Plants are able to naturally graft or inosculate their trunks, branches and roots together, this mechanism is used by humans to graft together different genotypes for a range of purposes. Grafts are ...considered successful if functional vascular connections between the two genotypes occur. Various techniques can evaluate xylem connections across the graft interface. However, these methods are generally unable to assess the heterogeneity and three‐dimensional (3D) structure of xylem vessel connections. Here we present the use of X‐ray micro‐computed tomography to characterize the 3D morphology of grafts of grapevine. We show that xylem vessels form between the two plants of natural root and human‐made stem grafts. The main novelty of this methodology is that we were able to visualize the 3D network of functional xylem vessels connecting the scion and rootstock in human‐made stem grafts thanks to the addition of a contrast agent to the roots and improved image analysis pipelines. In addition, we reveal the presence of extensive diagonal xylem connections between the main axial xylem vessels in 2‐year old grapevine stems. In conclusion, we present a method that has the potential to provide new insights into the structure and function of xylem vessels in large tissue samples.
Summary statement
Successful grafting requires the formation of functional vascular connections between two different plants. We describe using X‐ray micro‐computed tomography to characterize the network of xylem vessels formed across the graft interface of natural root and human‐made stem grafts of grapevine.
Quantifying healthy and degraded inner tissues in plants is of great interest in agronomy, for example, to assess plant health and quality and monitor physiological traits or diseases. However, ...detecting functional and degraded plant tissues in-vivo without harming the plant is extremely challenging. New solutions are needed in ligneous and perennial species, for which the sustainability of plantations is crucial. To tackle this challenge, we developed a novel approach based on multimodal 3D imaging and artificial intelligence-based image processing that allowed a non-destructive diagnosis of inner tissues in living plants. The method was successfully applied to the grapevine (Vitis vinifera L.). Vineyard's sustainability is threatened by trunk diseases, while the sanitary status of vines cannot be ascertained without injuring the plants. By combining MRI and X-ray CT 3D imaging with an automatic voxel classification, we could discriminate intact, degraded, and white rot tissues with a mean global accuracy of over 91%. Each imaging modality contribution to tissue detection was evaluated, and we identified quantitative structural and physiological markers characterizing wood degradation steps. The combined study of inner tissue distribution versus external foliar symptom history demonstrated that white rot and intact tissue contents are key-measurements in evaluating vines' sanitary status. We finally proposed a model for an accurate trunk disease diagnosis in grapevine. This work opens new routes for precision agriculture and in-situ monitoring of tissue quality and plant health across plant species.
Since its identification in 2003, grapevine Pinot gris virus (GPGV,
Trichovirus
) has now been detected in most grape-growing countries. So far, little is known about the epidemiology of this newly ...emerging virus. In this work, we used datamining as a tool to monitor
in-silico
the sanitary status of three vineyards in Italy. All data used in the study were recovered from a work that was already published and for which data were publicly available as SRA (Sequence Read Archive, NCBI) files. While incomplete, knowledge gathered from this work was still important, with evidence of differential accumulation of the virus in grapevine according to year, location, and variety-rootstock association. Additional data regarding GPGV genetic diversity were collected. Some advantages and pitfalls of datamining are discussed.
► X-ray tomography was used to study the graft interface in grapevine. ► The structure of the tissues of the graft interface could be visualized. ► Differences between “good” and “bad” quality grafts ...were evident. ► It is the first time, that the junctions between scion and rootstock are revealed in 3D. ► This could be a novel method to evaluate future rootstocks and scion genotypes.
Successful grafting in plants requires the development of a functional vascular system between the scion and the rootstock. Understanding the spatial organization of the graft interface is important to the evaluation of new rootstock genotypes and to the development of new grafting technologies. Until now the graft interface has only been studied using 2D classical histology and low resolution 3D magnetic resonance imaging. Here we investigate the ability of X-ray tomography to examine the graft interface of Vitis vinifera in high resolution and in 3D.
Data were collected using a Skyscan 1076, scanning parameters, such as, X-ray energy, filter selection, pixel size and rotation angles, were optimized to study the particularities of the graft interface. The X-ray tomography technique was then used to evaluate graft quality. Two young vines were compared; one graft was classified as of ‘good’ quality, whereas the other was classified as of ‘bad’ quality. We were able to distinguish the “omega cut”, the pith, the phloem and the xylem vessels in the images. The analysis shows several differences between the two vines. In the good graft, tissues appear well-connected in the wood and phloem, and had a regular structure; the wood appears homogenous with a lot of vessels that form a compact mass. By contrast, in the bad graft, the structures appear disorganized and not completely connected.
Numerous new vessels, continuous between the scion and the rootstock, are visible in the “good graft” whereas only few ones are visible in the “bad one”. It is the first time, to our knowledge, that 3D imaging of the graft interface and the vascular connections across it have been reported, opening new avenues for graft quality assessment in woody plants.
Beside the well-known fungal pathologies, grapevine virus diseases are of major importance in grapegrowing areas, also due to the limited knowledge by the professionals of the sector. To face this ...problem, the PAThOGEN training program was developed, with the aims of: (i) building a high-quality Vocational and Education Training program, (ii) improving the skills of the main actors of the wine sector. The pilot courses were developed in two levels (Basic and Advanced) and made available on a dedicated online platform in 4 languages (French, Italian, Spanish and English). Moreover, two field sessions were organized in each of the 3 partner countries in order to complete the theoretical training. A specific feature of this project was the “demand driven approach” used to conceive the courses. Indeed, a panel of experts and 128 “student-testers” were selected in the 3 countries in the different professional categories to test the training program. 98% of the testers evaluated the training course as “interesting” or “very interesting”. The detailed evaluations allowed us to rework the courses both in terms of content and functionality. The elearning training is now available in the four languages, and the field training is annually organized in France, Italy and Spain.
Grapevine red blotch virus (GRBV) is a recently identified virus that infects grapevine and has a severe impact on the grape industry in North America. Since the first description of the virus 8 ...years ago, clear progress has been made regarding our understanding of the GRBV pathosystem. However, questions remain regarding the origin of this pathogen and its spread outside North America, especially in Europe. In this study, we present the results of a large-scale GRBV survey in two European repositories; we targeted
Vitis
spp. accessions with diverse geographical origins. Of 816 accessions from different origins (50 different countries around the world), six accessions were infected by GRBV, all of which originated from the United States. We investigated the DNA virome of 155 grapevine accessions from the Swiss grapevine collection using high-throughput sequencing. We observed that virome of the Swiss grapevine collection was composed of several RNA viruses. In contrast, we did not detect any DNA viruses in the 155 Swiss grapevine accessions. This finding suggests that the abundance of DNA viruses infecting grapevines in Switzerland is either very low or non-existent. Our results and the findings of studies published since 2008 show that GRBV most likely originated in North America and subsequently spread to other viticultural areas in the world via unintentional movement of infected cuttings. According to our data, the most plausible scenario for the origin of GRBV is that the virus evolved from non-
Vitis vinifera
hosts and underwent a host jump to
Vitis vinifera
after its introduction to North America in the 1600s.
Since its identification in 2003, little has been revealed about the spread of grapevine Pinot gris virus (GPGV), an emerging grapevine virus. According to studies from Italy, GPGV transmission in ...the vineyard can be fast but progressive over the years. To gain new insights into the spread of GPGV infections, we tested 67 grapevines in a single vineyard parcel in southern France. These vines were sampled over 8 years (2013 to 2020) and tested for GPGV by reverse-transcription PCR using a new primer pair designed from the recently described genetic diversity of GPGV worldwide. While focusing on a portion of the samples (n = 20), we observed a drastic increase in newly GPGV-infected vines from 2014 (5%, 1 of 20) to 2015 (80%, 16 of 20) and 2016 (90%, 18 of 20). Infected vines were scattered throughout the vineyard with no distinct pattern of distribution, and some rare vines remained negative through 2020. Using all available genomic information, we performed Bayesian-based phylogeographic analyses that identified a major intravineyard transmission in 2014 to 2015. To test our model, we analyzed 47 additional grapevines and confirmed the outbreak of GPGV in 2015, validating our in silico projection. Interestingly, some grapevines remained negative throughout the study, in spite of their close proximity to infected plants. These results raise questions about the dynamics of vector populations and environmental conditions that may be required for virus spread to occur in the vineyard.
Abstract
Grafting is an important horticultural technique used for many crop species. However, some scion/rootstock combinations are considered as incompatible due to poor graft union formation and ...subsequently high plant mortality. The early identification of graft incompatibility could allow the selection of non-viable plants before planting and would have a beneficial impact on research and development in the nursery sector. In general, visible phenotypes of grafted plants (size, root number, etc.) are poorly correlated with grafting success, but some studies have suggested that some polyphenols could be used as markers of graft incompatibility several months or years after grafting. However, much of the previous studies into metabolite markers of grafting success have not included all the controls necessary to unequivocally validate the markers proposed. In this study, we quantified 73 primary and secondary metabolites in nine hetero-grafts and six homo-grafted controls 33 days after grafting at the graft interface and in both the scion and rootstock woody tissues. Certain biomarker metabolites typical of a high stress status (such as proline, GABA and pallidol) were particularly accumulated at the graft interface of the incompatible scion/rootstock combination. We then used correlation analysis and generalized linear models to identify potential metabolite markers of grafting success measured one year after grafting. Here we present the first attempt to quantitatively predict graft compatibility and identify marker metabolites (especially asparagine, trans-resveratrol, trans-piceatannol and α-viniferin) 33 days after grafting, which was found to be particularly informative for homo-graft combinations.
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