Shaded Fruit Research Articles

Sun exposure and high preharvest fruit temperatures increase antioxidants, heat shock proteins and thermotolerance of mango fruit (Mangifera indica L.)

ABSTRACT Preharvest sun-exposure can improve the tolerance of fruit during postharvest handling conditions and thus we examined the postharvest responses of mangos. Sun-exposed and shaded fruit of ‘Keitt’ and ‘Reynal’ mango were harvested and assessed for external and internal damage following postharvest hot water (HW 55°C/50min) and hot air (HA 47°C/20min; 49°C/90min) treatments used for fruit fly disinfestation. Heat shock proteins and antioxidant systems were examined as possible biochemical strategies for stress protection of fruit tissues. With maximum air temperatures <37°C, fruit exposed to direct sunlight reached temperatures up to 47°C. Following HW, sun-exposed ‘Reynal’ fruit had less external damage than shaded fruit, with damage mainly on the exposed surfaces. In contrast, sun-exposed and shaded ‘Keitt’ fruit had similar levels of damage following HW. For both cultivars, HA treatments of either sun-exposed or shaded fruit did not cause any significant external damage, but internal damage was observed. Both cultivars exhibited biochemical stress responses. Hsp17.4 in the flesh of sun-exposed ‘Reynal’ and ‘Keitt’ fruit were 2 and 6 times higher than in shaded fruit, respectively. Total polyphenols and anthocyanins were higher in tissues of sun-exposed than shaded fruit. Results are discussed in terms of the different biochemical defence strategies among these cultivars.

Effect of Water Stress and Shading on Lime Yield and Quality.

The aim of this study was to test the combined effect of water stress and cropping system on yield and fruit quality in Bearss lime trees. For this purpose, two irrigation treatments were applied during stage II of fruit growth: control (well irrigated, automatically managed by soil water content sensors) and stress (non-irrigated), both under open-field and shaded conditions. Soil water status was assessed by determining soil water content and plant water status by measuring stem water potential (Ψstem), stomatal conductance (gs), and net photosynthesis (Pn). Yield parameters (kg and the number of fruits per tree and fresh mass per fruit) and fruit quality were assessed on two harvest dates. In addition, on the second harvest date, the content of metabolites and nutrients in the lime juice was analyzed. The results showed that soil water deficit induced 35% lower gs values in open-field than in shaded conditions. The highest kg and the number of fruits per tree were observed in the shaded system, especially on the first harvest date. The lowest yield was observed in stressed trees grown without netting. Slightly higher fresh mass and equatorial diameter were observed in shaded fruits than in open-field fruit. Soil water deficit increased fruit total soluble solids and decreased juice content, especially in open-field trees. Shaded conditions made the lime trees more resilient to soil water deficit, which led to higher yields and better external fruit quality traits. In addition, fruit precocity was significantly higher in the shaded system.

Effects of calcium on cell wall metabolism enzymes and expression of related genes associated with peel creasing in Citrus fruits.

Fruit peel creasing is a serious pre-harvest physiological disorder in citrus, influencing fruit quality, storage, and yield. Four- and eight-year-old 'Hongjiang' oranges grafted onto Canton lemon rootstocks were treated with calcium and calcium inhibitors, respectively, to study the effects of different treatments on fruit creasing rate, mechanical properties of the peel, cell wall metabolism enzyme activities, and the expression of related genes. Foliar application of 0.5% calcium nitrate significantly reduced the fruit creasing rate, while treatment with EGTA and LaCl3, inhibitors of calcium uptake, increased the fruit creasing rate; But the effect of calcium nitrate treatment on changing the mechanical properties of pericarp and inhibiting the activity of hydrolase (PG, Cx and PE) was not very significant. Furthermore, it was observed that the expression levels of genes (PG, Cx, and PE) encoding cell wall-degrading enzymes were significantly lower in the normal fruit peel than in the creased fruit peel. Meanwhile, the expression levels of PG, Cx, and PE were higher in the peel of shaded fruit than in the peel of exposed fruit. During the high incidence period of fruit creasing, calcium nitrate treatment down-regulated the expression of PG, Cx, and PE, while EGTA treatment up-regulated the expression of these genes. In conclusion, foliar spraying of calcium nitrate at the fruit rapid enlargement stage can increase the Ca content in the peel of 'Hongjiang' orange and significantly suppress the expression of cell wall degrading enzymes genes (PG, PE and Cx) in 'Hongjiang' orange peel during the high occurrence period of fruit creasing, resulting in reducing the occurrence of fruit creasing and cracking.

Shading apple trees with an agrivoltaic system: Impact on water relations, leaf morphophysiological characteristics and yield determinants

• Study of the effects of fluctuating shading on an apple orchard using agrivoltaism. • Shading in orchard allowed a less stressful environment and reduced water needs. • Shading increased specific leaf area and reduced leaf photosynthetic rates. • Strong shading over 3 years reduced floribundity and alternate bearing behaviour. • Shading has low impact on fruit size due to higher water content in shaded fruits. The installation of dynamic photovoltaic panels over apple orchards could meet the challenges of protecting orchards from climate change and drive the energetic transition. However, the impact of solar panel's shading on apple performance needs to be investigated before being commercially adopted. A dynamic agrivoltaic system was installed in the south of France over a 10-year-old 'Golden Delicious' apple orchard and studied during three experimental seasons (2019–2021). This study aimed to evaluate the impact of fluctuating shading (photovoltaic panel orientation to maximise panel light interception) on water relations, leaf morphophysiological characteristics and yield determinants. With the selected photovoltaic design and strategy, trees were grown under a fluctuating shading (variable shading between 4% and 88% during the day) with a mean shading rate of 50–55%. On average, the air temperature was reduced by 3.8 °C, while relative humidity was increased by 14% under shading conditions. Depending on the season, the lower radiation and stressful microclimate decreased the irrigation between 6% and 31%. Fluctuating shading reduced the photosynthetic capacity of leaves and increased their specific leaf area (thinner leaves). The reduction in carbohydrate assimilation under shading was associated with lower starch reserve accumulation in the shoots (-7%), lower flower intensity at the shoot scale (-31%) and a lower proportion of trees with a high floribundity in 2020 (-45%). However, less alternate bearing was observed under shading, and better frost protection resulted in a higher proportion of trees bearing fruit under photovoltaic panels (+31%) and number of fruits per fruit-bearing tree (+44%) in 2021. Fruit size was less sensitive than fruit number to shading. Fruit size was reduced by 17% in 2019 but maintained in 2020 and 2021, probably due to a better water status of shaded trees that accumulated more water. Fruit dry matter content under shading was reduced by an average of 24%. In conclusion, agrivoltaic systems may reduce alternate bearing behaviour in apple trees, showing the importance of carrying out a multi-year study. However, the fluctuating shading strategy tested in this study did not maintain sufficient yields, with yields below 40 t/ha in all three years of study. Identifying the positive and negative effects of shading in this study may be useful for the development of sustainable apple orchard shading strategies.

Effects of Fruit Shading on Gene and Protein Expression During Starch and Oil Accumulation in Developing Styrax tonkinensis Kernels

Styrax tonkinensis has great potential as a biofuel feedstock source having industrial oilseeds with excellent fatty acids (FAs) composition and good fuel properties. Photosynthesis in the developing pericarp could affect the carbon distribution in kernel. During kernel development, more carbon sources are allocated to starch rather than lipid, when the pericarp photosynthesis is reduced by fruit shading treatment. After shading the fruits at 50 days after flowering (DAF), samples of shaded fruit (FSK) and controls (CK) were collected at 80 DAF and analyzed using the proteomic method. We identified 3,181 proteins, of which 277 were differentially expressed proteins, all downregulated in the FSK group. There were 56 proteins found involved in carbohydrate metabolism and lipid biosynthesis leading to oil accumulation with their iTRAQ ratios of FSK/CK ranging from 0.7123 to 1.1075. According to the qRT-PCR analyses, the key genes related to FA and triacylglycerol (TAG) biosynthesis were significantly downregulated between 60 and 90 DAF especially at 80 DAF, while the key genes involved in starch biosynthesis and FA desaturase had no significant difference between the two groups at 80 DAF. Fruit shading is a negative treatment for lipid accumulation but not starch accumulation by restraining enzymic protein expression involved in FA and TAG biosynthesis during S. tonkinensis kernel development.

Online recognition and yield estimation of tomato in plant factory based on YOLOv3

In order to realize the intelligent online yield estimation of tomato in the plant factory with artificial lighting (PFAL), a recognition method of tomato red fruit and green fruit based on improved yolov3 deep learning model was proposed to count and estimate tomato fruit yield under natural growth state. According to the planting environment and facility conditions of tomato plants, a computer vision system for fruit counting and yield estimation was designed and the new position loss function was based on the generalized intersection over union (GIoU), which improved the traditional YOLO algorithm loss function. Meanwhile, the scale invariant feature could promote the description precision of the different shapes of fruits. Based on the construction and labeling of the sample image data, the K-means clustering algorithm was used to obtain nine prior boxes of different specifications which were assigned according to the hierarchical level of the feature map. The experimental results of model training and evaluation showed that the mean average precision (mAP) of the improved detection model reached 99.3%, which was 2.7% higher than that of the traditional YOLOv3 model, and the processing time for a single image declined to 15 ms. Moreover, the improved YOLOv3 model had better identification effects for dense and shaded fruits. The research results can provide yield estimation methods and technical support for the research and development of intelligent control system for planting fruits and vegetables in plant factories, greenhouses and fields.

Under-Vine Vegetation Mitigates the Impacts of Excessive Precipitation in Vineyards.

Excessive precipitation events have greatly increased in several grape growing regions due to human-caused climate change. These heavy downpours result in a myriad of problems in the vineyard including soil aggregate breakdown, soil runoff, nutrient leaching, excessive vine vegetative growth, and diseased fruit. The negative impacts of excessive precipitation events on vineyards are exacerbated by the maintenance of bare soil under the vines. Exposure of bare soil results in soil erosion and runoff which pollutes nearby watersheds; raindrops weaken and break apart soil aggregates, leading to increased soil erosivity and contributing to the formation of surface crusts. In addition to excessive precipitation events, some grape growing regions can be characterized by fertile soils. The availability of ample water and nutrients can lead to highly vigorous vines with shoot growth continuing through harvest. Long shoots and large leaves result in shaded fruit, a humid vine microclimate, and excessive cluster rot. In this review, we examined how either natural (i.e., resident) or seeded under-vine vegetation (UVV) can help mitigate many of the problems associated with excessive precipitation. Through providing vegetative coverage to reduce the force of raindrops, increasing soil organic matter and enhancing soil microbial diversity, UVV can reduce the soil degradation and off-site impacts caused by excessive precipitation events. Through competition for soil resources, UVV can reduce excessive vegetative growth of vines and decrease cluster rot incidence and severity, although grapevine response to UVV can be highly variable. We discussed recent advances in understanding below and aboveground vine response and acclimation to UVV and presented current evidence of factors influencing the impact of UVV on vine growth and productivity to assist practitioners in making informed decisions and maximize the ecosystem services provided by UVV.

On Combining DeepSnake and Global Saliency for Detection of Orchard Apples

For the fast detection and recognition of apple fruit targets, based on the real-time DeepSnake deep learning instance segmentation model, this paper provided an algorithm basis for the practical application and promotion of apple picking robots. Since the initial detection results have an important impact on the subsequent edge prediction, this paper proposed an automatic detection method for apple fruit targets in natural environments based on saliency detection and traditional color difference methods. Combined with the original image, the histogram backprojection algorithm was used to further optimize the salient image results. A dynamic adaptive overlapping target separation algorithm was proposed to locate the single target fruit and further to determine the initial contour for DeepSnake, in view of the possible overlapping fruit regions in the saliency map. Finally, the target fruit was labeled based on the segmentation results of the examples. In the experiment, 300 training datasets were used to train the DeepSnake model, and the self-built dataset containing 1036 pictures of apples in various situations under natural environment was tested. The detection accuracy of target fruits under non-overlapping shaded fruits, overlapping fruits, shaded branches and leaves, and poor illumination conditions were 99.12%, 94.78%, 90.71%, and 94.46% respectively. The comprehensive detection accuracy was 95.66%, and the average processing time was 0.42 s in 1036 test images, which showed that the proposed algorithm can effectively separate the overlapping fruits through a not-very-large training samples and realize the rapid and accurate detection of apple targets.

Shading affects fracture force and fracture strain of apple fruit skins

Simple observation shows that naturally shaded apple fruit are more prone to russeting than sun-exposed fruit. The formation of microcracks in the fruit skin is the first visible sign of russeting. Our objective was to establish the effects of different levels of shading on the mechanical properties of apple (Malus × domestica Borkh.) fruit skins.Exposure of developing ‘Idared’ apples to visible and UV light was varied by shade-bagging and by sampling fruit from naturally shaded and exposed positions in the canopy. Fruit exposure to UV light was also varied using UV-absorbing film. Epidermal skin segments were excised, the cuticular membranes were isolated enzymatically and both were subjected to uniaxial tensile testing.Partial shading or blocking of UV light decreased the frequency of fruit having a red surface and also reduced the intensity of the red coloration, as indexed by increases in hue angle. The stiffness of epidermal skin segments was not affected by partial shading but fracture force and fracture strain were decreased. Blockage of UV slightly increased stiffness and decreased fracture force and fracture strain. The stiffness, fracture force and fracture strain of isolated cuticle samples were all markedly less than of epidermal skin segments. This indicates that, regardless of light treatment (visible and/or UV), it is the cellular layers of the skin, not the cuticle, that represent the load-bearing structure.There were no effects of shading or of UV blockage on cell size, cell shape or cell aspect ratio of either epidermal or hypodermal cells, or on sizes of parenchyma cells.There were also no detectable effects of shading or of UV blockage on thickness or wax content of the cuticle.We conclude that the effect of shading (visible and UV light) on the mechanical properties of the apple fruit skin was small, but was nevertheless consistent with an increase in the russet susceptibility of shaded fruit.

Effect of environmental factors on skin pigmentation and taste in three apple cultivars

To assess the effects of both development and environment on apple fruit quality, skin color and flavor/taste characteristics were compared between shaded (bagged) and sun-exposed (without bagging) apple fruit. Field experiments were conducted during the middle-to-late fruit development, using three cultivars (non-red ‘Golden Delicious’, pale-red ‘Cripps Pink’, and deep-red ‘Qinguan’) at 830.9 m altitude, and two cultivars (‘Qinguan’ and ‘Golden Delicious’) at three different altitudes (519.8, 830.9, and 1072.5 m). The chromaticity values L*, C*, and h° differed between non-red and both red cultivars over time. Sun-exposed fruits contained more chlorophyll and carotenoids than shaded fruits. Trace amounts of anthocyanin accumulated in the skin of sun-exposed ‘Golden Delicious’, while shading prevented anthocyanin accumulation in red cultivars. The sugar contents of all three tested cultivars increased over time, while the organic acid contents decreased. Shading reduced the sugar and organic acid contents but did not affect their variation trends over time. The growing environments affected both the h° values and pigment contents of ‘Qinguan’, and the maximum fructose and sucrose proportions and the minimum glucose proportion were detected at the lowest altitude. Although red peel color, sugars, and organic acid proportion were determined via genetic cues under natural conditions, the growing environment is centrally important for these traits. Both the temperature and light of the planting region influenced each other and impacted the contents of sugars and organic acids in the tested apple fruit.

Genome-wide survey of cytochrome P450 genes in the salmon louse Lepeophtheirus salmonis (Kr\xf8yer, 1837)

BackgroundThe salmon louse (Lepeophtheirus salmonis) infests farmed and wild salmonid fishes, causing considerable economic damage to the salmon farming industry. Infestations of farmed salmon are controlled using a combination of non-medicinal approaches and veterinary drug treatments. While L. salmonis has developed resistance to most available salmon delousing agents, relatively little is known about the molecular mechanisms involved. Members of the cytochrome P450 (CYP) superfamily are typically monooxygenases, some of which are involved in the biosynthesis and metabolism of endogenous compounds, while others have central roles in the detoxification of xenobiotics. In terrestrial arthropods, insecticide resistance can be based on the enhanced expression of CYPs. The reported research aimed to characterise the CYP superfamily in L. salmonis and assess its potential roles in drug resistance.MethodsLepeophtheirus salmonis CYPs were identified by homology searches of the genome and transcriptome of the parasite. CYP transcript abundance in drug susceptible and multi-resistant L. salmonis was assessed by quantitative reverse transcription PCR, taking into account both constitutive expression and expression in parasites exposed to sublethal levels of salmon delousing agents, ecdysteroids and environmental chemicals.ResultsThe above strategy led to the identification of 25 CYP genes/pseudogenes in L. salmonis, making its CYP superfamily the most compact characterised for any arthropod to date. Lepeophtheirus salmonis possesses homologues of a number of arthropod CYP genes with roles in ecdysteroid metabolism, such as the fruit fly genes disembodied, shadow, shade, spook and Cyp18a1. CYP transcript expression did not differ between one drug susceptible and one multi-resistant strain of L. salmonis. Exposure of L. salmonis to emamectin benzoate or deltamethrin caused the transcriptional upregulation of certain CYPs. In contrast, neither ecdysteroid nor benzo[a]pyrene exposure affected CYP transcription significantly.ConclusionsThe parasite L. salmonis is demonstrated to possess the most compact CYP superfamily characterised for any arthropod to date. The complement of CYP genes in L. salmonis includes conserved CYP genes involved in ecdysteroid biosynthesis and metabolism, as well as drug-inducible CYP genes. The present study does not provide evidence for a role of CYP genes in the decreased susceptibility of the multiresistant parasite strain studied.

Light Regulation of Carotenoid Biosynthesis in the Peel of Mandarin and Sweet Orange Fruits.

Carotenoids are the pigments responsible for the coloration of the peel and pulp of Citrus fruits. Light is one of the major environmental factors influencing coloration and carotenoid content and composition of fleshy fruits and therefore their commercial and nutritional quality. Agronomical observations indicate that citrus fruits exposed to sunlight develop a brighter peel coloration than shaded fruit inside the tree canopy. In the present study, the effect of light deprivation on carotenoid profile, and in the expression of genes of carotenoid metabolism and their precursors have been analyzed in fruits of Clemenules mandarin (Citrus clementine) and Navelina orange (Citrus sinensis). Fruit shading accelerated peel degreening, chlorophyll degradation, and reduced chloroplastic-type carotenoids. Time-course shading experiments revealed that the stage of fruit ripening appears to be determinant for the effect of darkness in carotenoid biosynthesis. Fruit shading produced a down-regulation of the expression of key carotenoids biosynthetic genes (PSY, PDS, ZDS1, LCY2a, LCY2b, and CHX). However, expression of MEP pathway genes (DXS, HDR1, and GGPPS1) and the carotenoid cleavage dioxygenase, CCD4b1, responsible of the formation of the apocarotenoid β-citraurin, were not substantially affected by dark-grown conditions. The content of abscisic acid (ABA), an end product of the carotenoid pathway, was not affected by the light regime, suggesting that effect of shading on the precursor’s pool is not sufficient to impair ABA synthesis. A moderate increase in total carotenoid and in the expression of biosynthetic genes was observed in mature dark-grown mandarin and orange fruits. Collectively, results suggest that light stimulates carotenoid biosynthesis in the peel of citrus fruits but a light-independent regulation may also operate.

Morphometric and biochemical characterization of old low-chilling pear cultivars (pyrus communis l.) Grown in Tunisia

Fruit quality attributes were studied in eight old pear cultivars grown in a Mediterranean climate in the Centereasternof Tunisia. Fruit quantitative and qualitative morphological parameters, fruit skin color on both sunexposedand shaded fruit sides, and chemical characteristics in both flesh and peel (titratable acidity, TSS, fructose,glucose, sucrose, total sugars, citric and malic acids) were evaluated. A high variability was found in the set of theevaluated pear cultivars. The fruit weight varied from 22.63 g to 63.72 g and firmness varied from 2.78 kg/cm2and 4.78 kg/cm2. ‘Arbi Sidi Bou Ali’ and ‘Arbi Bouficha’ presented the biggest fruits. However, ‘Radsi’ tendedto have the smallest fruits. ‘Jrani’ and ‘Arbi Chiheb’ have shown the lowest values of healthy seeds per fruit.‘Radsi’ pears were the most red-colored fruits, while ‘Jrani’ ‘Arbi Chiheb’ and ‘Arbi Bouficha’ produced greenyellowishfruits. Results showed also that pear fruit flesh had more effective sugars and organic acids comparedto peel for all cultivars. The TSS ranged from14.6° brix to 19.1°Brix in the flesh and from 12 to 17.1°Brix in thepeel. ‘Arbi Chiheb’ was distinguished by the highest malic acid content in both flesh and peel. Titratable aciditywas significantly higher in ‘Arbi Sidi Bou Ali’, ‘Tourki’ and ‘Meski Arteb’ compared to other cultivars. A highcorrelation was found among some pear quality attributes, which could reduce the number of pomological traits.These results would be a guide in the selection of potential cultivars which are used in food industry and freshmarket as well as in breeding programs.

Cluster illumination differentially affects growth of fruits along their ontogeny in highbush blueberry ( Vaccinium corymbosum L.)

Abstract Shading highbush blueberry plants generally leads to a delayed fruit development. Experiments have been performed to study the effects of light on fruit growth independently from the rest of the canopy. Clusters were shaded during different fruit growth periods. The equatorial diameter of the fruits as a function of days after full bloom followed a double-sigmoidal growth pattern, being fitted using a Gompertz II nonlinear mixed model, and absolute growth rates were obtained from each fitted model. Both whole-cycle shaded and second-stage shaded fruits showed a delayed peak in absolute growth curves with respect to both first-stage shaded and whole-cycle unshaded controls. Our results suggest that deficiency of light during the last stage of highbush blueberry fruits may lead to a substantial delay (of about 10–16 days) in harvest as compared with well-illuminated fruits. In order to estimate the contribution of intrinsic fruit photosynthesis to its own growth at different stages, clusters were subjected to girdling on their peduncles at different times. Girdling just before the second-stage resulted in fruits gaining between 35 and 40% of dry weight in comparison with the controls. This suggests that fruit photosynthesis may play a relevant role in fruit growth during the second sigmoidal stage, which in turn may contribute to explain the delayed growth observed in shaded fruits.

Improving photosynthetic performance and some fruit quality traits in mango trees by shading

Excess solar radiation under hot climate can lead to decline in photosynthetic activity with detrimental effects on growth and yield. The aim of this study was to evaluate the use of a transparent plastic roof as shading for diurnal changes in photosynthetic gas exchange, chlorophyll fluorescence, fruit set and quality of mango (Mangifera indica L.) cv. ‘Nam Dok Mai’ growth in the field conditions. Fully expanded leaves were examined either shaded by the plastic roof or sunlit under natural conditions. Leaf temperature and leaf-to-air vapour pressure deficit of the shaded leaves measured on the clear day were lowered compared to those of the sunlit leaves. It resulted in increased stomatal conductance and photosynthetic rates of the shaded leaves compared to those of the sunlit leaves, especially from the morning to midday. Furthermore, the reversible decrease of the maximal quantum yield of PSII was more pronounced in the sunlit leaves than that in the shaded ones. Shading increased the total fruit number; the shaded fruits developed better external color than that of the sun-exposed fruits. Our results indicated that shading could maintain the high photosynthetic activity by reducing stomatal limitations for carbon supply and was effective in alleviating the photoinhibitory damage to PSII during bright and clear days with excessive radiation. Finally, shading could increase the number of fruits and improve mango peel color.

Olive fruit growth, tissue development and composition as affected by irradiance received in different hedgerow positions and orientations

Incident radiation strongly influences fruit development, but little is known regarding the specific responses to the radiation differences found at different canopy heights and orientations in the new intensive hedgerow orchards. We tested the effect of position-determined solar microenvironment on olive fruit size, composition, and cellular development among positions at successive heights along both faces of N–S and E–W oriented olive hedgerows (cv. Arbequina). Total incident irradiance over the fruit growth period at each canopy position was modeled, and the relationships of all fruit parameters to irradiance and amongst each other were tested. Fruit and mesocarp weight and oil increased from canopy base to top and were linearly related to irradiance, while water content showed the opposite pattern, suggesting that priorities for distribution among different sinks are strongly influenced by irradiance level. Similar patterns of fruit size and composition in relation to irradiance were also observed among hedgerow orientations. Endocarp weight and composition varied little among irradiance levels, reflecting the conservative nature of this tissue as an active sink. Greater fruit size, mesocarp weight, and oil in positions of higher irradiance, even when fruit number was higher, indicating that those yield components were primarily affected by source supply and not limited by sink competition. Fruit exposed to light developed larger mesocarp cells than shaded fruit but cell number was not affected, and mesocarp oil content was highly associated with mesocarp cell size.

Differential effects of shading fruit or foliage on the development and composition of grape berries

Grape vines ( Vitis vinifera L. cv. Cabernet Sauvignon) were selectively shaded with polypropylene doth to separate the effects of shading fruit from the effects of shading foliage on berry development and on the accumulation patterns of sugar, anthocyanins, malate, tartrate and potassium in the fruit. Shading the foliage led to both a delay and a decrease in berry growth. Leaf shading also affected the timing and the magnitude of sugar accumulation. Total sugar per berry was reduced more by shading than was sugar concentration because of the simultaneous effect of shading on fruit size. The rate of pre-veraison malate accumulation, the maximum malate content at veraison, and the rate of post-veraison malate loss in the berries were all highest in the fully sun-exposed vines and were progressively lower with increasing foliage shade. Tartaric acid was significantly lower in fruit from heavily shaded vines than in fruit from the more exposed treatments. Leaf shading was also significantly correlated with an increase in potassium concentration in the fruit. At harvest, juice pH was more dosely correlated with the concentrations of tartaric acid and potassium in the berries than with malate content. Grapes from heavily shaded vines had the highest pH. Anthocyanin accumulation in the fruit was affected more by duster shading than by leaf shading. Shaded fruit had significantly less anthocyanin than sun exposed fruit. These results indicate that in addition to a general delay in ripening there were also specific effects of shading on individual components of berry composition, and that the specific effects were different for leaf and duster shading.

Cloning and characterization of the CarbcL gene related to chlorophyll in pepper (Capsicum annuum L.) under fruit shade stress.

Light is an important environmental factor for fruit development and ripening in pepper plant. Fruit bagging is a significant agrotechnology practiced for the illumination regulation of fruits; some previous researches have shown that fruit bagging could improve the appearance and external quality of fruits and cause them to mature early. However, it would decrease the intrinsic qualities of fruits; especially, fruit bagging could decrease the content of capsanthin in peppers. On the basis of these details, fruit bagging was used as the method of fruit shade stress in this study to explore the characteristics and molecular mechanisms of pepper fruit's color change under shade stress. By using cDNA-AFLP under fruit shading, a fragment related to fruit color was obtained. Next, the full-length coding sequence of the gene was cloned from the pepper fruits. Homologous gene alignment confirmed that the gene has high homology with the rbcL gene, named CarbcL. The function of the CarbcL gene was identified through virus-induced gene silencing (VIGS); it was found that the fruit color changed completely from green to red except for some residue of green fleck when CarbcL gene was silenced, and the green color of fruits had not fully faded in the control group and the empty vector group. The combine determination of chlorophyll content showed that CarbcL was involved in the metabolic control of chlorophyll in pepper fruits; subsequently, HPLC was used to determine the content of capsanthin in pepper fruit which the CarbcL gene was silencing, and it was also found that the content of capsanthin decreased appreciably. These results further confirmed that CarbcL gene was involved in the adjustment of chlorophyll and capsanthin.

Fruit shading enhances peel color, carotenes accumulation and chromoplast differentiation in red grapefruit.

The distinctive color of red grapefruits is due to lycopene, an unusual carotene in citrus. It has been observed that red 'Star Ruby' (SR) grapefruits grown inside the tree canopy develop a more intense red coloration than those exposed to higher light intensities. To investigate the effect of light on SR peel pigmentation, fruit were bagged or exposed to normal photoperiodic conditions, and changes in carotenoids, expression of carotenoid biosynthetic genes and plastid ultrastructure in the peel were analyzed. Light avoidance accelerated chlorophyll breakdown and induced carotenoid accumulation, rendering fruits with an intense coloration. Remarkably, lycopene levels in the peel of shaded fruits were 49-fold higher than in light-exposed fruit while concentrations of downstream metabolites were notably reduced, suggesting a bottleneck at the lycopene cyclization in the biosynthetic pathway. Paradoxically, this increment in carotenoids in covered fruit was not mirrored by changes in mRNA levels of carotenogenic genes, which were mostly up-regulated by light. In addition, covered fruits experienced profound changes in chromoplast differentiation, and the relative expression of genes related to chromoplast development was enhanced. Ultrastructural analysis of plastids revealed an acceleration of chloroplasts to chromoplast transition in the peel of covered fruits concomitantly with development of lycopene crystals and plastoglobuli. In this sense, an accelerated differentiation of chromoplasts may provide biosynthetic capacity and a sink for carotenoids without involving major changes in transcript levels of carotenogenic genes. Light signals seem to regulate carotenoid accumulation at the molecular and structural level by influencing both biosynthetic capacity and sink strength.

Roles of the ascorbate–glutathione cycle, pigments and phenolics in postharvest ‘sunscald’ development on ‘Granny Smith’ apples (Malus domestica Borkh.)

Postharvest sunscald on apples is a physiological disorder that develops on the skin during cold storage. The symptoms develop only on sun-exposed sections of the fruit with or without sun-injury and they appear as superficial dark-brown patches. In order to determine the role of different antioxidant systems in sunscald development, fruit with different sun exposures and sun-injury levels on the tree were harvested and stored at 0°C for up to 4 months. Ascorbic acid (AsA), glutathione (GSH), AsA–GSH recycling enzymes activities and transcripts levels, and flavonoids and carotenoid concentrations were monitored monthly. Unexposed fruit (shaded) did not develop sunscald. On sun-exposed sections of the fruit, sunscald incidence increased and appeared closer to harvest, as sunburn severity increased. Total ascorbic acid (AsA) was the highest on fruit with no sunburn symptoms (shaded and sun-exposed), but over 90% of it was in its oxidized form. There were no clear differences for any of the AsA–GSH recycling enzyme activities or transcription levels between sun exposures levels during cold storage.All quercetin glycosides were higher in fruit with sun-injury compared to those sun-exposed or shaded throughout the storage period. In severe sunburned or shaded fruit, quercetin glycosides represented 73% and 10% of total phenolic content, respectively. Quercetin glycosides contents at harvest were highly correlated with sunscald appearance in storage.Sunscald symptoms appearance was associated with lower quercetin glycosides concentration on fruit skin. The results indicate that the AsA–GSH cycle does not play a direct role in ‘sunscald’ development on Granny Smith apples. Instead, quercetin glycosides appear to be directly related with sunscald expression postharvest, i.e. the higher their concentration in the tissue, the faster the accumulation of their brown oxidative products.