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Nationalité : Britannique / Nationality : British

Domaine de Recherche / Research Area 

How does the graft union form and what factors are important for grafting success ?

Graft compatibility is an essential prerequisite for rootstocks. The aim of this work is to understand the factors important for grafting success using a combination of genomics and genetics approaches. We are characterising the molecular changes occurring during graft union formation in grapevine, such as, spatio-temporal changes in polyphenol concentration at the graft interface (Loupit et al., 2023b). We found that stilbenes accumulate in the wounded xylem parenchyma tissues, whereas naringenin accumulates in the newly formed callus tissues (Figure 1). This pattern of stilbene accumulation suggests that stilbenes have a role in plant defense. Whereas, metabolites accumulated in the newly formed callus tissues presumably have a wider range of roles such as forming new vascular tissues, signaling, defense, and developing a functional graft union. In addition, we are characterising the genes differentially expressed and the metabolites accumulated during graft union formation (Loupit, 2023); this study has provided a list of candidate genes for further analysis. 

One limit to studying the genetic architecture of grafting success is being able to accurately phenotype the graft union because the structure develops heterogeneously and in three dimensions. In addition, successful grafts need to have functional vascular connections between the scion and rootstock, which can not necessarily been assessed by studying structure alone. A range of methods have been used to characterize graft union formation, such as classical histology, non-destructive image analysis, quantifying tracer movement, hydraulic conductivity measurements and quantifying the mechanical strength of the graft union (as reviewed by (Loupit et al., 2023a)), we are currently optimising techniques to quantify different aspects of graft union formation for future genetics studies (Camboué et al., 2023) and using micro-computed tomography/micro-CT to study functional xylem connections between the scion and rootstock (Figure 2).  Because of the difficulty of phenotyping grafting success in large populations much research effort has been devoted to the identification of molecular markers/proxies of grafting success/failure (as reviewed by (Loupit and Cookson, 2020)). We have also used generalized linear models to predict grafting success based on metabolite concentration (Loupit et al., 2022), but these markers are not sufficiently informative to use in genetic studies.

Publications récentes

Camboué M, Loupit G, Janoueix A, Tandonnet JP, Morel M, Marguerit E, Cordelieres FP, Teillon J, Moisy C, Mathieu G, Spilmont AS, Cookson SJ. 2023. Techniques to study graft union formation in grapevine. In: Series IC, ed. GIESCO 2023.

Loupit G. 2023. Comprendre la formation de l’union greffon/porte-greffe et l’incompatibilité de la greffe chez la vigne. Ph.D., Univ. Bordeaux.

Loupit G, Brocard L, Ollat N, Cookson SJ. 2023a. Grafting in plants: recent discoveries and new applications. Journal of Experimental Botany 74, 2433-2447.

Loupit G, Cookson SJ. 2020. Identifying Molecular Markers of Successful Graft Union Formation and Compatibility. Frontiers in Plant Science 11, 610352.

Loupit G, Fonayet JV, Lorensen MDBB, Franc C, De Revel G, Janfelt C, Cookson SJ. 2023b. Tissue-specific stilbene accumulation is an early response to wounding/grafting as revealed by using spatial and temporal metabolomics. Plant, Cell & Environment n/a, 1-16.

Loupit G, Prigent S, Prodhomme D, Spilmont AS, Hilbert G, Franc C, de Revel G, Ollat N, Valls Fonayet J, Cookson SJ. 2022. Identifying early metabolite markers of successful graft union formation in grapevine Horticultural Research 9, uhab070.