Effect of soil particle size on vine water status, leaf ABA content and berry quality in Nebbiolo grapes

Abstract

The root and shoot abscisic acid (ABA) accumulation in response to water deficit and its relation with stomatal conductance is longtime known in grapevine. ABA-dependent and ABA-independent signalling response to osmotic stress coexist in sessile plants. In grapevine, the signaling role of ABA in response to water stress conditions and its influence on berry quality is critical to manage grapevine acclimation to climate change. The prevalent iso- or aniso-hydric behavior of grapevine varieties can be mitigated by the soil draining capacity: in the anisohydric Syrah grown in pots and in controlled conditions, an ABA-related stomatal closure was induced in water-retaining soils, resulting in a superimposition of the soil-related hormonal root-to-shoot signal respect to the putative genotypic-induced anisohydric response to water stress. In two consecutive years (2012 and 2013) we analyzed Nebbiolo water relations in two rain-fed vineyards (distance as the crow flies between the two was about 250 m) located on the Cannubi hill (Barolo area, Langhe Wine District, Piedmont, Italy). Vines were grafted on Vitis berlandieri x V. riparia rootstocks and soil were classified (USDA) as silty-loam (with 18 % of clay) and as loam (13 % of clay). We measured stomatal conductance, stem water potential, ABA leaf content and the main berry quality parameters. In 2013, the vineyard management (winter and green pruning, and bunch balance according to ‘Yield to Pruning Weight’ and ‘Leaf Area to Crop Weight’ ratios) allowed to avoid any discrepancies in the two vineyards vegetative-productive balance. Data showed that when drought was prolonged, Nebbiolo reduced its anisohydricity acting drought-induced stomatal closures earlier and for a longer period in the silty-loam soil, (richer in clay and more compact), respect to the loamy soil. The silty-loam soil determined a higher leaf ABA content during the season. This fact could explain the improved qualitative traits of berries harvested in the vineyard in the 18% clayey soil such as a higher content of anthocyanins (mg/berry), with a higher level of acylation (increase of color stabilization) and a higher content of free terpenes, following ABA-triggered metabolite responses.

Acknowledgements: authors warmly acknowledge Damilano cellar for hosting the trial.