Laurence Geny-Denis

A six-year field study was conducted at Château Lafite Rothschild in Bordeaux, France, to investigate the effects of biodynamic (BD) preparations on soil microbiological and chemical properties. Basal respiration (B-Resp), microbial biomass carbon (MBC), total carbon (C-total), and soil organic carbon (SOC) were analyzed in soils from organically managed vineyards, comparing those without (BD −) and with BD preparations (BD +). Accordingly, two treatments were arranged in a randomized block design with four replicates. Soil microbial activity was assessed using the multi-substrate-induced respiration (multi-SIR) method, which measured the catabolic response to 17 low molecular weight organic substances (LMWOS). The results indicated that BD + plots exhibited significantly higher B-Resp (+ 40.0%) and MBC (+ 33.7%) compared to BD − plots, suggesting enhanced microbial metabolic activity. An upward trend in SOC (+ 17.4%) and C-total (+ 16.7%) was observed in BD + soils, indicating improved carbon sequestration potential. The multi-SIR analysis revealed a significant increase in respiratory responses to D-glucose and D-fructose in BD + plots, and an increasing trend of respiratory response for 13 other LMWOS. A higher respiratory response suggests a lower anabolic demand for specific substrates. Principal component analysis distinctively separated BD + from BD − treatments, underscoring the microbial functional profile changed by BD preparations. The significant increases observed in BD + treatments, particularly in B-Resp, MBC, and the catabolic use of D-glucose and D-fructose, demonstrate that integrating BD preparations into organic vineyard systems enhances the biological activity of microbial communities in soils. In the ongoing experiment further research will allow us to understand better longer-term impacts of BD on soil properties.

At a time marked by a transition in winegrowing methods, the decision to employ biodynamic viticulture, and its holistic approach, is a choice made by many technicians in the French wine industry. Nevertheless, this practice is perceived very differently among industry members. Some frequently debate its foundations and tangible benefits, while others question the value of scientific research conducted on its methods. The representations motivating the decision to pursue biodynamic practices remain unclear. Thirty members of the industry were interviewed about their opinions and knowledge on biodynamics through semi-structured interviews. A textual analysis of their responses, using Alceste software (Image Ltd., Toulouse, France, version 2018), revealed four key representations of this growing method within the industry. Some practitioners believe that biodynamic preparations may have a material effect on plant behaviour and that the effects of biodynamic viticulture on the final quality of wine should be studied more closely. Others suggest that the anthroposophical foundations of the method should be set aside to allow for its reinvention in a forward-looking manner. Lastly, experimental methods and peer-exchanges are considered essential to understanding the effects of this cultivation method in specific contexts and terroirs. These different viewpoints should be integrated to develop innovative and interesting applications for biodynamic farming methods.

Pruning experimental studies have been performed in different vineyards, in France, USA and Australia. This article investigates and models the effects of pruning quality on the installation of desiccation cones and wood necrotization. Two different modalities of pruning, short and high pruning, were performed at the same period each year on three cultivars in Bordeaux (Cabernet Sauvignon and Sauvignon Blanc) and Charente (Ugni Blanc) wine regions. In the short typ of pruning, the diaphragm was damaged but, in the high one, a 2–3 cm woody length was left immediately above the diaphragm. None of the three cultivars showed any correlation between necrosis length and spur diameter (R² < 0.1925). Analysis of the Ugni Blanc, 8 months after pruning, showed significantly more necrosis length (>60%) than either Cabernet Sauvignon (31–41%) or Sauvignon Blanc (25–55%). Desiccation cone necrotization rates also varied with the vintage, particularly for Ugni Blanc. 4 or 8 months after pruning, the newly-installed desiccation cones could then be analysed. High pruning stopped the desiccation cones at the diaphragm, which ensured that the sap flow path remained unaffected.

This work investigated the structural, biochemical, and molecular characteristics of grape skin cell wall during ripening, related to susceptibility to Botrytis cinerea. The comparative study between the two main grape cultivars in Champagne region, Pinot noir and Chardonnay, quantified: (1) the maturity and physical profile of grape skin; (2) the morphological characteristics; (3) soluble pectic polysaccharides located in grape skin cell walls; and (4) the gene expression of the two main degrading enzymes (VvPME1 and VvPG1) and PME activity. During the maturation period, the grape skins of the two cultivars appear different in their structure and composition. Chardonnay is characterized by higher relative humidity (RH) and level of VvPG1 expression, lower disease incidence and penetrometry values, and thicker cell walls than Pinot noir skins. Thus, the cell wall composition is sufficiently different between grape varieties from the same area to allow their discrimination and could be used to better manage the harvest date.

The acid component of grape berries, originating in the metabolism of malate and tartrate, the latter being less well-known than the former, is a key factor at play in the microbiological stability of wines destined for distillation. Grape acidity is increasingly affected by climate changes. The ability to compare two vintages with contrasted climatic conditions may contribute to a global understanding of the regulation of acid metabolism and the future consequences for berry composition. The results of the analyses (molecular, protein, enzymatic) of tartrate biosynthesis pathways were compared with the developmental accumulation of tartrate in Ugni blanc grape berries, from floral bud to maturity. The existence of two distinct steps during this pathway was confirmed: one prior to ascorbate, with phases of VvGME, VvVTC2, VvVTC4, VvL-GalDH, VvGLDH gene expression and abundant protein, different for each vintage; the other downstream of ascorbate, leading to the synthesis of tartrate with maximum VvL-IdnDH genetic and protein expression towards the beginning of the growth process, and in correlation with enzyme activity regardless of the vintage. Overall results suggest that the two steps of this pathway do not appear to be regulated in the same way and could both be activated very early on during berry development.