C. Acevedo-Opazo

Gas exchange relations of ungrafted grapevines (cv. Carménère) growing under irrigated field conditions

A study was carried out to evaluate the leaf gas exchange relations and water-use efficiency (WUE) of ungrafted Carmenere (Vitis vinifera L.) grapevines growing under field conditions and different levels of water stress. Stomatal conductance (g s ), transpiration (E), net CO 2 assimilation (A N ) and stem water potential (Ψs) were measured at midday in a drip-irrigated commercial vineyard located in the Maule Valley (Chile) during three growing seasons (2005 to 2009). In addition, the instantaneous (A N /E) and intrinsic (A N /g s ) water-use efficiencies and stomatal sensitivity factor (k) were estimated for the own-rooted grapevines. In this study a significant non-linear relationship was observed between A N and g s (r 2 = 0.82), with values of A N decreasing from 14.9 to 3.5 μmol/m 2/ sec as g s diminished from 0.5 to 0.05 mol/m 2 /sec. This resulted in a progressive increase in WUEi (intrinsic water use efficiency). A significant linear relationship was observed between Ψs and g s (r 2 = 0.39) for measurements taken before and after veraison, with an increasing scattering from -1.6 to -0.4 MPa. Finally, k decreased as water stress increased, with values of 234 and 120 for no and severe water stress respectively, while k ranged from 264 to 480 and 255 to 297 for the measurements taken before and after veraison respectively. Based on the results obtained in the present study, the cultivar Carmenere could be classified as drought tolerant at low water potentials, with a large range of physiological parameters changing in response to water stress.

Evaluation of a decision support strategy for the control of powdery mildew, Erysiphe necator (Schw.) Burr., in grapevine in the central region of Chile

BACKGROUND The primary strategy to control powdery mildew in Chilean vineyards involves periodic fungicide spraying, which may lead to many environmental and human health risks. This study aimed to implement and evaluate the effectiveness and economic feasibility of a novel decision support strategy (DSS) to limit the number of treatments against this pathogen. An experiment was conducted between the 2010 and 2013 seasons in two irrigated vine fields, one containing a cultivar of Cabernet Sauvignon (CS) and the other a cultivar of Chardonnay (CH). RESULTS The results showed that the DSS effectively controlled powdery mildew in CS and CH vine fields, as evidenced by a disease severity lower than 3%, which was lower than that observed in untreated vines (approximately 10 and 40% for CS and CH respectively). The DS strategy required the application of only 2-3 fungicide treatments per season in key vine phenological stages, and the cost fluctuated between

Using ancillary yield data to improve sampling and grape yield estimation of the current season

US 322 and 415 ha-1 , which was 40-60% cheaper than the traditional strategy employed by vine growers. CONCLUSION The decision support strategy evaluated in this trial allows a good control of powdery mildew for various types of epidemic with an early and late initiation.

Classification of winegrape cultivars in Chile and France according to their susceptibility to Botrytis cinerea related to fruit maturity

This paper proposes a methodology aiming at using historical yield data to improve yield sampling and yield estimation. The sampling method is based on a collaboration between historical data (at least three years) and yield measurements of the year performed on some sites within the field. It assumes a temporal stability of within field yield spatial patterns over the years. The first factor of a principal component analysis (PCA) is used to summarize the stable temporal patterns of within field yield data and it represents a large part of the variability of the different years assuming yield temporal stability and a high positive correlation between this factor and the yield. This main factor is then used to choose the best sites to sample (target sampling). Yield measurements are then used to calibrate a model that relates yield values to coordinates on the first factor of the PCA. This sampling method was tested on three vine fields (Vitis vinifera L.) in Chile and France with different varieties (Chardonnay, Cabernet Sauvignon and Syrah). For each of these fields, yield data of several years were available at the within field level. After temporal stability of yield patterns was verified for almost all the fields, the proposed sampling method was applied. Results were compared to those of a classical random sampling method showing that the use of historical yield data allows sampling sites selection to be optimized. Errors in yield estimations were reduced by more than 10% in all the cases, except when yield stable patterns are affected by specific events, i.e. early frost occurring on Chardonnay field.

Assessment of an empirical spatio-temporal model of the grapevine phenology at the within-field scale

Background and Aims The susceptibility of winegrape cultivars to Botrytis cinerea is a debated topic, and the available classifications are based on professional experience rather than on experimental data. The main aim of this study was to compare and classify the susceptibility of several winegrape cultivars to B. cinerea and its relation to fruit maturity under two contrasting climatic and cropping conditions. Methods and Results Between 2011 and 2015, three field trials were undertaken in Chile and France, including 13 common cultivars. Both the incidence and severity of the disease were evaluated at harvest, and indices of susceptibility and maturity were calculated on a per site basis. The significant difference in incidence and severity observed among cultivars led to a similar susceptibility classification in both countries. Cabernet Sauvignon, Cabernet Franc, Grenache Noir and Petit Verdot were the most resistant cultivars, whereas Gewurztraminer and Sauvignon Blanc were the most susceptible. Moreover, an exponential and positive relationship was established between indexes of susceptibility and maturity. Conclusions The classification of cultivars according to the susceptibility to B. cinerea was similar in both countries, despite the contrasting climatic conditions and cropping practices. Significance of the Study These findings might be of interest for choosing cultivars that are more resistant to B. cinerea to reduce the number of fungicide applications.

The potential of high spatial resolution information to define within-vineyard zones related to vine water status

The aim of this work is to calibrate and validate an empirical approach to predict the date of occurrence of the grapevine phenology (budburst, flowering and veraison) temporally and spatially at the within-field scale. It is based on the collaboration between a classical model of phenology based on climate data and a spatial model calibrated with ancillary data of phenology observations. This approach was tested and validated on a field of cv Cabernet Sauvignon. Results showed that the spatial component improved the fit of the climatic model, allowing the generation of maps of the grapevine phenology with errors lower than 5 days of prediction. Spatio-temporal model errors were mainly associated with the temporal component of the model.