Grapevine Buds Research Articles

Buds of “Italia melhorada” grapevines grown under tropical conditions develop a quiescent state

A double cropping system for the grapevine (Vitis vinifera L) has been commercially adopted for use in regions where the tropical climate is characterized by high temperatures and small variations in daylength throughout the year. Under these climatic conditions, the use of hydrogen cyanamide (HC), a compound that breaks bud dormancy, is mandatory to produce homogeneous budbreak. However, it is unknown whether grapevine buds are capable of developing endodormancy (ED) under these climatic conditions. In this study, typical signals of ED, such as the number of nodes per cane, the development of periderm and the thickening of the cell wall of the bud meristematic cells, were analysed in vines of “Italia melhorada” grown in Mossoró, Brazil (5°12′16″S), under a natural (ND) photoperiod (12/12 h), a short-day (SD) photoperiod (10/14 h) and a long-day (LD) photoperiod (14/10 h). The abundance of phytochrome A (VvPHYA) and B (VvPHYB) and FLOWERING LOCUS T (VvFT) transcripts in the leaves and buds was also determined. The results showed a reduced number of nodes per cane and development of the periderm in the shoots of grapevines grown under ND and SD photoperiods. In addition, compared with that under the LD photoperiod, the expression of VvPHYA and VvFT under the ND and SD-photoperiod decreased, and the expression of VvPHYB increased. However, the thickness of the cell wall of the bud meristematic cells increased only in the grapevines exposed to the SD photoperiod. Therefore, we hypothesize that cell wall thickening is a characteristic of ED, while decreased expression of VvPHYA and VvFT and increased expression of VvPHYB are characteristic of quiescence. Consequently, under a tropical conditions, the grapevine buds would be in a quiescent state and not in a dormant state.

Ethanol sprays to release grapevine bud dormancy: a potential alternative to cyanamides

Aim: Grape growers sometimes use cyanamides (calcium or hydrogen) to release bud dormancy in warm climate regions, where the chilling requirement has not been met during winter. However, these products can cause damage to plants and are dangerous to handle, so alternatives would be welcomed by growers. Connections between metabolisms of ethanol, ethylene and cyanide revealed by previous studies led us to test the potential of ethanol sprays on bud break and early shoot growth.Methods and results: Trials were performed over three years on Vitis vinifera grapevines trained in Guyot or cordon, and on cuttings in growth chambers. Cultivars used in the studies included Cabernet-Sauvignon, Syrah and Ugni blanc. The results show that ethanol can advance bud break of all three cultivars at concentrations ranging from 2.5 to 10 % ethanol in water. Ethanol stimulates bud development in both Guyot and cordon training systems. However, the timing of ethanol application is crucial, and late spring season applications reduce the effectiveness of the treatment.Conclusions: Observations were performed over three different seasons. The trials revealed that ethanol sprays can advance bud break of different Vitis vinifera vines, trained with cane or spur systems.Significance and impact of the study: Climate change impacts dormancy release, making it an increasingly important issue over the next few decades. An alternative to the dangerous use of cyanamides to promote bud break would greatly help growers. These preliminary results with ethanol are promising but should lead to trials in various growing areas and with various cultivars in order to confirm their potential for viticulture.

X-ray phase contrast imaging of Vitis spp. buds shows freezing pattern and correlation between volume and cold hardiness

Grapevine (Vitis spp.) buds must survive winter temperatures in order to resume growth when suitable conditions return in spring. They do so by developing cold hardiness through deep supercooling, but the mechanistic process of supercooling in buds remains largely unknown. Here we use synchrotron X-ray phase contrast imaging to study cold hardiness-related characteristics of V. amurensis, V. riparia, and V. vinifera buds: time-resolved 2D imaging was used to visualize freezing; and microtomography was used to evaluate morphological changes during deacclimation. Bud cold hardiness was determined (low temperature exotherms; LTEs) using needle thermocouples during 2D imaging as buds were cooled with a N2 gas cryostream. Resolution in 2D imaging did not allow for ice crystal identification, but freezing was assessed by movement of tissues coinciding with LTE values. Freezing was observed to propagate from the center of the bud toward the outer bud scales. The freezing events observed lasted several minutes. Additionally, loss of supercooling ability appears to be correlated with increases in bud tissue volume during the process of deacclimation, but major increases in volume occur after most of the supercooling ability is lost, suggesting growth resumption processes are limited by deacclimation state.

Mapping the genetic architecture of grapevine bud growth-cycling quantitative traits

Mapping the genetic architecture of grapevine bud growth-cycling quantitative traits

A New Measurement Model to Estimate the Intensity of Acrotony on the Latent Buds of Grapevine Canes (Vitis vinifera L.)

In warm regions, such as in southern Greece, the climate change can lead to prolonged dormancy as well as to problems in bud dormancy (delay in breaking time, reduce the rate of budbreak, intensity of the phenomenon of acrotony, grapevine bud fall, disorders in bloom with intense blossom dropping, etc.), with a significant impact on the production of the vines. In these areas, it is necessary to apply chemical substances in order to break the dormancy and advance budbreak, especially when it comes to new table grape varieties, most of which are seedless. Another phenomenon which is observed on grapevines and is directly associated with budbreak is acrotony, where the apical buds of the cane break first compared to the middle and basal ones. Acrotony can constitute a problem because it can cause irregular grape ripening, different timing of various activities in the vineyard, which brings about higher cultivation costs. In this research, a new method to measure and evaluate the acrotony and its intensity on the latent buds of grapevine canes was described. The results of two chemical substances applied on table grape variety ‘Prime’ in order to advance budbreak were presented.
 
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 In press - Online First. Article has been peer reviewed, accepted for publication and published online without pagination. It will receive pagination when the issue will be ready for publishing as a complete number (Volume 47, Issue 3, 2019). The article is searchable and citable by Digital Object Identifier (DOI). DOI link will become active after the article will be included in the complete issue.
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ABA and its signaling pathway are involved in the cold acclimation and deacclimation of grapevine buds

The grapevine (Vitis vinifera L.) buds as well as the buds of other deciduous fruit trees acclimate and deacclimate to the cold during the autumn-winter season. Cold acclimation (CA) is characterized by an increase in bud cold-hardiness, while deacclimation (DA) by a loss of it. The mechanisms underlying the transition of the buds from CA to DA are not well understood. In this study, the effect of ABA, LT and ABA + LT on the expression of the genes of the ABA signaling pathway, and the role that these genes and ABA play in the transition of the buds from the CA to the DA was investigated. In vitro experiments carried-out with single-bud cuttings were used to analyze the effect of ABA, LT and ABA + LT treatments on the expression of ABA signaling genes. To study the role of ABA and its signaling pathway in the transition of grapevine buds from CA to DA, applications of ABA and Uniconazole-P (Uni-P), an inhibitor of the enzyme that catabolizes ABA, were performed to the grapevine buds during their period of CA and DA. The results show that : a) VvPP2Cs were the only ABA signaling genes which were induced synergistically by ABA + LT, b) ABA improved the cold-hardiness of the buds only during its period of CA c) Uni-P advanced the appearance of the second peak of ABA in the buds and its transition from the CA to the DA.

Karaerik Üzüm Çeşidinin Kış Gözlerindeki Soğuk Zararının Tarla ve Laboratuvar Koşullarında Belirlenmesi

This study was conducted to detect cold damage in dormant buds of grapevine under field (by shooting test) and laboratory (by sectioning method) conditions. In the determination of the low temperature damage, it has been investigated whether there is a difference between the method of sectioning in laboratory conditions and the real shooting level in the field conditions . The study was carried out in the vineyard which was established with the Karaerik ( V. vinifera L. ) grape cultivar in the Uzümlü district of Erzincan in 2012, 2013 and 2014. Samples of an old grapevine cuttings from the vineyard was transported to the laboratory on the same day and sections were taken in order to determine the damage level. Cold damage was assessed based on 1-4 bud averages. In addition, cold damage was evaluated separately in 1st, 2nd, 3rd and 4th nodes. The mortality rates of primary and secondary buds for the first 1-4 buds average were determined and the vitality rates of tertiary buds were determined in order to determine the ultimate vitality. At the second stage of study, the mortality rates (%) of primary and secondary buds and the viability rates (%) of tertiary buds were determined by counting in spring the shoots come from the primary, secondary, and tertiary buds of the first 4 buds that were left in pruning in vineyard. Secondary and tertiary buds were also considered alive if the primary buds have sprouted in vineyard. In the study that determined the level of damage of the buds, it was found that the difference between the sectioning method and the shooting test was 7.9% in primary buds, 14.56% in secondary buds, and 0.1% in tertiary buds . The mortality rates of primary buds and the viability rates of tertiary buds were found statistically insignificant differences between the methods, but the mortality rates of the secondary buds were found statistically significant differences between the methods.

Grapevine bud fertility under conditions of elevated carbon dioxide

Aims: Microscopic bud dissection is commonly used to assess grapevine bud fertility and thereby predict yield for the following season. Grapevine yield has been shown to increase in response to elevated carbon dioxide concentration (eCO2), and this yield gain has been demonstrated under Free Air Carbon dioxide Enrichment (FACE). However, the effects of eCO2 on bud fertility and their relation to yield gain have not been investigated. Little is known about which stages of development and which yield components are affected. The aim of this study was to determine the number of inflorescence primordia (IP) per node, the cross-sectional area of the IP, and the incidence of primary bud necrosis (PBN) in grapevine compound buds grown under conditions of ambient CO2 concentration (aCO2) and eCO2, and to relate the data to yield parameters of field-grown vines at harvest.Methods and results: Plant material was collected in February 2016 and February 2017 from two Vitis vinifera L. cultivars, Riesling and Cabernet-Sauvignon, growing at the VineyardFACE experimental site of Hochschule Geisenheim University (49°59¢N, 7°57¢E) in the Rheingau wine region, Germany. Bud dissections were performed at the University of Adelaide’s Waite Research Institute, Australia. Canes were stored at 4°C until dissection at room temperature. The first eight nodes of each cane were dissected and the compound buds assessed; IP number, IP cross-sectional area (evaluated by image analysis) and PBN incidence were recorded. In Riesling, no differences were found between plants grown under the two CO2 treatments in terms of IP number per node or subsequent number of bunches per shoot. Compound buds of Riesling plants grown under eCO2 had larger IP cross-sectional area; however, this did not result in higher bunch weight or yield in response to eCO2 over the 2 years. In Cabernet-Sauvignon, IP number per node was higher in plants grown under eCO2 but no changes in bunch number per shoot were found in either season. In contrast, the larger IP cross-sectional area in Cabernet-Sauvignon in response to eCO2 translated into higher bunch weight and yield in both seasons. PBN incidence of both cultivars was highest at basal node positions along the fruiting cane, except for Cabernet-Sauvignon in 2017, where both treatments showed higher incidence at the distal ends. In both cultivars, average PBN incidence along the cane was unaffected by eCO2.Conclusions: Microscopic bud dissection can be used at an early stage of vine development to predict increased bunch weight. There was evidence of a cultivar-dependent response to eCO2 in terms of bud fruitfulness. In future, it would be interesting to investigate whether higher carbohydrate levels are responsible for the increase in IP area detectable at a very early stage of development in plants grown under eCO2.Significance and impact of the study: The findings of this study contribute to our understanding of grapevine bud fertility and yield potential, particularly under changing climatic conditions.

The initiation of bud burst in grapevine features dynamic regulation of the apoplastic pore size.

The physiological constraints on bud burst in woody perennials, including vascular development and oxygenation, remain unresolved. Both light and tissue oxygen status have emerged as important cues for vascular development in other systems; however, grapevine buds have only a facultative light requirement, and data on the tissue oxygen status have been confounded by the spatial variability within the bud. Here, we analysed apoplastic development at early stages of grapevine bud burst and combined molecular modelling with histochemical techniques to determine the pore size of cell walls in grapevine buds. The data demonstrate that quiescent grapevine buds were impermeable to apoplastic dyes (acid fuchsin and eosin Y) until after bud burst was established. The molecular exclusion size was calculated to be 2.1 nm, which would exclude most macromolecules except simple sugars and phytohormones until after bud burst. We used micro-computed tomography to demonstrate that tissue oxygen partial pressure data correlated well with structural heterogeneity of the bud and differences in tissue density, confirming that the primary bud complex becomes rapidly and preferentially oxygenated during bud burst. Taken together, our results reveal that the apoplastic porosity is highly regulated during the early stages of bud burst, suggesting a role for vascular development in the initial, rapid oxygenation of the primary bud complex.

ABA promotes starch synthesis and storage metabolism in dormant grapevine buds

In grapevine (Vitis vinifera L.) buds, the short day (SD)-photoperiod induces endodormancy and increases the level of ABA and the expression of ABA key biosynthesis genes, which suggests that ABA could be the mediator of the photoperiodic induction of endodormancy. In the present study, it was established that during the development of the endodormancy, the content of ABA and the accumulation of starch increased in parallel in the buds; however, these increases occurred after the buds were already in the state of endodormancy. Despite this finding the exogenous applications of ABA to single-bud cuttings increased the starch content and up-regulated the expression of starch synthesis genes (VvSS1 and VvSS3) and down-regulated the expression of sucrose metabolism genes, invertase (VvINV) and sucrose phosphate synthase (VvSUPS). In addition, the manipulation of the endogenous content of ABA in the grapevine buds by applications of hydrogen cyanamide and uniconazole-P, revealed that the depth of the endodormancy depends on the ABA levels. Taken together, the results indicate that the development of the endodormancy in grapevine buds is associated with the accumulation of starch and a shift in metabolism towards a storage metabolism; as ABA stimulates both processes, it must play an important role in the maintenance and release but not the induction of endodormancy in grapevine buds.

Abscisic acid (ABA) and low temperatures synergistically increase the expression of CBF/DREB1 transcription factors and cold-hardiness in grapevine dormant buds.

It has been reported that low temperatures (LTs) and the plant hormone abscisic acid (ABA) induce the expression of CBF/DREB1 transcription factors in vegetative tissues and seedlings of Vitis vinifera and Vitis riparia and that foliar applications of ABA to V. vinifera increase the freezing tolerance or cold-hardiness of dormant buds. However, the combined effect of ABA and LTs on the expression of CBF/DREB1 transcription factors and on the acquisition of freezing tolerance in dormant grapevine buds has not been investigated. The objective of this study was to analyse the combined effect of ABA and LT treatments on the expression of CBF/DREB transcription factors and the acquisition of freezing tolerance. In vitro experiments with single-bud cuttings of grapevines were used to analyse the effect of ABA, ABA + LT and LT on the expression of CBF/DREB transcription factors, dehydrin and antioxidant genes, the acquisition of freezing tolerance and the endogenous content of ABA. Gene expression analysis was performed by quantitative real-time PCR and freezing tolerance was determined by measuring the low-temperature exotherm by differential thermal analysis. ABA levels were determined by gas chromatography coupled to an electron capture detector. The LT treatment and exogenous application of ABA to grapevine dormant buds increased the expression of the CBF/DREB1 transcription factors VvCBF2, VvCBF3, VvCBF4 and VvCBF6. The joint application of LT and ABA produced a huge increase in the expression of these transcription factors, which was greater than the sum of the increases produced by them individually, which indicates the existence of a synergistic effect between ABA and LT on the activation of these transcription factors. This synergic effect was also observed on the increase in bud cold-hardiness and on the expression of antioxidant and dehydrin genes. The synergy between ABA and LT on the expression of CBF/DREB1 transcription factors VvCBF2, VvCBF3, VvCBF4 and VvCBF6 plays a key role in cold acclimatization of grapevine buds. The results highlight the importance of the combination of stimuli in the improvement of genetic and physiological responses and help us to understand the adaption of plants to complex environments.

Transient induction of a subset of ethylene biosynthesis genes is potentially involved in regulation of grapevine bud dormancy release.

Transient increases in ethylene biosynthesis, achieved by tight regulation of transcription of specific ACC oxidase and ACC synthase genes, play a role in activation of grapevine bud dormancy release. The molecular mechanisms regulating dormancy release in grapevine buds are as yet unclear. It has been hypothesized that its core involves perturbation of respiration which induces an interplay between ethylene and ABA metabolism that removes repression and allows regrowth. Roles for hypoxia and ABA metabolism in this process have been previously supported. The potential involvement of ethylene biosynthesis in regulation of dormancy release, which has received little attention so far, is now explored. Our results indicate that (1) ethylene biosynthesis is induced by hydrogen cyanamide (HC) and azide (AZ), known artificial stimuli of dormancy release, (2) inhibitors of ethylene biosynthesis and signalling antagonize dormancy release by HC/AZ treatments, (3) ethylene application induces dormancy release, (4) there are two sets of bud-expressed ethylene biosynthesis genes which are differentially regulated, (5) only one set is transiently upregulated by HC/AZ and during the natural dormancy cycle, concomitant with changes in ethylene levels, and (6) levels of ACC oxidase transcripts and ethylene sharply decrease during natural dormancy release, whereas ACC accumulates. Given these results, we propose that transient increases in ethylene biosynthesis prior to dormancy release, achieved primarily by regulation of transcription of specific ACC oxidase genes, play a role in activation of dormancy release.

Deacclimation kinetics as a quantitative phenotype for delineating the dormancy transition and thermal efficiency for budbreak in Vitis species.

Bud dormancy and cold hardiness are critical adaptations for surviving winter cold stress for temperate perennial plant species. In grapevine, acquisition of cold hardiness requires dormancy induction in the early winter and careful maintenance of dormancy state throughout winter. With sufficient exposure to low, non-freezing temperatures (chilling requirement), grapevine buds transition between early (endodormant) and late winter (ecodormant) states. The objective of this study was to uncover the relationship between fulfilment of the chilling requirement and the effects of various temperatures on loss of cold hardiness (deacclimation). The relationship between chilling requirement and temperature as it affects the rate of deacclimation (kdeacc) was examined for dormant cuttings of Vitis vinifera, V. aestivalis, V. amurensis and V. riparia. The effect of temperature on kdeacc was exponential at low and logarithmic at high temperatures. Deacclimation rates also increased in magnitude as chilling accumulated demonstrating a change in deacclimation potential (Ψdeacc), following a logarithmic response. The combination of Ψdeacc and kdeacc indicates genotype-specific thermal efficiency for deacclimation and growth in Vitis that may be overlooked by simple growing degree-day computations. The Ψdeacc and kdeacc parameters are genotype-specific and will greatly increase the refinement of models predicting effects of climate change on phenology. Deacclimation rates represent a quantitative determinant of dormancy transition and budbreak in grapevine and will assist researchers in selecting germplasm for differences in chilling requirement and thermal efficiency.

Chilling requirements and dormancy evolution in grapevine buds

ABSTRACT Fluctuations in winter chilling availability impact bud dormancy and budburst. The objective of this work was to determine chilling requirements to induce and overcome endodormancy (dormancy controlled by chilling) of buds in different grape cultivars. ‘Chardonnay’, ‘Merlot’ and ‘Cabernet Sauvignon’ shoots were collected in Veranópolis-RS vineyards in 2010, and submitted to a constant 3 °C temperature or daily cycles of 3/15 °C for 12/12h or 18/6h, until reaching 1120 chilling hours (CH, sum of hours with temperature ≤ 7.2 °C). Periodically, part of the samples in each treatment was transferred to 25 °C for budburst evaluation (green tip). Chilling requirements to induce and overcome endodormancy vary among cultivars, reaching a total of 136 CH for ‘Chardonnay’, 298 CH for ‘Merlot’ and 392 CH for ‘Cabernet Sauvignon’. Of these, approximately 39, 53 and 91 CH are required for induction of endodormancy in the three cultivars, respectively. The thermal regimes tested (constant or alternating) do not influence the response pattern of each cultivar to cold, with 15 °C being inert in the CH accumulation process. In addition, time required to start budburst reduces with the increase in CH, at a rate of one day per 62 CH, without significant impacts on budburst uniformity.

Abscisic acid catabolism enhances dormancy release of grapevine buds.

The molecular mechanism regulating dormancy release in grapevine buds is as yet unclear. It was formerly proposed that dormancy is maintained by abscisic acid (ABA)-mediated repression of bud-meristem activity and that removal of this repression triggers dormancy release. It was also proposed that such removal of repression may be achieved via natural or artificial up-regulation of VvA8H-CYP707A4, which encodes ABA 8'-hydroxylase, and is the most highly expressed paralog in grapevine buds. The current study further examines these assumptions, and its experiments reveal that (a) hypoxia and ethylene, stimuli of bud dormancy release, enhance expression of VvA8H-CYP707A4 within grape buds, (b) the VvA8H-CYP707A4 protein accumulates during the natural transition to the dormancy release stage, and (c) transgenic vines overexpressing VvA8H-CYP707A4 exhibit increased ABA catabolism and significant enhancement of bud break in controlled and natural environments and longer basal summer laterals. The results suggest that VvA8H-CYP707A4 functions as an ABA degrading enzyme, and are consistent with a model in which the VvA8H-CYP707A4 level in the bud is up-regulated by natural and artificial bud break stimuli, which leads to increased ABA degradation capacity, removal of endogenous ABA-mediated repression, and enhanced regrowth. Interestingly, it also hints at sharing of regulatory steps between latent and lateral bud outgrowth.

Cellulose nanocrystals reduce cold damage to reproductive buds in fruit crops

Every year tree fruit and grape growers suffer significant economic losses from cold damage to reproductive buds. A combination of pre-planned passive and active frost protection methods has been prevalently used to achieve some level of protection. Herein, we describe a new effective approach to protecting reproductive fruit buds from cold damage. Electrostatic application of cellulose nanocrystals (CNC) dispersion to fruit buds forms a thermal insulation layer with low thermal conductivity (0.061 W m−1 K−1). The dispersion was applied to dormant grapevine (Vitis vinifera) buds, and hardiness was evaluated by differential thermal analysis (DTA). CNC-treated buds were more resistant to freezing temperatures than untreated buds. Cold hardiness was improved by 2–4 °C with CNC treatment. The hardiness of sweet cherry (Prunus avium L.) reproductive buds at the ‘first white’ stage of development was also tested comparing CNC-treated (2% mass) and non-treated clusters. Pistil mortality was evaluated 24 h after treatment. Untreated pistils were killed at ca. −1 °C while the CNC-treated buds were hardy to ca. −4 °C. The temperature at which ca. 10%, 50%, or 90% of untreated pistils were killed was ca. −1.5 °C, −2.8 °C and −5.5 °C, the temperature at which ca. 10%, 50%, or 90% of treated pistils were killed was ca. −4.4 °C, −6.5 °C and −7.7 °C. In general, CNC treatment improved cold-hardiness of grape and sweet cherry buds by about 2–4 °C. These results demonstrate great potential for field applications of CNC to improve speciality crop yield security by protecting reproductive buds from cold damage.

Shotgun proteomic analysis of photoperiod regulated dormancy induction in grapevine

Certain grapevine genotypes become dormant in response to decreasing photoperiod and others require low temperature or both environmental cues to induce dormancy. This study used a proteomic approach to gain an understanding of the underlying molecular events involved in bud dormancy commitment. Two F2 siblings (F2-110 and F2-040) with differences in photoperiod induced dormancy responsiveness were subjected to long day (LD, 15 h, paradormancy maintenance or dormancy inhibition) or short day (SD, 13 h, endodormancy commitment) treatment. Proteins were extracted at two time points (28 days and 42 days) of LD and SD photoperiod exposure, and label-free quantitative shotgun proteomic analysis was performed for three biological replicates of each treatment and time point. A total of 1577 non-redundant proteins were identified in the combined dataset of eight different conditions (2 genotypes, 2 photoperiods and 2 timepoints, available via ProteomeXchange with identifier PXD001627). Genotype specific patterns of budbreak and protein expression were detected in response to the differential photoperiod treatment at the two time points. Peroxidases, dehydrogenases and superoxide dismutases were more abundant at 42 SD than at 28 SD in the dormancy responsive F2-110, suggesting that oxidative stress response related proteins could be markers of endodormancy commitment in grapevine buds.

Grapevine buds detection and localization in 3D space based on Structure from Motion and 2D image classification

In viticulture, there are several applications where 3D bud detection and localization in vineyards is a necessary task susceptible to automation: measurement of sunlight exposure, autonomous pruning, bud counting, type-of-bud classification, bud geometric characterization, internode length, and bud development stage. This paper presents a workflow to achieve quality 3D localizations of grapevine buds based on well-known computer vision and machine learning algorithms when provided with images captured in natural field conditions (i.e., natural sunlight and the addition of no artificial elements), during the winter season and using a mobile phone RGB camera. Our pipeline combines the Oriented FAST and Rotated BRIEF (ORB) for keypoint detection, a Fast Local Descriptor for Dense Matching (DAISY) for describing the keypoint, and the Fast Approximate Nearest Neighbor (FLANN) technique for matching keypoints, with the Structure from Motion multi-view scheme for generating consistent 3D point clouds. Next, it uses a 2D scanning window classifier based on Bag of Features and Support Vectors Machine for classification of 3D points in the cloud. Finally, the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) for 3D bud localization is applied. Our approach resulted in a maximum precision of 1.0 (i.e., no false detections), a maximum recall of 0.45 (i.e. 45% of the buds detected), and a localization error within the range of 259–554 pixels (corresponding to approximately 3 bud diameters, or 1.5 cm) when evaluated over the whole range of user-given parameters of workflow components.

Renewal of vascular connections between grapevine buds and canes during bud break

Abstract With the seasonal change from winter to spring, grapevine compound buds break dormancy and start a new annual developmental cycle. The rebuilding of vascular connections between buds and canes is vital to ensure normal development of the bud. We monitored the dynamic development of grapevine buds under natural field conditions, observed vascular connections using light microscopy, and investigated the uptake and transport of water in buds and canes from dormancy to bud break. During dormancy, the bud was isolated from the cane and no xylem was observed in the bud or the junction region between the bud and the cane. However, at the stage of bud swelling (stage II), xylem was observed at the cane to bud junction. The rate of water uptake through the xylem at the junction increased as bud development progressed. These results suggest that buds were hydraulically isolated from the cane during dormancy and the formation of xylem between bud and cane started with swelling of the bud. The velocity of water transport into the bud also increased with bud development. We discuss several factors that affect the formation and differentiation of xylem, including temperature, hormones and water. It is likely that the rebuilding of vascular connections between buds and canes is related to multiple factors rather than any one individual factor.

Distinct gibberellin functions during and after grapevine bud dormancy release.

The molecular mechanism regulating dormancy release in grapevine buds is as yet unclear. It has been hypothesized that (i) abscisic acid (ABA) represses bud-meristem activity; (ii) perturbation of respiration induces an interplay between ethylene and ABA metabolism, which leads to removal of repression; and (iii) gibberellin (GA)-mediated growth is resumed. The first two hypothesis have been formally supported. The current study examines the third hypothesis regarding the potential involvement of GA in dormancy release. We found that during natural dormancy induction, levels of VvGA3ox, VvGA20ox, and VvGASA2 transcripts and of GA1 were decreased. However, during dormancy release, expression of these genes was enhanced, accompanied by decreased expression of the bud-expressed GA-deactivating VvGA2ox. Despite indications for its positive role during natural dormancy release, GA application had inhibitory effects on bud break. Hydrogen cyanamide up-regulated VvGA2ox and down-regulated VvGA3ox and VvGA20ox expression, reduced GA1 levels, and partially rescued the negative effect of GA. GA had an inhibitory effect only when applied simultaneously with bud-forcing initiation. Given these results, we hypothesize that during initial activation of the dormant bud meristem, the level of GA must be restricted, but after meristem activation an increase in its level serves to enhance primordia regrowth.