to 2020 in which four RDI treatments were employed to replenish different portions of evapotranspiration (ET) from pea-size until harvest. These irrigation treatments were conceived as 100% ET, 70% ET, 50-100% ET (50% ET before veraison and 100% ET afterwards) and 35-100% ET (35% ET before veraison and 100% ET afterwards). Findings in this study show how the relationship between ψx and gs is treatment dependent; in treatments where no water deficit was imposed a weaker relationship between the variables was observed, showing a large variation between gs at similar ψx, being gs more dependent on VPD compared to the treatments with a larger deficit on its irrigation. As the deficit irrigation increased, grapevines started to shift to a smaller variation on its gs over large variations on its ψx. This result shows that irrigation management and deficit irrigation strategies impact the way plants react to water availability and leads to different behavior on its gs/ψx relationship.

Vitis vinifera Manseng noir, the sister of Tannat. Alternative variety for low alcohol wines produced in Uruguayan conditions

Vitis vinifera Tannat was introduced in Uruguay in 1870 from the Basque Pyrenees, and within several grapevines it became the variety best adapted to our viticultural conditions. Recently, through genetic analysis it was demonstrated that Manseng Noir, in addition to originate from the same region of Tannat, is the only natural sister identified within 2500 Vitis varieties surveyed [1]. Given the small commercial vineyard of this variety in France, after several years we have managed to plant in 2019 the first vineyard outside the Pyrenees in Uruguay. In 2021 and 2022 harvests, its elaboration is achieved with the aim of comparing its wine with Tannat. Results obtained show that its agronomic phenotype, as well as aspects of sanity, acidity, and color intensity are similar to Tannat, but with the particularity that grapes are of moderate ripening, 12.5% of alc., total polyphenol index was 12% lower than the control Tannat at 14% of alcohol. Interestingly, Manseng Noir shows an early smoothness in its tannins that allow to achieve lower alcohol wines, still powerful color and structure but less astringency in the mouth. Its complete genome was sequenced by Illumina technology and comparative genome analysis with Tannat was carried on. Genetic, metabolomic and sensory analyzes comparison with Tannat are discussed in this work.

NFLUENCE OF GREENHOUSE MAINTENACE TREATMENTS ON GROWTH OF SEEDLING GRAPEVINES (Vitis spp.)

Vegetative clonal propagation of scions and rootstocks represent the commercial method of grapevine production; currently, techniques such as hardwood rooting, grafting, and tissue culture are readily exploited by the nursery and grapevine industries. Seedlings of highly heterozygous grapevines are not true to type, as a result they are not utilized in the mass production of planting stock for commercial grape vineyards. However, seedling growth and quality is key for plant breeding programs initiating thousands of unique seedlings each year. To investigate treatments for their impact on diverse interspecific cold-hardy grapevines, seedlings were grown under greenhouse conditions. Four weeks after transplant, seedlings were cut back to one true node (CUT), leaf thinned (LT), or left as untreated control vines (Control). Eight weeks after treatment, plants were analyzed for total node number, periderm encompassed nodes, lateral shoot number, and total number of base stems. Control and LT vines had more periderm encompassed nodes and total nodes than CUT vines, while CUT vines had the highest number of shoots arising from the base nodes of the vine.

Concerning the Etiology of Syrah Decline: A Fresh Perspective on an Old and Complex Issue Facing the Global Grape and Wine Industry.

Syrah decline, first identified in Southern France in the 1990s, has become a major concern in the global grape and wine industry. This disease mainly affects Syrah (Shiraz) grapevines. Characteristic symptoms include the bright and uniform reddening of leaves throughout the canopy in late summer or early fall; the appearance of abnormalities on the trunk, mainly at the graft union (swelling, pits, grooves, and necrosis); and a reduction in vine vigor, yield and berry quality. Diseased vines may die a few years after disease onset. Damages to the vine are even more pronounced in cool climate regions such as Ontario (Canada), where the affected vines are subjected to very cold and prolonged winters, leading to large numbers of vine deaths. Despite the extensive efforts of the global grape research community over the past few decades, the etiology of this disease remains unclear. In this study, we conducted extensive analyses of viruses in declining Syrah vines identified in commercial vineyards in the Niagara region (Ontario, Canada) through high-throughput sequencing, PCR, RT-PCR and the profiling of genetic variants of select viruses. Multiple viruses and viral strains, as well as three viroids, were identified. However, an unequivocal causal relationship cannot be established between Syrah decline and any of these viruses, although the possibility that certain virus or genetic variants, or both in combination, may contribute to the disease cannot be excluded. Gleaning all information that is available to date, we feel that the traditional approach and an insistence on finding a single cause for such a complex disorder in a woody perennial fruit crop involving grafting will prove to be futile. We hope that this study offers new conceptual perspectives on the etiology of this economically important but enigmatic disease complex that affects the global grape and wine industry.

Bio-based and SO2-generating plastic liners to extend the shelf life of ‘Benitaka’ table grapes

This study evaluates a bio-based laser-perforated and recyclable SO2-generating liners, alone or in combination with ultra-fast SO2-generating before packaging, to extend the shelf life of ‘Benitaka’ table grapes (Vitis vinifera L.). Grape bunches were harvested from a commercial vineyard in Parana, southern Brazil, in 2020 and 2021, and packaged in clamshells organized in cardboard boxes (10 clamshells per box). Boxes were sealed with liners and were stored at 1.0 ± 1 °C and at 70–80% relative humidity. The presence of gray mold was assessed 30 d and 45 d after cold storage, and after 3 additional days at room temperature (22 ± 1 °C); bunch weight loss, stem browning, shattered berries, and bleaching were assessed. Bio-based and SO2-generating liners, in combination with ultra-fast SO2-generating pads applied before packaging ‘Benitaka’ table grapes, were effective in controlling the incidence of gray mold at 45 d of cold storage (< 0.4%) and at 3 d of room temperature (< 0.8%); this extended the shelf life of grapes, with low weight loss, fewer shattered berries, and the maintenance of stem freshness. The bio-based liner alone does not control gray mold effectively, but it has no adverse effect on the physicochemical qualities of ‘Benitaka’ grapes and is an eco-friendly packaging material. Using compostable bio-based or recyclable SO2-generating perforated plastic liners to control gray mold and other postharvest diseases may promote the near future use of sustainable materials in the food industry.

The Biocontrol Potential of Endophytic Trichoderma Fungi Isolated from Hungarian Grapevines, Part II, Grapevine Stimulation.

In the first part of this two-piece publication, the isolation, identification and in vitro characterization of ten endophytic Trichoderma isolates were reported. Here we report the ability of two different mixes of some of these isolates (Trichoderma simmonsii, Trichoderma orientale and Trichoderma gamsii as well as of Trichoderma afroharzianum and T. simmonsii) to colonize and stimulate the growth of grapevines. Two commercial vineyards about 400 km away from the site of isolation were used as experimental fields, from which the strains of three Trichoderma species were re-isolated up to four years after rootstock soaking treatment with conidiospores, performed before planting. The treatments decreased the overall percentage of lost plants of about 30%, although a low number of lost plants (about 5%) were observed also in the control plot. For all cultivars and clones, the Trichoderma treatments significantly increased both the bud burst ratio and bud burst vigor index. In addition, the grape must parameters such as the Brix degrees, as well as the extract, the D-glucose and the D-fructose concentrations all appeared to be improved, suggesting a potentially higher ethanol content of the produced wine. We conclude that grapevine-endophytic Trichoderma isolates promote plant growth, which could be a useful feature for sustainable agriculture in general and integrated plant production in particular.

Predominant Clonal Reproduction with Infrequent Genetic Recombination of Phaeoacremonium minimum in Western Cape Vineyards.

Phaeoacremonium minimum is an important esca and Petri disease pathogen that causes dieback of grapevines in South Africa. Little is known regarding the reproductive strategy of the pathogen. Sexual reproduction could lead to a better adaptation of the pathogen to disease management strategies by combining alleles through recombination. The study aimed to investigate the genetic diversity and recombination potential of eight populations in the Western Cape, from six commercial vineyards and two nursery rootstock mother blocks. This was achieved by developing and applying nine polymorphic microsatellites and mating-type-specific markers. Thirty-seven genotypes were identified from 295 isolates. Populations were characterised by the same dominant genotype (MLG20 occurring 65.43%), low genotypic diversity (H) and high numbers of clones (81.36% of dataset). However, genotypes from the same sampling sites were not closely related based on a minimum spanning network and had high molecular variation within populations (94%), suggesting that multiple introductions of different genotypes occurred over time. Significant linkage disequilibrium among loci (r̅d) further indicated a dominant asexual cycle, even though perithecia have been observed in these four populations. The two rootstock mother blocks had unique genotypes and genotypes shared with the vineyard populations. Propagation material obtained from infected rootstock mother blocks could lead to the spread of more genotypes to newly established vineyards. Based on our results, it is important to determine the health status of rootstock mother blocks. Management strategies must focus on reducing aerial inoculum to prevent repeated infections and further spread of P. minimum genotypes.

Limiting carbohydrates to trunk and roots improves bud fruitfulness, fruit set and yield in cv. Malbec

Many commercial vineyards of Malbec, the most cultivated grapevine in Argentina, show unstable yield because of variations in bud fruitfulness and the occurrence of “shatter”, characterised by poor fruit set and fruitlet abscission. Shatter can be due to plant material, growing conditions and meteorological events. Among the parameters that determine fruit set efficiency and vine yield, the availability of carbohydrates (CH) plays an essential role. We previously showed that controlling CH partitioning by removing part of the phloem tissue through an annular incision at the base of the fruit shoots (shoot girdling) reduced shatter in Malbec. The objective of this research was to evaluate the partitioning of CH for the different sink organs of the aerial part of the plant when an interruption of phloem flux from leaves to storage organs is imposed by a girdle. Shoot and trunk girdling trials were conducted during the 2018 and 2019 growing seasons, respectively. At flowering, girdling was performed on different plant lots either at the base of the shoot (Base G), above the distal cluster of the shoot (Top G), to the trunk (Trunk G) or no girdling (Control). Most of the yield components were increased by Base G and Trunk G with no significant impact on vegetative growth or fruit quality. Total shoot biomass was not affected in Base G, while a 39 % reduction was observed in Top G, as compared to Control. The partitioning pattern within the shoot was modified by shoot girdling, and Base G favoured the accumulation of CH towards clusters at the expense of lateral shoots. Shoot girdling increased node diameter, bud fruitfulness and inflorescence dry weight of the shoot. Trunk-girdled vines showed an increase in fruit set and total yield at harvest, with no significant impact on vegetative growth. The restriction of CH flow to the trunk and roots by Base G and Trunk G at flowering increased yield components at harvest without affecting vegetative growth or grape quality. These results reinforce our hypothesis that the root system of the vines under study constitutes a strong sink during the flowering period that competes for CH.