Browsing by Author "Verdugo-Vasquez, Nicolas"

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    Sunscreen Based on Dicarboxylic Acid Salts Applications to Blueberries (Vaccinium corymbosum L.) Plants: Effects on Water Stress Tolerance and Productivity
    (2022) Gutierrez-Gamboa, Gaston; Guerrero-Mendez, Mario; Araya-Alman, Miguel; Verdugo-Vasquez, Nicolas; Valdes-Gomez, Hector; Acevedo-Opazo, Cesar
    Background: Recently, antitranspirant or radiation-reflective products have been studied in several crops to mitigate the negative effects of global warming in Mediterranean climates. Nevertheless, to our knowledge, there is a scarce availability of information studying their effects on blueberries and much less from applications of sunscreens elaborated based on a mixture of dicarboxylic acids. Methods: Controls and three treatments were performed in 'Duke' and 'Star' blueberries as follows: (i) control without water stress (T1 = 100% ETc); (ii) foliar application of sunscreen in plants without water stress (T2 = 100% ETc + sunscreen); (iii) water stress in plants without foliar application of sunscreen (T3 = 50% ETc); (iv) foliar application of the sunscreen in plants with water stress (T4 = 50% ETc + sunscreen). Stem water potential (Psi s), stomatal conductance (g(s)), yield, berry weight and berry total soluble solids were determined. (3) Results: As expected, the decrease in irrigation frequency in water stress treatments (T3 and T4) allowed for a decrease in the water applied at 25% compared to non-stressed plants (T1 and T2). This resulted in an increase in the Psi s on the days closest to harvest in both varieties, decreasing g(s) in blueberries plants subjected to water stress conditions. Sunscreen applications to Duke plants subjected to water stress (T4) induced higher total berry soluble solids than the treatments performed in non-stressed plants (T1 and T2). Sunscreen applications to Star plants subjected to water stress (T4) promoted similar g(s) levels and did not affect total soluble solids concerning irrigated plants (T1 and T2). (4) Conclusions: The results suggest that the response to water stress to sunscreen application based on dicarboxylic acid salts depended on the cultivar. Therefore, despite the novelty of this research, it is necessary to perform long-term studies to establish accurate conclusions.
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    Vigor thresholded NDVI is a key early risk indicator of Botrytis bunch rot in vineyards
    (2020) Panitrur-De la Fuente, Carolina; Valdes-Gomez, Hector; Roudet, Jean; Verdugo-Vasquez, Nicolas; Mirabal, Y.; Laurie, V. F.; Goutouly, Jean-Pascal; Acevedo-Opazo, Cesar; Fermaud, Marc
    Botrytis bunch rot (BBR) is a major disease occurring in vineyards worldwide. Its control is still largely based on the use of synthetic fungicide sprayings at predetermined intervals, which often produces negative residues in grapes and wines that may affect the environment and/or human health. To rationalize BBR management, disease risk indicators were developed and evaluated in a set of field experiments carried out between 2010 and 2019 in France and Chile. Key indicators include early grapevine vegetative growth, i.e. ground-based normalized difference vegetation index (NDVI), and the potential berry susceptibility to Botrytis cinerea, which is driven by tannin content in the skin. Under these contrasting weather and cropping conditions, regression analyses, including weather information, showed a highly significant positive correlation between the early NDVI, measured at berry pea size stage, and BBR incidence or severity at harvest, whereas the opposite was demonstrated for tannin content in the berry skin measured at an early herbaceous fruit stage. The exponential relationship between the final disease severity and the early NDVI allowed us to identify a possible threshold NDVI value, i.e. between 0.5 and 0.6, under which the BBR severity should be lower or close to 5% at harvest (BBR tolerance threshold for wine quality). Accordingly, in a leaf-removal vineyard experiment in France, the NDVI level at berry pea size stage was strictly controlled to correspond to three different increasing index values: 0.45, 0.60, and 0.78. Following this increase in NDVI, a significant increase in final BBR severity was noticeable, i.e. 2.4%, 6.6% and 9.9%, respectively. Very interestingly, the NDVI increase was also related to a significant decrease in the tannin content in the skin of herbaceous berries at veraison, from 47 to 22 mg tannin/g skin. All regression analyses explaining BBR development were highly significant, showing the weather conditions before harvest as the primary factor. They also show that some of the disease risk indicators chosen, especially early NDVI, could be used in the future as tools in decision support systems for deciding to spray and/or scheduling optimized fungicide applications during the season.