Comparison of tannin analysis by protein precipitation and normal-phase HPLC

The climate has warmed over the past century or more bringing about changes in numerous aspects in both earth and human systems

The spatial variability in soil type and depth and water holding capacity is very high in many viticultural regions of the world. Differences in rooting depths and water extraction profiles and their seasonal dynamics add additional variability and it is extremely difficult to deduct direct causal relationships between these factors and fruit

Red grapes contain significant amounts of phenolic compounds, known to contribute to wine quality and to provide important health benefits. Berry skin phenolics can be elicited by plant hormones. The aim of this work was to increase the content of anthocyanins and trans-resveratrol in five red varieties cultured in Argentina: Malbec (M), Bonarda (B), Syrah (S), Cabernet Sauvignon (CS), and Pinot Noir (PN), in two different growing regions: Santa Rosa (SR) and Valle de Uco (VU), by applying a post-veraison hormonal treatment with abscisic acid (ABA) and methyl jasmonate (MeJA).

Under-vine (UV) management has traditionally consisted of synthetic herbicide use to limit competition between weeds and grapevines. With growing global interest towards non-synthetic chemical use, this study aimed to capture the effects of alternative UV management at two commercial Shiraz vineyards in South Australia, where the sole management variables were UV management since 2016. In adjacent treatment blocks, cultivation (CU) was compared to spontaneous vegetation (SV) in McLaren Vale (MV), and herbicide was compared to SV in Eden Valley (EV). Soil water infiltration rates were slower and grapevine stem water potential was lower in CU compared to SV in MV, with the latter having a plant community dominated by soursob (Oxalis pes-caprae) during winter; while in EV, there was little separation between the treatments. Yields were affected at both sites, with SV being higher in MV and HE being higher in EV. In MV, the only effect on grape must was a lower 13C:12C isotope ratio in CU, indicating greater grapevine water stress. In the grape must at EV, SV had higher total soluble solids, total phenolics, anthocyanins, and yeast available nitrogen; and lower pH and titratable acidity. Pruning weights were not affected by the treatments in MV, while they were higher in HE at EV. Assessments revealed that the differing soil types at the two sites were likely the main determinants of the opposing production outcomes associated with UV management. In the silty loam soil of MV, the higher yields in SV were likely due to more plant-available water, as a potential result of the continuous soil bio-pores formed by winter UV vegetation. Conversely, in the loamy sand soils of EV with a lower cation exchange capacity, the lower yields and pruning weights in SV suggest the UV vegetation competed significantly with the grapevines for available water and nutrients.

Climate change is impacting wine production in all parts of the world in highly variable ways that may change the expression of terroir, from rapid loss of viability right through to highly beneficial aspects that increase suitability