Diego S. Intrigliolo

Effects of cluster light exposure on 3-isobutyl-2-methoxypyrazine accumulation and degradation patterns in red wine grapes ( Vitis vinifera L. Cv. Cabernet Franc).

The effects of light exposure on 3-isobutyl-2-methoxypyrazine (IBMP) accumulation and degradation in Vitis vinifera L. cv. Cabernet Franc berries were assessed by comparison of shaded and exposed clusters within the same vine throughout a growing season. Twenty-seven vines were shoot-thinned to create regions of high and low cluster-light exposure within each vine. Samples were collected at 10 time points starting from 5 to 130 days postbloom. The experimental design allowed for intravine comparison of IBMP levels between treatments at each time. Vine-to-vine variability of IBMP and the correlation of IBMP to malic acid were also evaluated. Cluster exposure reduced accumulation of IBMP at all preveraison time points by 21-44%, but did not increase postveraison degradation. Significant vine-to-vine variability in IBMP content was observed, with the highest level of IBMP in shaded berries in the most vigorous block of vines. Although IBMP concentration by weight decreased significantly due to dilution just prior to color change (veraison), no significant IBMP degradation per berry occurred until after color change (day 70 postbloom). By contrast, malic acid degradation began prior to color change, and malic acid concentrations were not affected by cluster exposure preveraison, but were affected postveraison. A survey of 13 sites in New York state (Seneca Lake) showed that IBMP concentrations at 2 weeks preveraison were highly correlated (R(2) = 0.936, p < 0.0001) to levels at harvest, whereas classic grape maturity indices at harvest were uncorrelated with IBMP at harvest. In summary, light exposure conditions critically influence IBMP accumulation but not IBMP degradation.

Response of grapevine cv. ‘Tempranillo’ to timing and amount of irrigation: water relations, vine growth, yield and berry and wine composition

The effects of several moderate irrigation regimes on vine water status, yield, and must and wine composition, were investigated during five seasons in a vineyard planted with Vitis vinifera cv. Tempranillo. Treatments consisted of non-irrigated vines and six differentially irrigated treatments with contrasting watering regimes during the pre-veraison and post-veraison periods. There were large differences in yield and grape and wine quality responses to irrigation among seasons, probably as consequence of the different environmental conditions and crop levels. It was, however, clear that vines benefit more of the irrigation supplied in years of high yield levels. Across seasons, yield increased in proportion to the amount of water applied mostly due to the larger berries of irrigated vines, and there was no clear response to the timing of irrigation supplied. In addition, there were no carry over effects due to irrigation on bud fertility. The post-veraison water application was necessary to increase must sugar level and wine alcohol content. However, water restrictions during the pre-veraison period lead to more concentrated berries in terms of total phenolic and anthocyanins. The only noticeable detrimental effect of irrigation, regardless of the timing of its application, on wine composition was an increase in wine pH.

Unmixing-Based Fusion of Hyperspatial and Hyperspectral Airborne Imagery for Early Detection of Vegetation Stress

Many applications require a timely acquisition of high spatial and spectral resolution remote sensing data. This is often not achievable since spaceborne remote sensing instruments face a tradeoff between spatial and spectral resolution, while airborne sensors mounted on a manned aircraft are too expensive to acquire a high temporal resolution. This gap between information needs and data availability inspires research on using Remotely Piloted Aircraft Systems (RPAS) to capture the desired high spectral and spatial information, furthermore providing temporal flexibility. Present hyperspectral imagers on board lightweight RPAS are still rare, due to the operational complexity, sensor weight, and instability. This paper looks into the use of a hyperspectral-hyperspatial fusion technique for an improved biophysical parameter retrieval and physiological assessment in agricultural crops. First, a biophysical parameter extraction study is performed on a simulated citrus orchard. Subsequently, the unmixing-based fusion is applied on a real test case in commercial citrus orchards with discontinuous canopies, in which a more efficient and accurate estimation of water stress is achieved by fusing thermal hyperspatial and hyperspectral (APEX) imagery. Narrowband reflectance indices that have proven their effectiveness as previsual indicators of water stress, such as the Photochemical Reflectance Index (PRI), show a significant increase in tree water-stress detection when applied on the fused dataset compared to the original hyperspectral APEX dataset (R2 = 0.62, p <;0.001 vs. R2 = 0.21, p > 0.1). Maximal R2 values of 0.93 and 0.86 are obtained by a linear relationship between the vegetation index and the resp., water and chlorophyll, parameter content maps.

Effects of preflowering leaf removal on phenolic composition of tempranillo in the semiarid terroir of Western Spain

The effects of preflowering defoliation on the qualitative and quantitative composition of phenolic compounds in the grape skins of Tempranillo grapevines grown in a semiarid terroir of western Spain, Badajoz, were determined. Control vines were compared with defoliation carried out before flowering (ED) in 2009 and 2010. Forty-two phenolic compounds were identified and quantified in the grape skins, including anthocyanins, flavonols, flavanols (cathechin and epi-cathechin and the flavanol dimmers B1, B2, and B3), and hydroxycinnamic acids, as both simple and conjugated molecules. ED did not significantly alter the concentration of total anthocyanidins, although in 2009, 3-O-acylated monoglucosides and p-coumaroylglucoside forms were more abundant in this treatment. A nonsignificant tendency toward increased total flavanols due to defoliation treatment was observed. Leaf removal increased concentrations of flavonols (glycosides of myricetin, quercetin, kaempherol, and isorhamnetin), hydroxycinnamic acids, and stilbenes in season-specific ways. Preflowering leaf removal may contribute to increased concentrations of compounds that can form complexes with anthocyanins (copigments) and may thus improve wine color stability.

Interactive Effects of Irrigation and Crop Level on Tempranillo Vines in a Semiarid Climate

The effects of different irrigation and crop level regimes on performance of Tempranillo vines in a Mediterranean climate were studied under field conditions over a 4-year period (2005 to 2008). Vines were subjected to irrigation treatments that provided 100, 50, or 25% of crop evapotranspiration (ETc) or to a dry-farmed regime. Two crop levels (high and low) established by veraison cluster thinning were studied for each of the treatments. Increased irrigation doses resulted in higher yield and vine growth, although the 25% ETc treatment showed the highest irrigation water use efficiency, with yields similar to the 50% ETc treatment. The short- and long-term (next crop season) effects of the treatments on vegetative and productive parameters (i.e., leaf area index and cluster weight) were related to vine water status, especially in relation to the preveraison period. Irrigation increased must titratable acidity (TA) but did not affect total soluble solids or pH. Cluster thinning resulted in a higher leaf area-to-yield ratio and lower yield even though a compensatory increase in cluster weight was observed in the low crop level treatments. For similar Brix, cluster thinning decreased TA and increased must pH, a negative result because must pH values in the study region are generally too high. Irrigation at 25% of ETc can be considered a good strategy for increasing yield compared to dry-farmed vines while also maximizing water use efficiency without compromising grape composition.

Assessment of a Remote Sensing Energy Balance Methodology (SEBAL) Using Different Interpolation Methods to Determine Evapotranspiration in a Citrus Orchard

A surface energy balance algorithm for land (SEBAL) for estimating evapotranspiration (ET) has been parameterized and tested in a 400-ha drip irrigated citrus orchard. Simultaneously, during three growing seasons, energy fluxes were measured using Eddy Covariance. Instantaneous fluxes obtained with SEBAL using 10 images from Landsat-5 were compared with the measured fluxes. The Perrier function was the best method for properly estimating the roughness momentum length for discontinuous canopies, as in citrus orchards. Crop height was estimated using LIDAR data. In general, SEBAL performed well for net radiation estimation but failed in soil heat flux estimation. Latent heat estimations from the SEBAL model had a relative root mean square error (rRMSE) of 0.06 when compared with measurements obtained by Eddy Covariance. Three procedures were tested for up-scaling the instantaneous ET estimates from SEBAL to daily ET values: 1) assuming the fraction between the actual ET and the reference ET is constant throughout the day; 2) using actual local crop coefficient curves; and 3) using an up-scaling factor where the fraction of hourly ET to daily ET equals the ratio of hourly to daily global solar radiation. This last method gave acceptable results for daily ET estimations (rRMSE = 0.09) and for 15day ET (rRMSE = 0.19), and its main advantage is that no local data are required. It is concluded that the SEBAL methodology can be successfully applied for determining actual ET, even in discontinuous citrus canopies. However, additional parameterizations of momentum roughness length were needed in order to obtain reliable ET determinations.

Grape Composition under Abiotic Constrains: Water Stress and Salinity

Water stress and increasing soil salt concentration represent the most common abiotic constrains that exert a negative impact on Mediterranean vineyards performance. However, several studies have proven that deficit irrigation strategies are able to improve grape composition. In contrast, irrigation with saline waters negatively affected yield and grape composition, although the magnitude of these effects depended on the cultivar, rootstock, phenological stage when water was applied, as well as on the salt concentration in the irrigation water. In this context, agronomic practices that minimize these effects on berry composition and, consequently, on wine quality must be achieved. In this paper, we briefly reviewed the main findings obtained regarding the effects of deficit irrigation strategies, as well as irrigation with saline water, on the berry composition of both red and white cultivars, as well as on the final wine. A meta-analysis was performed using published data for red and white varieties; a general liner model accounting for the effects of cultivar, rootstock, and midday stem water potential was able to explain up to 90% of the variability in the dataset, depending on the selected variable. In both red and white cultivars, berry weight, must titratable acidity and pH were fairly well simulated, whereas the goodness-of-fit for wine attributes was better for white cultivars.

Water Versus Source–Sink Relationships in a Semiarid Tempranillo Vineyard: Vine Performance and Fruit Composition

Grapevine yield and fruit composition largely depend on vine water status, which can be manipulated, especially in semiarid climates, by irrigation strategies and training systems. The objective of this research was to examine the influence of canopy height on vine growth, yield, and berry traits of Tempranillo vines under different degrees of water stress. Two canopy heights and three irrigation strategies, similarly applied in the two training systems, were tested in combination. Over two years (2010 and 2011), elevating the canopy resulted in a 26% increase in leaf area per vine but also in greater water stress. As a consequence, yield was reduced by an average of 12% in the elevated canopy for the three irrigation levels, due to lower cluster and berry weight; berries from the elevated canopy had greater total soluble solids and anthocyanin concentrations, lower total acidity, and lower malic and tartaric acid concentrations. There were only slight differences in yield under the different irrigation regimes. However, berry anthocyanin concentrations were higher when an early deficit irrigation strategy was applied. Midday stem water potential, rather than the leaf-area-to-yield ratio, better explained differences in vine performance and fruit composition between the treatments. This suggests that vine performance in the study area is more influenced by water availability than by the amount of sunlight intercepted.

Chloride stress triggers maturation and negatively affects the postharvest quality of persimmon fruit. Involvement of calyx ethylene production.

In recent years many hectares planted with persimmon trees in E Spain have been diagnosed with chloride toxicity. An effect of this abiotic stress on fruit quality has been reported in different crops. However, the impact of chloride stress on persimmon fruit quality is unknown. The harvest and postharvest quality of persimmons harvested from trees that manifest different intensities of chloride toxicity foliar symptoms was evaluated herein. Our results revealed that fruits from trees under chloride stress conditions underwent chloride accumulation in the calyx, which was more marked the greater the salt stress intensity trees were exposed to. Increased chloride concentrations in the calyx stimulated ethylene production in this tissue. In the fruits affected by slight and moderate chloride stress, calyx ethylene production accelerated the maturity process, as reflected by increased fruit colour and diminished fruit firmness. In the fruits under severe chloride stress, the high ethylene levels in the calyx triggered autocatalytic ethylene production in other fruit tissues, which led fruit maturity to drastically advance. In these fruits effectiveness of CO2 deastringency treatment was not complete and fruit softening enhanced during the postharvest period. Moreover, chloride stress conditions had a marked effect on reducing fruit weight, even in slightly stressed trees.

Assessment of drip irrigation sub-units using airborne thermal imagery acquired with an Unmanned Aerial Vehicle (UAV)

The proper maintenance of irrigation sub-units is a key aspect for efficient irrigation and for ensuring that the theoretical high drip irrigation application efficiencies are achieved. The performance assessment methods are based on the discharge measurements of some emitters sampled within the irrigation unit. The emitter selection is a key aspect for guaranteeing that plot heterogeneity is well represented. In this work, thermal images obtained by means of an Unmanned Aerial Vehicle over an irrigation district were used to determine irrigation performance. Four irrigation sub-units were assessed with standard methods. Canopy temperature showed a good correlation with the total flow discharge when plant water status variability in the sub-unit was high. When standard irrigation performance assessment protocols are used, the sample of emitters is small and so the large existing variability might not be taken into account. Aerial thermal images can quantify plant water status in large areas enabling the detection of some failures in the irrigation delivery system that might not be always detected with the standard irrigation performance assessment protocols.