Shaded Fruit Research Articles

Canopy position affects rind biochemical profile of ‘Nules Clementine’ mandarin fruit during postharvest storage

This study was conducted to investigate the effects of preharvest canopy position and bagging treatments on rind physiological and biochemical properties of ‘Nules Clementine’ mandarin (Citrus reticulata Blanco) fruit. Before storage, the respiration rate of unbagged outside fruit was significantly higher (21.6mLCO2kg−1h−1) than of bagged inside fruit (16.3mLCO2kg−1h−1). Unbagged fruit outside the canopy had 1.4-fold higher carbohydrates, and 1.1-fold higher dry matter (DM) content than bagged inside fruit. Bagged fruit inside the canopy had higher (24%) weight loss than outside sun-exposed fruit (14%). This corresponded with a higher rind breakdown (RBD) index for bagged inside fruit, compared to sun-exposed fruit which did not develop the disorder. During postharvest storage, rind fructose levels of bagged fruit inside the canopy increased from 62.4mg/g DM at harvest to 81.3mg/g DM after 8 weeks, while those of unbagged outside fruit increased from 97.9 to 108.4mg/g DM. Concomitant with the increase in fructose, sucrose in rind tissue of bagged inside fruit decreased from 42.6 to 27.7mg/g DM and from 49.3 to 33.4mg/g DM for unbagged outside fruit. Rind glucose of unbagged inside fruit decreased from 90.6 to 76.2mg/g DM. Ascorbic acid concentrations remained almost constant during storage, with levels between 3.3 and 6.7mg/g DM for inside bagged and unbagged outside fruit, respectively. Hesperidin was the major flavanone detected, with concentrations between 35 and 45mg/g DM followed by narirutin (1.1–2.8mg/g DM). At harvest, rind of fruit harvested from outside the canopy had lower hesperidin concentration (38.1mg/g DM) compared to shaded fruit (44.2mg/g DM). Overall, the results suggest that variations in microclimatic conditions inside the tree canopy during the growing season affect the biochemical profile of the fruit rind, which in turn influences fruit response to postharvest stresses associated with senescence and susceptibility to RBD.

Shading affects flesh calcium uptake and concentration, bitter pit incidence and other fruit traits in “Greensleeves” apple

Bitter pit (BP) is a physiological disorder in apple (Malus×domestica Borkh) believed to be triggered by low Ca2+ concentrations in the fruit, and which may be influenced by environmental conditions. The objectives of this study were to explore the effects of tree shading on total and cell wall bound fruit Ca2+ content and fruit susceptibility to BP. ‘Greensleeves’ (GS) apple trees were cultivated under shaded and non-shaded conditions. The shading condition was applied 70 days after full bloom by reducing about 50% of the sunlight reaching the tree canopies. Shading increased stem water potential and leaf stomatal conductance. Bitter pit was observed only in shaded fruit. Cortical Ca2+ was most abundant in shaded fruit without BP symptoms, intermediary in shaded fruit with BP, and lowest in non-shaded fruit. The cell wall Ca2+ concentration was higher in shaded than non-shaded fruit, but shaded fruit with and without BP had similar cell wall Ca2+ concentrations. The degree of pectin deesterification and the expression of two pectin methylesterases (PME1 and PME2) were higher in shaded fruit than in non-shaded fruit. The percentage of total cortical Ca2+ bound to the cell wall was highest in shaded fruit with BP. Shaded fruit without BP had lower Mg2+ content and Mg2+/Ca2+ ratio in cortical tissue than shaded fruit with BP. The results indicate that although shade increases fruit Ca2+ uptake, it also enhances fruit susceptibility to BP by increasing Mg2+ uptake and Ca2+ binding to the cell wall in fruit cortical tissue.

EFFECT OF FRUIT POSITION IN THE CANOPY ON PHYSIOLOGICAL AGE AND PHYSICOCHEMICAL COMPOSITION OF MANGO 'COGSHALL'

By comparing 3 harvest stages for mango, corresponding to two stages (106 and 120 days after full bloom) and one stage at the onset of the climacteric rise (called 'yellow point' for Cv Cogshall), we demonstrated relationships between harvest stage and changes in some ripening and sensorial descriptors according to fruit position in the canopy (fruit and its fruit-bearing branch were either well-exposed to light or within the canopy, treatments named well-exposed and shaded fruit, respectively). Dry matter content and final sugar content (mainly sucrose) were lower in shaded fruit. Similar aromatic compounds were found in ripe fruit, but their contents depended on the fruit position in the canopy. Total aroma content decreased with the harvest stage, but this decrease was mainly due to the drop off of terpens content, the most abundant class. After ripening shaded fruit had a lower content in terpens (especially ?-3-carene) and a lower lactones content compared to well-exposed fruit. Most of these differences decreased with the harvest stage and were minimized at the latest harvest, corresponding to the yellow point stage. These results showed that the environmental conditions have an effect on the building and the growing of mango fruit in a same tree, and so on their physiological ages. An adapted pruning to facilitate access to light in the canopy is particularly important to obtain homogeneous batches. Moreover, the mixing of well-exposed and shaded fruits harvested at different green mature stages will induce heterogeneity and differences in quality of ripe fruit for the marketing network. (Resume d'auteur)

Response of the physiological parameters of mango fruit (transpiration, water relations and antioxidant system) to its light and temperature environment

Depending on the position of the fruit in the tree, mango fruit may be exposed to high temperature and intense light conditions that may lead to metabolic and physiological disorders and affect yield and quality. The present study aimed to determine how mango fruit adapted its functioning in terms of fruit water relations, epicarp characteristics and the antioxidant defence system in peel, to environmental conditions. The effect of contrasted temperature and light conditions was evaluated under natural solar radiation and temperature by comparing well-exposed and shaded fruit at three stages of fruit development. The sun-exposed and shaded peels of the two sides of the well-exposed fruit were also compared.Depending on fruit position within the canopy and on the side of a well-exposed fruit, the temperature gradient over a day affected fruit characteristics such as transpiration, as revealed by the water potential gradient as a function of the treatments, and led to a significant decrease in water conductance for well-exposed fruits compared to fruits within the canopy. Changes in cuticle thickness according to fruit position were consistent with those of fruit water conductance. Osmotic potential was also affected by climatic environment and harvest stage. Environmental conditions that induced water stress and greater light exposure, like on the sunny side of well-exposed fruit, increased the hydrogen peroxide, malondialdehyde and total and reduced ascorbate contents, as well as SOD, APX and MDHAR activities, regardless of the maturity stage. The lowest values were measured in the peel of the shaded fruit, that of the shaded side of well-exposed fruit being intermediate.Mango fruits exposed to water-stress-induced conditions during growth adapt their functioning by reducing their transpiration. Moreover, oxidative stress was limited as a consequence of the increase in antioxidant content and enzyme activities. This adaptive response of mango fruit to its climatic environment during growth could affect postharvest behaviour and quality.

Severe Shading Reduces Early Fruit Growth in Apple by Decreasing Cell Production and Expansion

Shading during early fruit development reduces fruit growth and initiates fruit abscission in apple (Malus ×domestica). The mechanisms mediating the decline in fruit growth in response to shading are not well understood. In this study, the effects of shading during early fruit development on cell production and expansion were investigated. Additionally, the effects of shading on the expression of genes associated with carbohydrate metabolism, fruit growth, and cell production and expansion were investigated to develop a better understanding of the molecular mechanisms and to identify genes that mediate the reduction in fruit growth. Shading of isolated branches or entire trees ≈15 to 18 days after full bloom resulted in a sharp decline in fruit growth by 3 days after treatment. Reduction in fruit growth was consistently mediated by a decline in cell production within 3 days after treatment. Reduced fruit growth was also associated with lower cell size by 3 to 7 days after shading in two different years. These data indicate that the reduction in fruit growth as a result of shading is mediated by a reduction in cell production and expansion. The expression of two sorbitol dehydrogenase (SDH) genes, MdSDH1 and MdSDH2, was higher in the shaded fruit by up to 10-fold, suggesting an increase in SDH activity to meet the immediate respiratory demands of the developing fruit. The auxin response factor (ARF), MdARF106, displayed ≈3-fold higher expression in the shaded fruit, suggesting its involvement in regulating mechanisms that mediate the reduction in fruit growth. Two A2-type cyclins, MdCYCA2;2 and MdCYCA2;3, which are positively associated with cell production, displayed lower expression in the shaded fruit by up to 4.6-fold. Conversely, MdKRP4 and MdKRP5, cell cycle genes negatively associated with cell production, displayed 3.9- and 5.3-fold higher expression in the shaded fruit, respectively. Additionally, two genes associated with cell expansion, MdCOB1 (cobra1) and MdEXPA10;1 (expansin), displayed lower expression in the shaded fruit. Together, these data indicate that shading results in coordinated changes in the expression of carbohydrate metabolism-related genes, key transcription factors related to fruit growth, and genes associated with cell production and expansion. These changes may subsequently decrease the progression of the primary processes that mediate fruit growth.

Compositional Changes in ‘Bartlett’ Pear (Pyrus communis L.) Cell Wall Polysaccharides As Affected by Sunlight Conditions

Preharvest conditions can have a great impact on fruit quality attributes and postharvest responses. Firmness is an important quality attribute in pear, and excessive softening increases susceptibility to bruising and decay, thus limiting fruit postharvest life. Textural characteristics of fruits are determined at least in part by cell wall structure and disassembly. Few studies have analyzed the influence of fruit preharvest environment in softening, cell wall composition, and degradation. In the current work 'Bartlett' pears grown either facing the sun (S) or in the shade (H) were harvested and stored for 13 days at 20 °C. An evaluation of fruit soluble solids, acidity, color, starch degradation, firmness, cell wall yield, pectin and matrix glycan solubilization, depolymerization, and monosaccharide composition was carried out. Sun-exposed pears showed more advanced color development and similar levels of starch degradation, sugars, and acids than shaded fruit. Sunlight-grown pears were at harvest firmer than shade-grown pears. Both fruit groups softened during storage at 20 °C, but even after ripening, sun-exposed pears remained firmer. Sunlight exposure did not have a great impact on pectin molecular weight. Instead, at harvest a higher proportion of water-solubilized uronic acids and alkali-solubilized neutral sugars and a larger mean molecular size of tightly bound glycans was found in sun-exposed pears. During ripening cell wall catabolism took place in both sun- and shade-grown pears, but pectin solubilization was clearly delayed in sun-exposed fruit. This was associated with decreased removal of RG I-arabinan side chains rather than with reduced depolymerization.

REFLECTIVE FABRIC IMPROVES INTRA-CANOPY LIGHT LEVELS AND INCREASES YIELD IN A LOW-DENSITY, MATURE 'D'ANJOU' PEAR ORCHARD

Reflective fabric was installed spring 2009 in a mature, low-density ‘d’Anjou’ pear orchard (269 trees ha-1) to investigate its influence on canopy light environment, fruit size, yield and postharvest fruit quality. Four treatments were studied: 1) no Fabric (NF), 2) fabric applied prior to full bloom (FB) and removed 75 days after full bloom (DAFB) (F-75), 3) full-season fabric applied prior to FB and removed at harvest (F-FS), and 4) shade, 60% shade-cloth applied 60 DAFB through harvest. Weekly fruit growth rate and average fruit size at harvest were not affected by fabric treatments. Shaded fruit were markedly smaller. Total tree yield was significantly greater for fabric treatments relative to the control (c.a., 20%), but not significantly different between fabric treatments, indicating that increased tree yields were due to an increase in fruit number, occurring between FB and 75 DAFB. Higher yields were observed for fabric treatments in the lower exterior, mid and interior canopy. Photosynthetic active radiation (PAR) was increased under fabric by 25, 90 and 30% in the exterior, mid and interior zones of the canopy, respectively. Measurement of reflected PAR from fabric was approximately15% of the total light incident on the canopy exterior, as opposed to approximately 2% over the grassed alleyways of NF. At harvest, firmness of exterior-canopy fruit was 64.7, 64.4 and 67.2 N for F-FS, shade and NF fruit, respectively, indicating advanced maturity of F-FS and shade fruit relative to NF. Fruit quality attributes (firmness, soluble solids (SS), total acids and extractable juice) were analyzed at 2, 4 and 5 months of regular atmosphere storage (-1°C), following a 7-day, 20°C ripening period. Slightly greater levels of SS were observed in FS fruit. Shade treatment fruit were significantly less firm and had lower sugar content.

The Effect of Natural Light on Changes in Antioxidant Content and Color Parameters of Vine-ripened Tomato (Solanum lycopersicum L.) Fruits

During the vine ripening of tomato fruits (Solanum lycopersicum L.), the change in antioxidant content and color was studied under two different solar exposures. An experiment was carried out in 2008 and 2009 to determine how color evolution, surface temperature, and antioxidant content of tomato fruits were influenced by fruit position and exposure on trellised tomato plants. Trellised rows were oriented so that non-shaded fruits were subjected to full solar irradiation from 0900 hr to 1600 hr, whereas shaded fruits were completely shaded during the same time period. A significant difference (P = 0.001) between fruit surface temperatures of shaded or non-shaded fruits was observed. The more direct solar irradiation the fruits were exposed to, the higher the fruit surface temperatures increased. At 1400 hr, only the average temperature of non-shaded fruits was significantly higher (7.0 and 9.3 °C in 2008 and 2009, respectively) than the air temperature. At the end of the ripening process, color change of non-shaded fruits showed significantly higher CIELab hue compared with shaded fruits. A close negative correlation (R2 = 0.51) was detected between the hue color parameters and the cumulative fruit surface–air temperature difference of non-shaded fruits, but in the case of shaded fruits, there was only a weak (R2 = 0.29) correlation. Solar exposure had a great effect on the antioxidant content of tomato fruits. A higher fruit surface temperature resulted in significantly less lycopene and more polyphenols and ascorbic acid content in tomato fruits.

Two-Season Study of the Influence of Regulated Deficit Irrigation and Reflective Mulch on Individual and Total Phenolic Compounds of Nectarines at Harvest and during Storage

The influence of deficit irrigation (Deficit) and reflective mulch (Reflective) of Caldesi 2000 nectarines on the content of individual phenolic compounds was studied at harvest and during storage for 2, 4, and 6 weeks at 2 °C during two consecutive years (2007 and 2008). Individual phenolic groups in the edible fruit part consisted mainly of proanthocyanidins (200 mg/100 g fw), lower content of phenolic acids (17 mg/100 g fw), and minor content of flavonols (5 mg/100 g fw) and anthocyanins (1.2 mg/100 g fw). Deficit irrigation increased the content of total phenolics, including proanthocyanidins and phenolic acids, reaching similar amounts in both years. Sun-exposed fruit (upper part of canopy) showed higher content than shaded fruit (lower part of canopy). However, Reflective significantly increased the content of total phenolics, particularly phenolic acids and proanthocyanidins, of fruit located in the lower part of the canopy. During storage, Deficit and Reflective did not affect the content of phenolic acids, flavonols, and proanthocyanidins when compared to the content at harvest. Optimizing cultural practices can be a way to increase the phenolic content of nectarines.

Relationships between internal ethylene and optical reflectance in ripening ‘Antonovka’ apples grown under sunlit and shaded conditions

The feasibility of non-destructive estimation of internal ethylene concentration (IEC) in apple fruit via fruit reflectance using recently developed approaches and a fiber-optics reflectometer was investigated. The relationships between IEC and fruit reflectance in the 400–800 nm range were studied in stored apple ( Malus × domestica Borkh., cv. Antonovka) fruit. A strong correlation between IEC and optical reflectance spectra taken from sunlit surfaces of the fruit was detected whereas reflectance of the shaded fruit surface showed a weak correlation with IEC. The increase of the reflectance in the red occurred along with IEC build-up during ripening resulting a strong ( r 2 > 0.80) correlation. By contrast, reflectance in the blue-green part of the spectrum remained low and was negatively ( r 2 ≈ 0.65) correlated with IEC. These observations are consistent with the phenomenon of degradation of chlorophylls which often occurs in parallel with the retention of carotenoids in ripening apple skin. As a result, IEC showed a significant correlation ( r 2 > 0.69; P < 0.001) with the index based on reflectances in the red and blue-green regions of the spectrum ( R 678 − R 480)/ R 800. The effects of strong solar light on the relationships between IEC and fruit reflectance are considered. The possibilities and limitations of a non-destructive reflectance-based assay of IEC in apple fruit are discussed.

Effects of Sunlight Exposure on Berry and Wine Monoterpenes and Sensory Characteristics of Traminette

Traminette is a cold-hardy interspecific Gewürztraminer hybrid winegrape cultivar grown in the eastern United States. A study from 2003 through 2005 investigated impacts of canopy management on aromatic qualities of fruit and wine. Cluster-shading treatments under leaf layers (0, 1, 2, and &gt;3) and synthetic coverings (greenhouse shade cloth and light-excluding apple bags) were implemented in field trials, and fruit composition and wine sensory analyses were conducted. Fruit from fully exposed clusters had 30% higher concentrations of potentially volatile terpenes compared with heavily shaded fruit (&gt;3 leaf layers). Descriptive analyses showed higher ratings for color, linalool, rose, and spice aromas with exposed wines in 2004. There were no differences in wine aroma intensities in 2005. Berry skin color at harvest correlated with potentially volatile terpenes concentration and may be used as a field guide to estimate monoterpene concentration at harvest.

Post-veraison sunlight exposure induces MYB-mediated transcriptional regulation of anthocyanin and flavonol synthesis in berry skins of Vitis vinifera

Anthocyanins, flavan-3-ols, and flavonols are the three major classes of flavonoid compounds found in grape berry tissues. Several viticultural practices increase flavonoid content in the fruit, but the underlying genetic mechanisms responsible for these changes have not been completely deciphered. The impact of post-veraison sunlight exposure on anthocyanin and flavonol accumulation in grape berry skin and its relation to the expression of different transcriptional regulators known to be involved in flavonoid synthesis was studied. Treatments consisting of removing or moving aside the basal leaves which shade berry clusters were applied. Shading did not affect sugar accumulation or gene expression of HEXOSE TRANSPORTER 1, although in the leaf removal treatment, these events were retarded during the first weeks of ripening. Flavonols were the most drastically reduced flavonoids following shading and leaf removal treatments, related to the reduced expression of FLAVONOL SYNTHASE 4 and its putative transcriptional regulator MYB12. Anthocyanin accumulation and the expression of CHS2, LDOX, OMT, UFGT, MYBA1, and MYB5a genes were also affected. Other regulatory genes were less affected or not affected at all by these treatments. Non-transcriptional control mechanisms for flavonoid synthesis are also suggested, especially during the initial stages of ripening. Although berries from the leaf removal treatment received more light than shaded fruits, malvidin-3-glucoside and total flavonol content was reduced compared with the treatment without leaf removal. This work reveals that flavonol-related gene expression responds rapidly to field changes in light levels, as shown by the treatment in which shaded fruits were exposed to light in the late stages of ripening. Taken together, this study establishes MYB-specific responsiveness for the effect of sun exposure and sugar transport on flavonoid synthesis.

Berry Temperature and Solar Radiation Alter Acylation, Proportion, and Concentration of Anthocyanin in Merlot Grapes

Using a forced convection system, temperatures of Merlot grape clusters were monitored and controlled between veraison and harvest to produce a dynamic range of berry temperatures under field conditions in both sun-exposed and shaded fruit. Ten combinations of temperature and solar radiation exposure were used to quantify effects on phenolic profiles (anthocyanins and flavonol-glycosides) and on total concentrations of skin anthocyanin (TSA) in the fruit at commercial maturity. Exposure of berries to high temperature extremes for relatively short periods during ripening appears to alter the partitioning of anthocyanins between acylated and nonacylated forms and between dihydroxylated and trihydroxylated branches of the anthocyanin biosynthetic pathway. Specifically, among flavonol-glycosides, quercetin 3-glucoside increased with exposure to solar radiation. Low incident solar radiation alone appeared not to compromise total anthocyanin accumulation; rather, a combination of low light and high berry temperatures decreased TSA. Regardless of exposure to solar radiation, higher berry temperatures led to a higher concentration and a higher proportion of TSA comprised by malvidin-based anthocyanins, driven primarily by increases in the acylated derivatives. Under shade alone and under high temperature extremes in sunlit and shaded fruit, acylated anthocyanins represented a larger proportion of TSA than did nonacylated anthocyanins. At berry temperatures equivalent to those of shaded fruit, exposure to solar radiation decreased the proportion of TSA comprised by acylated forms of the five base anthocyanins and increased the proportion of TSA comprised by dihydroxylated anthocyanins. Results indicate a complex combined effect of solar radiation and berry temperature on anthocyanin composition, synergistic at moderate berry temperatures and potentially antagonistic at high temperature extremes.

The effect of bunch shading on berry development and flavonoid accumulation in Shiraz grapes

Opaque boxes were applied to bunches of Shiraz grapesprior to flowering to determine the effect of sunlight on berry developmentand accumulation of flavonoids. The boxes were designed to maintain airflowwhile excluding light and thus to minimise changes in temperature andhumidity. There was no significant effect of shading on sugar accumulationand in two of the three seasons studied there was no effect on berryweight. Chlorophyll concentration was much lower in the shaded fruit, whichappeared pale yellow until veraison. The fruit coloured normally in theshaded bunches and in two of the three seasons there was no significantchange in anthocyanin content. Expression of the gene encoding UDP-glucoseflavonoid-3-O-glucosyl transferase (UFGT), a key gene in anthocyaninsynthesis, increased after veraison and was similar in both shaded andexposed fruit. Anthocyanin composition was altered in the shaded fruit,which had a greater proportion of the dioxygenated anthocyanins, theglucosides of cyanidin and peonidin. Shading had no significant effect onthe levels of condensed tannins in the skin or seeds of ripe fruit. Shadingsignificantly reduced the levels of flavonols in the grape skin. In theexposed fruit, flavonol concentration was highest around flowering thendeclined as the berries grew, but there was an increase in flavonols perberry during ripening. When the boxes were applied before flowering, shadedfruit had much lower levels of flavonols throughout berry development andat harvest the level of flavonols were less than 10% of that in exposedfruit. A gene encoding flavonol synthase (FLS) was expressed at floweringand during ripening in exposed grapes but its expression was greatlyreduced in shaded fruit. The results indicate that shading had littleeffect on berry development and ripening, including accumulation ofanthocyanins and tannins, but significantly decreased flavonol synthesis.

Partial Shading of Cabernet Sauvignon and Shiraz Vines Altered Wine Color and Mouthfeel Attributes, but Increased Exposure Had Little Impact

Few studies have investigated the impact of vine shading on the sensory attributes of the resultant wine. This study examines the effects of canopy exposure levels on phenolic composition plus aroma, flavor, and mouthfeel aspects in wine. Wines were made from Cabernet Sauvignon and Shiraz grapes (Vitis vinifera L.) subjected to different levels of canopy exposure in a commercial vineyard in the Sunraysia region, Victoria, Australia. Canopy exposure treatments included control (standard vineyard practice), exposed (achieved with a foliage wire 600 mm above the top cordon), highly exposed (using a foliage wire with leaf plucking in the fruit zone), and shaded treatment (using 70% shade-cloth). Spectral and descriptive analyses showed that levels of anthocyanins, other phenolics, and perceived astringency were lower in wines made from shaded fruit; however, the reverse was generally not observed in wines of exposed and highly exposed fruit. Descriptive analysis also showed wines from the shaded fruit were different from other treatments for a number of flavor and aroma characters. These findings have implications for vineyard management practices.

Exclusion of sunlight from Shiraz grapes alters wine colour, tannin and sensory properties

The aim of this study was to determine how changes in grape composition brought about by artificial shading (sunlight exclusion) influence wine properties including colour, flavonoid composition and sensory attributes. Prior to flowering, bunches of Shiraz grapes were enclosed in boxes designed to eliminate light without altering bunch temperature and humidity. This artificial bunch shading had little effect on berry ripening and accumulation of sugar but at harvest the shaded bunches had smaller berries and higher seed weight, juice pH and titratable acidity. The amount of anthocyanins in the fruit was not changed significantly but anthocyanin composition in the shaded berries was shifted towards dioxygenated anthocyanins (the glucosides of cyanidin and peonidin derivatives). Shaded fruit had increased seed tannins and decreased skin tannins but the largest relative change in flavonoids was a marked decrease in flavonols in the shaded fruit, similar to previous studies. Wines made from shaded fruit had lower wine colour density, total phenolics, anthocyanins and tannins when the wine was bottled and after ageing for up to three years. Analysis of potential flavour compounds following acid hydrolysis indicated that the wines made from shaded fruit had decreased levels of glycosides of β-damascenone and 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN). Sensory analysis of the wines indicated no significant difference in aroma attributes but the wines made from shaded fruit were rated lower for astringency, fruit flavour and flavour persistence in-mouth sensory attributes. The results indicate that extreme shading of Shiraz fruit can decrease wine colour, anthocyanins and tannins as well as altering sensory attributes.

Effect of Shading on Accumulation of Flavonoid Compounds in (Vitis vinifera L.) Pinot Noir Fruit and Extraction in a Model System

Accumulation and compositional changes of flavonols, proanthocyanidins, and anthocyanins were measured in Vitis vinifera L. cv. Pinot noir in shaded and exposed treatments. In addition, extraction of these compounds into a model wine solution was measured. The study was conducted in a commercial vineyard within a uniform zone of relatively low vigor vines. Light exclusion boxes were installed on pairs of clusters on the same shoot (shaded treatment), and a second set of clusters on an adjacent shoot were labeled as the exposed treatment. Fruit samples were harvested at the onset of ripening (véraison) and at commercial harvest. Cluster shading resulted in a substantial decrease in mg/berry accumulation of flavonols and skin proanthocyanidins and minimal differences in anthocyanins. In analyzing seed proanthocyanidins by phloroglucinolysis, shaded and exposed treatments were similar at véraison; however, by harvest, the shaded treatment had higher extension and terminal subunits (nmol/seed) as compared to the exposed treatment. For skin proanthocyanidins, shaded fruit was lower for all subunits (nmol/berry) at both véraison and harvest. Shading caused an increase in the proportion of (-)-epicatechin and a decrease in (-)-epigallocatechin at harvest in skin extension subunits. Seed proanthocyanidins in shaded fruit contained a lower proportion of (+)-catechin and a higher proportion of (-)-epicatechin-3-O-gallate in extension subunits and a lower proportion of (+)-catechin and (-)-epicatechin-3-O-gallate and a higher proportion of (-)-epicatechin in terminal subunits. For anthocyanins, the shaded treatment had a proportional reduction in delphinidin, cyanidin, petunidin, and malvidin and a large increase in peonidin glucosides. The model extractions from the two treatments paralleled differences in the fruit with a lower concentration of flavonols, anthocyanins, and proanthocyanidins in the shaded treatment. The skin proanthocyanidin percent extraction was found to be approximately 17% higher in the exposed model extraction than the shaded treatment.

SEPARATING HIGH HARVEST TEMPERATURE EFFECTS ON POSTHARVEST AVOCADO QUALITY

The logistics of the current Australian and Californian recommendations to harvest avocado below 30 °C and remove field heat within 6 hours of harvest are increasingly being challenged as the Western Australian industry expands. Despite this, there has been little feedback of quality sacrifice in the market as a result. Through factorial experiments, we harvested both shaded and sun-exposed 'Hass' avocado over an ambient air temperature range of 27-34 °C, subjected to a 2, 6 or 24 h pre-cooling delay and a 14 or 28 day cool-storage, before ripening and quality assessment. We found significant temperature correlations to softening, vascular browning, body rots and, when a temperature-by-delay interaction was considered, skin colour. The relationships of temperature to softening and body rot were quadratic: softening increased significantly up to an ambient temperature of about 30 °C but did not change significantly thereafter; body rots did not change significantly up to 30 °C but declined significantly thereafter. The interaction effect of temperature-by-delay on colour was also quadratic when fruit were subjected to a 24 h pre-cooling delay. Fruit colour increased significantly up to about 30 °C but did not change significantly thereafter. The relationship of temperature to vascular browning was negatively linear; showing a significant decline over the range of 27-34 °C. There was no significant main effect of sun-exposure, although there were significant interactions; showing that postharvest behaviour varied between shaded and sun-exposed fruit. However, the average elevation of 6 °C above shaded fruit temperatures was not as large as reported by previous studies and was thus interpreted with caution. In light of the results, experiments have been designed to further explore the main effects and interactions of temperature, sunlight, and postharvest handling on avocado quality and physiology.

Postharvest quality of ‘Laetitia’ and ‘Songold’ ( Prunus salicina Lindell) plums as affected by preharvest shading treatments

Non-uniform fruit quality within export consignments of plums compromises retailer and consumer satisfaction and thus, profitable marketing. Variability of maturity and quality at harvest and following storage and ripening period is thought to be strongly influenced by canopy light conditions during fruit development, in conjunction with once-off harvesting practices. During 2000/01 and 2001/02, the plum cultivars Prunus salicina Lindell ‘Laetitia’ and ‘Songold’ were subjected to different levels of shading by bagging entire scaffold branches with shade netting. Resulting light treatments gave 100 (control, no bags), 70, 45 and 25% photosynthetic photon flux density (PPFD). Fruit quality was assessed at harvest (once-off) following simulated commercial dual temperature storage (10 days at −0.5 °C followed by 8 days at 7.5 °C) and following 5–7 days of ripening at 15 °C. Shaded (≤70% PPFD) ‘Laetitia’ plums were less mature at harvest than exposed fruit and were smaller and firmer with a greener ground colour, lower soluble solids concentration (SSC) and poorer red colour. During postharvest cold storage, ripening processes proceeded more rapidly in shaded fruit relative to non-shaded fruit. This resulted in shelf quality not much inferior to fruit grown under high light conditions, since differences in firmness and SSC were reduced. However, under preharvest light levels less than 70% skin ground and red colour of ripe fruit remained poorer. Shaded ‘Songold’ plums were slightly greener and had lower SSC at harvest, but treatment differences became non-significant after storage and ripening. Postharvest internal disorders were virtually absent in both cultivars during both seasons. Based on our findings, we propose that plum tree canopies should be managed in such a way as to ensure light exposure of at least 70% in all bearing positions, which should result in more uniform maturity and postharvest quality of plums. Strip-picking is discouraged, since this will result in mixed quality on the shelf, particularly with regard to colour.

Effects of Sunlight Exposure on Cluster Monoterpene Levels of `Traminette' Grapes

Monoterpenes are organic compounds found in high quantities in certain wine grape varieties, such as Riesling, Gewürztraminer, and muscat-flavored varieties. These compounds exist in free and glycosidic form, and produce the characteristic aromas of such varieties. Traminette, released in 1996 as NY65.0533.13, is a cross between Joannes Seyve 23.416 and Gewürztraminer. This variety may be an alternative to Gewürztraminer in areas where cold temperatures prevent cultivation of such cold-tender varieties. The objective of this study is to determine the extent of which sunlight exposure influences monoterpene production in `Traminette'. Various exposure levels were obtained through synthetic coverings and ambient shading. Fully exposed clusters on a vertically shoot positioned canopy received 55% of ambient light whereas clusters with 50 and 70% shade cloth received 14.7 and 5.3%, respectively. Heavily shaded clusters (3+ leaf layers) received 2% of ambient light, and fully covered clusters received no light from véraison to harvest. Despite large differences in exposure level, cluster temperatures did not differ significantly between treatments. Results of monoterpene quantification show potentially volatile terpene (PVT) levels were 10-fold greater than free volatile terpene (FVT) levels in all treatments. PVT levels differ significantly between exposure groups in all locations at harvest, with exposed fruit having the highest concentration (6.5-7.5 mg L-1). Heavy and moderate shade fruit had 25% lower PVT levels compared to exposed fruit. Fully covered clusters had 34% less PVT, whereas 50 and 70 shade cloth clusters were 20% lower than exposed. Subsequent years of research will further validate preliminary findings of this study.