X-ray tomography: a promising tool to assess the selection of good quality grafted vines

Abstract

The production of grated vines is a complex process from grafting to final sorting in nurseries. To reach the market, grafted grapevines must meet three criteria by law in France: resistance to a manual graft union test (named thumb test), a minimum number of three roots and a woody shoot of at least 2 cm long. The thumb test is in essence unmeasurable in view of its manual and subjective execution and does not allow to evaluate the internal quality of the junctions. The development of tools and medical imaging methods may help to assess the internal quality of the graft union.

Commonly used in the medical field to identify some pathologies, X-ray tomography is also used in other fields including plant biology because of its ability to image structures in depth. Previous work on vines has shown its interest to distinguish the pith, the phloem, the xylem vessels and the necrotic tissues. We decided to investigate its ability to identify possible internal criteria relevant to the selection of good quality grafted vines prior to marketing. 

We therefore developed a specific methodology in terms of scanning parameters, 3D reconstruction and images analysis able to be used onto many plants. It was then applied onto 110 vines, Omega-grafted, just before being sorted. Different internal anatomical and functional criteria were measured in the rootstock, the scion and the graft area. Two criteria (“Quantity of xylem produced after grafting” and “Air and necrosis volume in the grafting area”) appeared interesting because they present statically different values on the batches that pass or not the sorting process.