Sunburn and its Relation to Maturity and Concentration of Aromatic Compounds in Bush-Trained Muscat of Alexandria Vines

sun-burn


Introduction
Fresh fruit sunburn is a critical issue affecting the quality of horticultural commercial production.For instance, sunburn in apples can reduce marketable yield by as much as 20% (Wünsche et al. 2001).Recent technical reports claim that sunburn is the leading cause of apple "packouts," affecting more than 50% of harvested fruit in some years (Schmidt 2018).However, there is a lack of knowledge about the effect of sunburn on table and wine grape production (Greer and La Borde 2006).
The symptoms of sunburn in grape berries depend on several factors, such as variety, stage of development, and the presence of abiotic stress.Nevertheless, sunburn damage in grapevines exhibits clear physical symptoms in berry skins, which includes the degradation of chlorophyll and other photosynthetically active pigments (i.e., anthocyanins and carotenoids), the appearance of brown lesions, and the development of a shiny surface due to epicuticular wax crystalline structure losses (Greer et al. 2006).Moreover, sunburn-induced damage to the skin may increase the risk of berry dehydration due to a greater permeability of the cuticle to water loss (Bondada and Keller 2012).
From a commercial perspective, sunburn reduces the cosmetic value of berries, which may affect the vineyard's profitability.In Australia, winegrapes can be categorized as low-quality fruit if sunburn damage is identified in the winery (Gambetta et al. 2021).Although there is a lack of information about the effect of sunburn on wine quality, some markets consider the presence and severity of sunburn damage in the fruit to be a relevant defect.In Chardonnay, wines made with berries affected by sunburn tended to be more bitter, darker, and slightly less aromatic than those made with healthy berries, but no chemical analyses were provided (Greer and La Borde 2006).Traditionally, the presence of sunburn in fruits has been associated with air temperatures above 40°C.
Ibarra I et al.
Sunburn Impact on Fruit Quality However, recent studies have detected the appearance of sunburn lesions in berry skins from clusters exposed for five hours to air temperatures from 24 to 30°C and to solar radiation levels ~2.7 MJ/m 2 hr (Rustioni et al. 2014).These results indicate that berry sunburn can be induced at ambient temperatures considerably lower than those usually thought (Greer and Weedon 2013).
The interaction of the physiological, morphological, and biochemical characteristics of the fruit with the phenological stage, cultivar, and adaptability to environmental conditions determines the incidence and severity of sunburn damage in berries (Gambetta et al. 2021).Highlighting the role of fruit exposure to sunlight as a key determinant of sunburn in grape berries, Chorti et al. (2010) reported that removing leaves from the fruit zone at fruit set resulted in the highest level of sunburn damage in berries (37.5% of sunburn damage).Fruit overexposure is more often found in low-vigor vines (Romboli et al. 2017) or when shoots are severely trimmed during ripening (Diago et al. 2012).
The Itata valley is one of the few wine regions in Chile where vines are bush-trained and not irrigated during the whole growing season (Serra et al. 2017).In the bush training system, vines are not arranged in a permanent support structure, and vegetation appears discontinuously along the row (Freeman et al. 1992).This cultural management may be a key factor in obtaining unique wines that are representative of the Itata region, as bush-trained Chenin blanc vines have been found to produce berries with high pH but low soluble solids concentration and titratable acidity (Reynolds and Vanden Heuvel 2009).Nevertheless, the bush training system may increase the risk of sunburn on berries because clusters are very close to the warm soil during ripening (Freeman et al. 1992).Muscat of Alexandria is one of the most important cultivars in the Itata valley, accounting for >80% of the total planted area in Chile (SAG 2021).Muscat of Alexandria wines exhibit very characteristic fruity and floral aromas due to high concentrations of terpenes such as linalool, geraniol, and nerol (Black et al. 2015).In the Itata valley, the bush-trained Muscat of Alexandria vines often show low vigor, and clusters are exposed to maximum daily temperatures as high as 35°C for several weeks (Pascual et al. 2017).As global warming models predict a drastic increase in air temperature (up to 4°C) and evapotranspiration in the Chilean central valley in the most pessimistic scenario (Bambach et al. 2021), Muscat of Alexandria vines (especially under dry-farmed conditions) may be more vulnerable to sunburn.Due to the lack of scientific evidence that sunburn damage affects the chemical composition of the berry, a study was conducted to physically and chemically characterize berry sunburn in traditionally-farmed Muscat of Alexandria vineyards, using skin color as an objective measure of sunburn severity.

Study site
Six commercial nonirrigated and bush-trained vineyards (Vitis vinifera L.) of cv.Muscat of Alexandria, each representative of the traditional viticultural management of the Itata valley (Serra et al. 2017), were selected in 2018 and 2019 from several locations in the Ñuble Region, Chile.Traditional viticultural management includes mechanical weeding, minimal agrochemical application, and hand pruning.Fruit quality determinations, including berry sunburn characterization, were carried out at two fruit zone height classes (high, in which the fruit zone was 50 cm from the soil; and low, in which the fruit zone was between 2 and 10 cm from the soil) (Figure 1).The sampled vineyard blocks were very small, covering an area between 0.01 and 0.08 ha.Vines were planted at various spacing in different years, and all were >50-years-old (Table 1).The soils of Itata valley are derived mainly from the Chilean Coastal Range, exhibiting clay textures with drainage limitations.The study area is characterized by a Mediterranean climate and corresponds to a warm temperate climate with winter rains (663.7 mm/year) and dry summers, according to Köppen's classification (Ciren 2019).Daily values of maximum air temperature, solar radiation, and minimum relative humidity were obtained from the Nueva Aldea weather station

Vegetation indices
Two vegetation indices (VI), the normalized difference vegetation index (NDVI) (Equation 1) and the enhanced vegetation index (EVI) (Equation 2), were chosen to estimate vineyard "greenness" at veraison (mid-January) and harvest (last week of March) each season.Satellite images were obtained from the Landsat 8 (30-m pixel) and processed using Google Earth (Gorelick et al. 2017).The atmospheric correction of the images was performed using a Level-1 precision processor, and each VI was calculated using the following equations:

Fruit characterization
The harvest time in each vineyard was determined when the average soluble solids concentration of a 200-berry sample reached between 21 and 23 Brix.One day before commercial harvest, all clusters (between 15 and 25 clusters per vine) were collected from three randomly selected vines per vineyard.Because the average vineyard size was less than 0.1 ha (328.3 m 2 ) (Table 1), the sampling protocol consisted of taking all clusters from at least 3% of the study vineyard, as suggested by Hamilton and Coombe (1992) for small vineyards (<1 ha).A variance component analysis for the concentration of soluble solids (i.e., the ripeness index used in this study) conducted one year prior to this work (2017) showed that the variability among clusters from the same vine was 144% higher than among vines from the same vineyard (data not shown), statistically justifying harvesting more clusters from the same vine rather than fewer clusters from a larger number of vines.Each cluster was counted and individually weighed using an analytical scale (2.0 kg ± 0.01 g) to obtain yield estimates.The yield per vine was calculated as the sum of all the cluster weights.A composite five-berry sample was manually taken from a top (two berries), middle (two berries), and bottom position (one berry) on each cluster (total of five berries per cluster) to estimate sunburn severity in berries based on a visual assessment of skin appearance, where 1 = healthy and green-colored berries; 2 = healthy and amber-colored berries; 3 = moderate damage with light brown lesions; 4 = severe damage with dark brown lesions; 5 = very severe damage with black lesions (Figure 2).The skin hue was measured in each sampled berry using a portable colorimeter (CR-10 Plus, Konica-Minolta).Color readings were carried out at the center of the skin lesion in berries visually affected by sunburn (sunburn severities 3, 4, and 5).After color determinations, the soluble solids concentration and berry size were measured in each berry with an optical refractometer (Atago Hand Refractometer, Atago) and a digital caliper, respectively.
Maximum chlorophyll fluorescence (Fm) was measured at harvest using a portable fluorimeter (Pocket Pea, Hansatech Instruments) in three berries per class of sunburn severity (n = 15).Fm was measured in berries covered with adapted fiberoptic probes and maintained in total darkness for 30 min.Fluorescence readings were made after exposing the berries to saturated light conditions (4000 µmol/m 2 sec for 0.8 sec).Measurements were made at the fruit center for healthy berries (severities 1 and 2) and at the center of the lesion for sunburn-damaged berries (severities 3, 4, and 5).
The determination of volatile aromatic compounds was performed for three classes of sunburn severity (1, 3, and 5) that were collected and kept at -20°C until chemical (Eq. 1) (Eq.2) analysis.For determination of volatile aromatic compounds, grapes were defrosted at ambient temperature for over 40 min, and the seeds were removed.Afterward, three grapes were crushed in a 50-mL Falcon tube using an Ultra-Tur-raxTM homogenizer for 1 min.Then, 3.75 g of the sample was placed in a 20-mL glass vial, and 3.75 of milliQ water and 10 μL of 4-methyl-2-pentanol (0.75 mg/L) (used as an internal standard) were added.For the extraction and analysis, the methodology employed in Ubeda et al. ( 2017) was followed.The extraction was carried out in an MPS Autosampler (Gerstel), incubating the vial for 20 min at 45°C with agitation at 500 rpm.Then, the selected solid-phase microextraction fiber was a 2-cm 50/30-μm carboxen/ divinylbenzene/polydimethylsiloxane (Supelco) placed into the headspace of the vial for 40 min.Afterward, the desorption was carried out in the injector in the splitless mode for 3 min with a transfer line temperature of 280°C.A 7890B Agilent gas chromatography system coupled to an Agilent 5977 quadrupole inert mass spectrometer with a DB Wax capillary column (60 m × 0.25 mm, 0.25 μm film thickness) (J&W Scientific) was used to perform the gas chromatography analysis.Helium was used as the carrier gas at a flow rate of 1 mL/min.The program of the oven was: 35°C for 1 min, followed by an increase to 130°C at 4.5°C/min with holding for 3 min, an increase to 180°C at 2.5°C/min, and then an increase to 230°C at 5°C/min with holding for 1 min.The electron ionization mass spectra were recorded in scan mode at 70 eV in the range of 35 to 300 amu.The mass spectrometry Chemstation software (Agilent Technologies) was used for the recording and processing of the data.Identification of the compounds was done by employing authentic standards when available, as well as by comparing the mass spectra obtained from each molecule with the reference spectra of the NIST 98 software library (only considering compounds identified with a match score >900%) and with the data from the literature.Compounds were treated as tentatively identified when they were only identified by the software.The data were expressed as the relative area with respect to 4-methyl-2-pentanol (internal standard).The relative concentration was calculated by dividing the peak area of the target ion of each compound by the peak area of the target ion of the internal standard (Ubeda et al. 2020).

Experimental design and statistical analysis
This study was replicated three times in each of two consecutive years (2018 and 2019) and analyzed as a completely randomized design, where each vineyard with a fruit zone height was considered a replicate.Each replicate was randomly selected from several bush-trained vineyards under dry-farmed conditions with high and low fruiting zones.Means of various fruit parameters were analyzed by analysis of variance (ANOVA), and differences (p < 0.05) were subjected to Fisher's least significant difference means separation test.All statistical procedures were carried out using SAS-Studio 9.4 software (SAS Institute, Inc.).

Results
At anthesis, solar radiation ranged between 15 and 20 MJ/ m 2 in both seasons (Figure 3A).Close to veraison, solar radiation reached the maximum seasonal levels of ~30 MJ/m 2 in both seasons.Thereafter, a progressive decrease in solar radiation was observed, reaching values similar to those measured at anthesis.Weekly averages of maximum air temperatures never exceeded 35°C, and reached the highest seasonal values around veraison (90 days after anthesis) (Figure 3B).From budbreak to harvest (October to March), there were 63 and 41 days with maximum air temperatures above 30°C in the first and second seasons, respectively.
Vines with high and low fruit zones exhibited similar VIs (EVI and NDVI near 0.6) between veraison and harvest.There was a slight decrease in both VIs during ripening (~10%), but differences were only detected in the second season (Table 2).There were no differences in yield per vine, number of clusters, and cluster weight between fruit zone heights (Table 3).Although the yield per vine was similar in both seasons, the cluster number was significantly lower in 2017.However, the cluster weight was 19% higher in 2017.All clusters were harvested near 21 Brix each season.Differences in fruit height did not lead to differences in soluble solids concentration, berry diameters, or skin hue.The polar diameter of the berry was slightly higher than the equatorial diameter (10%) in both seasons.The hue of berry skins was 29.2% higher in the first season (104.9 in 2017 and 74.17 in 2018).The average severity of berry sunburn was near 2.2 in both seasons, with similar levels of severity between fruit zone heights.The combined incidence of moderate and severe sunburn was nearly 40% in both seasons (Figure 4A and 4B).
There was a quadratic relationship between skin hue and soluble solids concentration (R 2 = 0.59, p < 0.05) in berries from clusters that exhibited various levels of sunburn incidence (Figure 5).The hue variation was not associated with changes in the soluble solids concentration for sunburned berries, regardless of the damage severity.By contrast, healthy berries showed higher total soluble solids (TSS) as the hue decreased.There was a strong linear relationship between the Fm and the color parameter hue (R 2 = 0.72; p < 0.0001) for berries that represented five visual categories of sunburn damage (Figure 6).Thus, the more severely damaged berries were associated with the lowest values of Fm and hue, while healthy berries exhibited higher values of Fm and hue.
No significant season-by-severity interaction was detected in the present study, which is why pooled data are presented for sunburn severities and seasons.The ANOVA showed no differences in the concentration of the analyzed volatile aromatic compounds among sunburn severities (Table 4).Total terpenes in berries affected by moderate sunburn were three-times higher than in "healthy" berries.A two-fold decrease in total terpenes was observed in severely sunburned berries compared with moderately sunburned berries.The total concentration of terpenes was two times higher in severely sunburned berries than in "healthy" berries.The orthogonal contrast analysis showed that the concentration of linalool in healthy green berries was 60% lower than in sunburned berries (Figure 7).The concentration of volatile aromatic compounds tended to be higher in 2019, but differences were only detected for linalool, geraniol, and trans-2-hexenal.Thus, the average concentration of these three compounds together in 2018 was five-times lower than in 2019 (17.5 versus 105.6 μg/L, respectively).The exception was the β-citronellol, which was 64% lower in 2019.

Discussion
Despite differences in fruit zone height, the concentration of soluble solids was similar for all vines, reaching a technical    Sunburn Impact on Fruit Quality maturity appropriate for producing dry white wines from the Muscat of Alexandria cultivar (~21 Brix).These results were somewhat unexpected because clusters at the low fruit zone were closer to the warm soil, which may have stimulated berry dehydration and TSS increase in bush-trained vines.In the Itata valley, Pascual et al. (2017) reported that clusters from bush-trained Muscat of Alexandria vines were exposed to high air temperatures (>30°C) at least 30% of the time during the growing season.The lack of differences in soluble solids concentration between fruit zone heights was also observed for the remaining fruit quality parameters and yield components.This indicated that fruit zone height had no effect on the reproductive growth behavior of bushtrained vines even under nonirrigated conditions.The high percentage of sunburn damage found in this work (>40%) supports the hypothesis that air temperatures <40°C may be sufficiently high to induce sunburn in grape berries, as the maximum air temperature in the study area was rarely >35°C.In the present study, maximum solar radiation exceeded 2.5 MJ/m 2 hr from anthesis to harvest (for ~125 days), whereas maximum air temperatures were >30°C later in the season from veraison to harvest (for ~50 days).This means that both air temperature and sunlight intensity were sufficiently high to induce sunburn only throughout the ripening period.During ripening, grape berries have almost no evaporative cooling, as fruit transpiration rates are the lowest of the season (Greenspan et al. 1996).Clusters directly exposed to solar radiation can be several degrees above the air temperature (as much as 12°C) (Spayd et al. 2002).In low-vigor vines, fruit is usually overexposed to environmental conditions, and sunburn damage in berries is frequently found at harvest (Romboli et al. 2017).In general, the Muscat of Alexandria vines from the Itata valley exhibit small canopies and low interception ratios of solar radiation at the fruit zone (~50% of ambient photosynthetic photon flux density at 30 cm above the ground) (Pascual et al. 2017).
In the present study, pruning weights averaged ~0.4 kg/ vine (data not shown), which is 70% lower than those registered in moderately vigorous vines from the Itata valley Table 4 Main and total volatile compounds concentration at harvest in berries from bush-trained Muscat of Alexandria vines under nonirrigated conditions in the Itata valley, Chile.Sampled berries were visually categorized by sunburn severity (healthy, berries without lesions; moderate, faint reddish-brown lesions; severe, clear brown lesions).Data are expressed in relative area (abundance) with respect to the internal standard.a Different letters indicate significant differences between columns at 95% confidence level (least significant difference).n = 6.( Hidalgo et al. 2017).The study found a consistent reduction in the VIs tested in this study (EVI and NDVI) between veraison and harvest, reflecting a progressive decline in variables that are related to fruit exposure, such as canopy density and plant water status.NDVI and EVI have been correlated with leaf area index (Kang et al. 2022) and midday stem water potential (Helman et al. 2018).However, the lowest values of both VIs were only representative of moderate levels of abiotic stress in grapevine, which explains why, in this study, vines exhibited high yield components for bushtrained vineyards (Baeza et al. 1999) and Muscat of Alexandria vines (Avilez Cofré 2005).

Healthy
The visual assessment of sunburn severity used in this study based on the physical appearance of skin lesions reflected physical and biochemical changes associated with the effect of environmental stress conditions and fruit ripening.The linear regression analysis indicated that more severe levels of sunburn induced changes in skin hue that were related to reductions in chlorophyll fluorescence, measured as Fm.In grape berries, severe oxidative stress can generate irreversible damage in skin chloroplasts, causing chlorophyll degradation and hence, lower emission of fluorescence (Müller et al. 2001, Rustioni et al. 2014).However, the Fm values measured in this study were considerably lower than those previously reported for sunburn in grape berries (Greer et al. 2006) and other fruit crops (Wünsche et al. 2001).This finding indicates that fruit from the Itata valley was probably exposed to particularly high levels of oxidative stress, which may explain the higher percentage of sunburn damage (~40%) compared with previous studies (e.g., Greer et al. [2006] found sunburn damage percentages of 5 to 15% for Chardonnay vines in Wagga Wagga, Australia).
The regression analysis between skin hue and soluble solids concentration showed that sunburn-affected berries tended to exhibit higher TSS than healthy berries, which corresponds with the common belief that the occurrence of sunburn accelerates maturity.It has been suggested that the loss of the crystalline structure of the epicuticular wax of sunburn-affected berries may enhance fruit dehydration and increase the soluble solids concentration compared with healthy berries (Muganu et al. 2011).However, the concentration of soluble solids remained near 22 Brix in berries affected by sunburn, regardless of the visual severity of the damage.This may indicate that fruit dehydration is relevant to raise the soluble solids concentration in berries only at moderate severities of sunburn, as there was no increase in TSS for severely damaged berries.For healthy berries, the soluble solids concentration linearly increased from 15 to 21 Brix as hue values decreased from 100 to 70, reflecting the well-known connection between sugar accumulation and chlorophyll degradation in skins during the ripening of white grapevine cultivars.By contrast, berries affected by sunburn exhibited no change in soluble solids concentration (22 Brix), regardless of sunburn severity.The cessation of the TSS increase in berries occurred when the skin hue was near 65, as the inflection point of the quadratic regression between skin hue and TSS was equal to 0 at that value of hue.The linear regression analysis between hue and Fm indicated that hue values near 60 were associated with moderate visual symptoms of sunburn.This suggests that a hue of 60 in berry skins may be used as a color index to harvest the fruit in Muscat of Alexandria vines, as no gain in the soluble solids concentration and alcohol is expected at hue values below 60, which are associated with severe levels of sunburn.
The concentration of terpenes in grapes is generally high in areas that exhibit elevated air temperatures and solar radiation because these volatile compounds exhibit plant thermoprotective and antioxidant functions (Joubert et al. 2016).Our results showed that the concentration of several volatile compounds, as well as of total terpenes, tended to be higher in berries affected by sunburn, despite the lack of differences among sunburn severities.The exception was linalool, which had a concentration that was 1.5-fold higher in sunburn-affected berries compared with healthy berries.Linalool is one of the most relevant terpenes that characterize the aromatic profile in Muscat of Alexandria wines; therefore, our findings suggest that the occurrence of sunburn in berries is not necessarily negative for winemaking.The higher concentration of linalool in sunburn-affected berries may respond to a faster biosynthesis of this aromatic compound due to microclimate conditions that induce the appearance of sunburn, specifically sunlight intensity at the fruit zone after veraison, as reported by Belancic et al. (1997).In berries shaded during ripening, linalool has not been detected in the fruit at harvest, unlike other terpenes that have been distinguished in low concentrations (Friedel et al. 2016).In another study, the concentration of glycosylated linalool in sunlight-exposed berries gradually increased during ripening when previously shaded clusters were re-exposed to sunlight (Zhang et al. 2017).Conversely, higher concentrations of linalool have been found in severely defoliated Muscat of Alexandria vines (Pascual et al. 2017).In the biosynthesis process of linalool, there is a lightdependent decarboxylation phase that does not exist in the synthesis of other terpenes (Belancic et al. 1997), which may explain the lack of differences for the remaining volatile compounds analyzed in this study.Because no differences in linalool concentration were found among severities of sunburn, induction of severe sunburn does not appear to be necessary to improve the aromatic profile in Muscat grapes.The lowest concentration of volatile terpenes was detected in the first season, which coincided with the highest number of days above 35°C from veraison to harvest.Elevated air temperatures (>35°C) may increase the anaerobic respiration rate of berries, inducing the synthesis of reactive oxygen species and affecting the monoterpene synthesis pathway (Jiang et al. 2015).

Conclusions
Global warming is expected to increase maximum air temperatures and the frequency of heat waves across the world's wine regions.This may increase the incidence and severity of sunburn damage in grapes, especially in Ibarra I et al.
Sunburn Impact on Fruit Quality vineyards affected by a combination of temperature, radiation, and water stress.In the present study, visual symptoms of sunburn were apparent in as much as 40% of the analyzed fruit.This may be attributed to the overexposure of clusters from the bush-trained vines to environmental conditions, rather than to the existence of particularly extreme weather conditions.Despite the common belief that sunburn reduces wine quality, our results showed that moderate levels of sunburn may be positive for grapes used for the production of aromatic wines, in which the concentration of volatile terpenes plays a key role in defining wine quality.However, no gain in technical maturity or aromatic profile was observed when sunburn was severe or very severe, which highlights the importance of monitoring sunburn incidence and severity during ripening.

Figure 1
Figure 1 Bush training system in bush-trained Muscat of Alexandria vines under nonirrigated conditions in the Itata valley, Chile.Vines were trained at two heights from the soil (high, 50 cm; low, 2 to 10 cm) during the 2018 and 2019 seasons.

Figure 2
Figure 2 Scale used for the visual evaluation of skin appearance in berries from bush-trained Muscat of Alexandria vines under nonirrigated conditions in the Itata valley, Chile. 1 = Green berries (healthy); 2 = amber berries (slight); 3 = damage with skin browning (moderate); 4 = damage with dark browning (severe); 5 = damage with cell death (black skin) (very severe).

Figure 3
Figure 3 Weekly averages of solar radiation (A) and maximum air temperature (B) recorded at noon (1200 to 1500 hrs) from 1 Oct to 30 March in the 2018 and 2019 seasons at the Nueva Aldea agrometeorological station, Ñuble Region, Chile.

Figure 4
Figure 4 Percentage of berries from bush-trained Muscat of Alexandria vines under nonirrigated conditions in the Itata valley, Chile, showing different categories of sunburn damage (healthy, berries without lesions; moderate, faint reddish-brown lesions; severe, clear brown lesions; very severe, dark brown lesions) for the 2018 (A) and 2019 (B) seasons.

Figure 5
Figure 5 Quadratic relationship between nine hue categories and soluble solids concentration (Brix) at harvest time (end of March) of berries that were visually categorized by sunburn severity (healthy, berries without lesions; moderate, faint reddish-brown lesions; severe, clear brown lesions; very severe, dark brown lesions) in bush-trained Muscat of Alexandria vines under nonirrigated conditions in the Itata valley, Chile (-0.0028 x 2 + 0.36x + 10.5; R 2 = 0.59; p ≤ 0.05; n = 11).Error bars represent ±1 standard error of the mean.

Figure 6
Figure 6 Linear relationship between hue and maximum chlorophyll fluorescence (Fm) in skins of berries that were visually categorized by sunburn severity (healthy, berries without lesions; slight, faint reddishbrown lesions; moderate, faint reddish-brown lesions; severe, clear brown lesions; very severe, dark brown lesions) in bush-trained Muscat of Alexandria vines under nonirrigated conditions in the Itata valley, Chile at harvest time (5 April) (0.25 x + 0.72; R 2 = 0.72; p ≤ 0.0001; n = 15).

Figure 7
Figure 7 Orthogonal contrast analysis for linalool concentration in healthy (light-gray bar) and sunburned (dark-gray bar) berries of bushtrained Muscat of Alexandria vines under nonirrigated conditions in the Itata valley, Chile, in 2018 and 2019.Different letters indicate significant differences at a 95% confidence level (least significant difference).n = 6 to 12.

Table 2
Normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) of vineyards that exhibited two fruit zone heights (high, 50 cm; low, 2 to 10 cm) in bush-trained Muscat of Alexandria vines at veraison and harvest during the 2018 and 2019 seasons.
a Different letters indicate significant differences between columns at 95% confidence level (least significant difference).n = 3.

Table 3
Yield components and fruit quality parameters at two fruit zone heights (high, 50 cm; low, 2 to 10 cm) in bush-trained Muscat of Alexandria vines during the 2018 and 2019 seasons.
a Different letters indicate significant differences between columns at 95% confidence level (least significant difference).n = 3. 6 of 10