The role of phytoplasma effector interaction with phosphoglucomutase in the pathogenicity of ‘Candidatus Phytoplasma solani’ in grapevine 

The characterization of the plant is the obliged pathway between the environment and the product. The responses of the plant amplify or reduce the variations of the environment, while determining directly the type and the quality of the products. These results are inscribed inside the Viticultural Terroir Unit (VTU). VTU is the complex interaction between the Basic Terroir Unit or BTU (interaction mesoclimate x soil/subsoil), the genotype (variety x rootstock), the management system, the oenological technologies. Thus, at the most complex level, a global biological triptych is found again : environment (source) x plant (structure) = produced and exchanged substances.

The postharvest dehydration of grapes is a traditional practice to obtain wines with unique traits (e.g., sweet, dry/reinforced).

Since some years, the French wine sector faces strategical challenges, all linked to climate change. Multiple issues have been observed like diseases development, early frost, drought, change in the precocity and maturity of grapes, each one resulting in loss of productivity and yield. In France, the varieties proposed today by nurseries are historical varieties that are not well adapted to those changes. Therefore, Mercier Frères, one of the leading grapevine nursery, has decided to start its own research programs, with the help of its laboratory Novatech, to answer the growing demand for new grapevine varieties.

The main objective of this study was to establish if beet sugar produces a different concentration of “fruity” volatile aroma compounds (VOCs), compared to cane sugar when used for second alcoholic fermentation of Auxerrois sparkling wines. Auxerrois base wine from the 2020 vintage was separated into two lots; half was fermented with cane sugar and half with beet sugar (both sucrose products and tested for sugar purity). These sugars were used in yeast acclimation (IOC 2007), and base wines for the second fermentation (12 bottles each). Base wines were manually bottled at the Cool Climate Oenology and Viticulture Institute (CCOVI) research winery. The standard chemical analysis took place at intervals of 0, 4 weeks, and 8 weeks post-bottling. Acidity and pH measurements were carried out by an auto-titrator. Residual Sugar (g/L) (glucose (g/L), fructose (g/L)), YAN (mg N/L), malic acid, and acetic acid (g/L) were analyzed by Megazyme assay kits. parameters were analyzed by Megazyme assay kits. Alcohol (% v/v) was assessed by GC-FID. VOC analysis of base wines, finished sparkling wines, as well as the two sugars in model sparkling wine solutions, was carried out by GC-MS. VOCs included ethyl octanoate, ethyl hexanoate, ethyl butanoate, ethyl decanoate, ethyl-2-methylbutyrate, ethyl-3-methylbutyrate, ethyl 2-methyl propanoate, ethyl 2- hydroxy propanoate, 1-hexanol, 2-phenylethan-1-ol, ethyl acetate, hexyl acetate, isoamyl acetate and 2-phenylethyl acetate.

In recent studies, several grapevine trunk pathogen complexes have been identified from grapevines in South Africa. These pathogens include Eutypa lata, Phaeomoniella chlamydospora, Phaeoacremonium sp., Botryosphaeria sp. and Phomopsis sp. Trunk diseases lead to reduced yield, and grape quality as well as a decline