Mechanisms responsible for different susceptibility of grapevine varieties to flavescence dorée

Despite the extensive research performed during the last decades, the multifactorial mechanism responsible for the white wine protein haze formation is not fully characterized. Herein, a new model is proposed, which is based on the experimental identification of sulfur dioxide as a major modulating factor inducing wine protein haze upon heating. As opposed to other reducing agents, such as 2-mercaptoethanol, dithiothreitol and tris(2-carboxyethyl)phosphine hydrochloride (TCEP), the addition of SO2 to must/wine upon heating cleaves intraprotein disulfide bonds, hinders thiol-disulfide exchange during protein interactions and can lead to the formation of novel inter/intraprotein disulfide bonds. Those are eventually responsible for wine protein aggregation which follows a nucleation-growth kinetic model as shown by dynamic light scattering [1].

Temperature is a relevant parameter during vineyard development, affecting vine phenology and grape maturity. Moreover, the climate of the different Chilean valleys influences the varieties cultivated, the ripening period and the final quality of the wines. The use of growing degree days (GDD) is known worldwide for the study of climate in viticulture regions. However, little is known about the evolution of maturity and the sugar loading stop, based on this parameter.

Copper in white wine can be associated with Cu(II) organic acids (Cu fraction I), Cu(I) thiol species (Cu fraction II), and Cu sulfides (Cu fraction III). The first two fractions are associated with the repression of reductive aromas in white wine, but these fractions gradually decrease in concentration during the normal bottle aging of wine. Although exposure of white wine to fluorescent light is known to induce the accumulation of volatile sulfur compounds, causing light-struck aroma, the influence on the loss of protective Cu fractions is uncertain. Riboflavin is known to be a critical initiator of photochemical reac-tions in wine, but the rate of its decay under short-term light exposure in different coloured bottles and for wine of different oxygen concentrations is not well understood.

In recent years, a pool of terpenoids possibly implicated in minty odours and in the appreciable refreshing sensation, has been identified in long aged red Bordeaux wines (Lisanti et al., 2021, Picard et al., 2016; Picard et al., 2017). These compounds were found to play a key role in the so-called “ageing bouquet”, that can be defined as “the homogeneous, harmonious flavour resulting from the complex transformation process in wine during bottle storage” (Picard et al., 2015). Moreover the minty-fresh sensory dimension in fine aged red wines plays an important role in typicity judgement by wine professionals (Picard et al., 2015).

The decision for grape berries to ripen involves a complex interplay of genetic regulation and environmental cues. This review explores the molecular mechanisms underlying the transition from vegetative growth to ripening, focusing on transcriptomic studies and the role of the NAC gene family. Transcriptomic analyses reveal a significant rearrangement of gene expression patterns during this transition, with up-regulation of ripening-related genes and down-regulation of those associated with vegetative growth. A molecular phenology scale providing a high-precision map of berry transcriptomic development, indicates that key molecular changes occur well before the onset of ripening.