Fruit Color Development Research Articles

Transcriptomic and metabolomic profiling reveals the mechanisms of color and taste development in cherry tomato cultivars

Fruit color and taste are important quality characters of cherry tomatoes. The present study analyzed the genes and metabolites in the three cherry tomatoes with different fruit colors (red, green, and yellow) at the maturity stage to characterize the physiological and molecular mechanisms underlying fruit color and taste. Profiling identified 627 compounds grouped into 37 classes and 25,106 uniquely expressed genes in cherry tomato fruit samples. Significant variations were detected in all three cherry tomatoes. In addition, association analysis depicted that the differentially expressed genes and differentially accumulated metabolites were mainly associated with phenylpropanoid biosynthesis, flavonoid biosynthesis, and flavone and flavonol biosynthesis pathways, and carotenoid pathway which are likely to be the key metabolites and genes underlying the differences for colors among the cherry tomato fruits. Overall, these findings revealed the basis of mechanisms underlying fruit color and taste development and provided valuable information for the genetic improvement of cherry tomatoes.

A Fruit Colour Development Index (CDI) to Support Harvest Time Decisions in Peach and Nectarine Orchards

Fruit skin colour is one of the most important visual fruit quality parameters driving consumer preferences. Proximal sensors such as machine vision cameras can be used to detect skin colour in fruit visible in collected images, but their accuracy in variable orchard light conditions remains a practical challenge. This work aimed to derive a new fruit skin colour attribute—namely a Colour Development Index (CDI), ranging from 0 to 1, that intuitively increases as fruit becomes redder—to assess colour development in peach and nectarine fruit skin. CDI measurements were generated from high-resolution images collected on both east and west sides of the canopies of three peach and one nectarine cultivars using the commercial mobile platform Cartographer (Green Atlas). Fruit colour (RGB values) was extracted from the central pixels of detected fruit and converted into a CDI. The repeatability of CDI measurements under different light environments was tested by scanning orchards at different times of the day. The effects of cultivar and canopy side on CDI were also determined. CDI data was related to the index of absorbance difference (IAD)—an index of chlorophyll degradation that was correlated with ethylene emission—and its response to time from harvest was modelled. The CDI was only significantly altered when measurements were taken in the middle of the morning or in the middle of the afternoon, when the presence of the sun in the image caused significant alteration of the image brightness. The CDI was tightly related to IAD, and CDI values plateaued (0.833 ± 0.009) at IAD ≤ 1.20 (climacteric onset) in ‘Majestic Pearl’ nectarine, suggesting that CDI thresholds show potential to be used for harvest time decisions and to support logistics. In order to obtain comparable CDI datasets to study colour development or forecast harvest time, it is recommended to scan peach and nectarine orchards at night, in the early morning, solar noon, or late afternoon. This study found that the CDI can serve as a standardised and objective skin colour index for peaches and nectarines.

ABA Speeds Up the Progress of Color in Developing F. chiloensis Fruit through the Activation of PAL, CHS and ANS, Key Genes of the Phenylpropanoid/Flavonoid and Anthocyanin Pathways.

Phenolic compounds with antioxidant properties have risen in interest due to their benefits for human health. Fragaria chiloensis is a native wild berry species from Chile that develops a white/pink receptacle and white flesh at the ripe stage. Changes in color parameters, anthocyanins, secondary metabolites (phenolics, flavonoids), and total antioxidant capacity were followed during the development and ripening of F. chiloensis fruit. The increment in color ‘a’ index takes place in parallel with anthocyanins rise and the reduction in phenolics, flavonoids, and antioxidant capacity. Good correlations were determined between color development, anthocyanins, and the expression of key phenylpropanoid/flavonoid and anthocyanin pathway genes. To investigate the role of ABA on color development, detached immature fruit (C2 stage) were treated with exogenous ABA and stored at 20 °C. Fruit color development was accelerated by ABA treatment compared to non-treated fruit, and consistent with that, the increment in the accumulation of anthocyanins and transcripts of phenylpropanoid/flavonoid, and anthocyanin pathways genes such as FcPAL, FcCHS, and FcANS were observed. This suggests that ABA promotes transcriptional changes that lead to the color formation on this non-climacteric fruit.

Effect of Elevated Temperature on Tomato Post-Harvest Properties.

The fleshy fruit of tomato (Solanum lycopersicum) is a commodity used worldwide as a fresh or processed product. Like many crops, tomato plants and harvested fruits are susceptible to the onset of climate change. Temperature plays a key role in tomato fruit production and ripening, including softening, development of fruit colour, flavour and aroma. The combination of climate change and the drive to reduce carbon emission and energy consumption is likely to affect tomato post-harvest storage conditions. In this study, we investigated the effect of an elevated storage temperature on tomato shelf life and fungal susceptibility. A collection of 41 genotypes with low and high field performance at elevated temperature, including different growth, fruit and market types, was used to assess post-harvest performances. A temperature increase from 18–20 °C to 26 °C reduced average shelf life of fruit by 4 days ± 1 day and increased fungal susceptibility by 11% ± 5% across all genotypes. We identified tomato varieties that exhibit both favourable post-harvest fruit quality and high field performance at elevated temperature. This work contributes to efforts to enhance crop resilience by selecting for thermotolerance combined with traits suitable to maintain and improve fruit quality, shelf life and pathogen susceptibility under changing climate conditions.

Arachidonic acid treatment combined with low temperature conditioning mitigates chilling injury in cold‐stored banana fruit

SummaryCold‐stored banana fruit is particularly susceptible to chilling injury (CI). Over transportation and storage, CI is a key physiological factor affecting postharvest banana quality. Arachidonic acid (ARA) is considered a signal molecule that elicits stress signalling networks in plants. However, whether exogenous ARA treatment can reduce CI in postharvest fruit remains unknown. This study investigated the effects of a combination of exogenous ARA treatment and low temperature conditioning (LTC) on mitigating CI occurrence. ARA + LTC treatment decreased electrolyte leakage, accumulation of malondialdehyde, H2O2 content, weight loss and occurrence of CI symptoms. This treatment also delayed fruit softening and colour development, and maintained both vitamin C and chlorophyll contents in bananas stored at 0 °C for 36 days. In addition, ARA + LTC treatment significantly increased the activities of ascorbate peroxidase, glutathione reductase, peroxidase, catalase and superoxide dismutase. Concluding, ARA + LTC treatment has the potential to reduce CI in banana fruit during cold storage. This makes it an effective postharvest technique for fruits and vegetables susceptible to CI.

Ethylene Induced by Sound Stimulation Enhances Anthocyanin Accumulation in Grape Berry Skin through Direct Upregulation of UDP-Glucose: Flavonoid 3-O-Glucosyltransferase.

Global warming has resulted in the loss of anthocyanin accumulation in berry skin. Sound stimulation can be used as a potential method for enhancing fruit color development since many plants recognize sound vibration as an external stimulus and alter their physiological status in response to it. Sound stimulation (sine wave sound at 1000 Hz) enhanced anthocyanin accumulation in grape cultured cells and berry skins in field-grown grapevines at the early stage of ripening. The transcription of UFGT and ACO2, which encode the key enzymes in anthocyanin and ethylene biosynthesis, respectively, was upregulated in grape cultured cells exposed to sound stimulation. In contrast, the transcription of MybA1 and NCED1, which encode a transcription factor for UFGT and a key enzyme in abscisic acid biosynthesis, respectively, was not affected by the sound stimulation. A treatment with an ethylene biosynthesis inhibitor, aminoethoxyvinyl glycine hydrochloride, revered the enhancement of anthocyanin accumulation by sound stimulation. As the promoter assay using a GUS reporter gene demonstrated that UFGT promoter was directly activated by the ethylene-releasing compound ethephon, which enhanced anthocyanin accumulation in grape cultured cells, we conclude that sound stimulation enhanced anthocyanin accumulation through the direct upregulation of UFGT by ethylene biosynthesis. Our findings suggest that sound stimulation contributes to alleviating poor coloration in berry skin as a novel and innovative practical technique in viticulture.

Genome-Wide Characterization and Analysis of bHLH Transcription Factors Related to Anthocyanin Biosynthesis in Fig (Ficus carica L.).

The basic helix–loop–helix (bHLH) transcription factor family is the second largest transcription factor family in plants, and participates in various plant growth and development processes. A total of 118 bHLH genes were identified from fig (Ficus carica L.) by whole-genome database search. Phylogenetic analysis with Arabidopsis homologs divided them into 25 subfamilies. Most of the bHLHs in each subfamily shared a similar gene structure and conserved motifs. Seventy-two bHLHs were found expressed at fragments per kilobase per million mapped (FPKM) > 10 in the fig fruit; among them, 15 bHLHs from eight subfamilies had FPKM > 100 in at least one sample. bHLH subfamilies had different expression patterns in the female flower tissue and peel during fig fruit development. Comparing green and purple peel mutants, 13 bHLH genes had a significantly different (≥ 2-fold) expression. Light deprivation resulted in 68 significantly upregulated and 22 downregulated bHLH genes in the peel of the fruit. Sixteen bHLH genes in subfamily III were selected by three sets of transcriptomic data as candidate genes related to anthocyanin synthesis. Interaction network prediction and yeast two-hybrid screening verified the interaction between FcbHLH42 and anthocyanin synthesis-related genes. The transient expression of FcbHLH42 in tobacco led to an apparent anthocyanin accumulation. Our results confirm the first fig bHLH gene involved in fruit color development, laying the foundation for an in-depth functional study on other FcbHLH genes in fig fruit quality formation, and contributing to our understanding of the evolution of bHLH genes in other horticulturally important Ficus species.

Reflective Groundcover Improves Fruit Skin Color in ‘Honeycrisp’ Apples Grown under Protective Netting

In semiarid apple (Malus domestica) growing regions, high temperatures and excessive solar radiation can increase the risk of sunburn development. Protective netting is increasingly used as a cultural practice under these conditions to mitigate fruit sunburn losses. However, fruit skin color development can be negatively affected under protective nets due to the reduction in light availability. Reflective groundcovers have been previously reported to increase fruit color development, particularly in the inner parts of the tree canopy. Here, we compared two types of reflective groundcover: a woven polyethylene fabric and a film material with a grassed control without reflective material under a protective netting installation that reduced photosynthetically active radiation (PAR) by 17%. The experiment was conducted in a semiarid climate on a 5-year-old ‘Cameron Select Honeycrisp’ apple orchard near Quincy, WA. Light penetration into the canopy was measured with a PAR sensor. At harvest, fruit quality, yield, and size were assessed. The use of reflective groundcover between the rows significantly increased reflected PAR into the lower canopy. Moreover, reflective groundcovers significantly increased the amount of fruit with greater than 25% skin red color compared with the control. Reflective groundcover did not affect fruit weight, yield, and fruit number. The use of reflective groundcover under protective netting can increase light penetration into the canopy, thereby improving fruit skin red coloration in apple.

Canopy Spraying of Abscisic Acid to Improve Fruit Quality of Different Sweet Cherry Cultivars

Abscisic acid (ABA) plays a major role in promoting ripening in sweet cherry, a non-climacteric fruit. Exogenous application of ABA has been performed to study fruit ripening and cracking, but this growth regulator is not used for commercial production. To determine the potential of this growth regulator to improve sweet cherry fruit quality, ABA canopy spraying was assayed in four cultivars. Canopy spraying of S-ABA significantly: (1) enhanced sweet cherry fruit color in ‘Glenred’, ‘Lapins’ and ‘Bing’ cultivars, but not in ‘Royal Rainier’ (a bi-colored cultivar), and (2) decreased fruit size and firmness in ‘Lapins’, ‘Bing’ and ‘Royal Rainier’. Seasonally reproducible effects were seen in ‘Lapins’ (mid/late-maturing) but not in ‘Glenred’ (early-maturing). Canopy spraying of nordihydroguaiaretic acid (NDGA) decreased color and increased fruit size in ‘Lapins’, but not in ‘Glenred’. Direct application of ABA on fruits attached to the tree, without application to the foliage, increased ‘Lapins’ fruit color without reducing size. These results suggest a localized fruit response to exogenous ABA application on fruit color development, but that a decrease in fruit size may be due to the effects of exogenous ABA on the tree canopy foliage.

Development of fruit color in Rubus chingii Hu (Chinese raspberry): A story about novel offshoots of anthocyanin and carotenoid biosynthesis

Rubus chingii, is widely distributed in many Asian countries and well known for its medicinal and dietary properties. Diversity of fruit color in raspberry has been attributed to the presence of either anthocyanins or carotenoids. In this study, we investigated anthocyanins and carotenoids, and their biosynthesis by LC–MS/MS. Six anthocyanins mainly consisted of flavanol-anthocyanins while five carotenoids mainly consisted of β-citraurin esters. Flavanol-anthocyanins were produced from an offshoot of the anthocyanin biosynthesis, which started with biosynthesis of flavanols and anthocyanidin by leucoanthocyanidin reductase (LAR)/anthocyanidin reductase (ANR) and anthocyanidin synthase (ANS/LDOX) respectively. β-citraurin esters were produced from cleavage of zeaxanthin and esterification by organic acid, which was an offshoot of the carotenoid biosynthesis. The offshoot started with biosynthesis of zeaxanthin and β-citraurin by carotene β-hydroxylase (CHYB/LUT5) and carotenoid cleavage dioxygenase (CCD) respectively. During fruit ripening, biosynthesis of flavanols and anthocyanins was down-regulated by genes/proteins involved in phenylpropanoid and flavonoid biosynthesis, while biosynthesis of β-citraurin esters was up-regulated by imbalanced expression of genes/proteins involved in β,β-ring and β, ε-ring hydroxylation. Thus, β-citraurin esters, instead of anthocyanins imparted reddish color to the ripe fruit. These pigments and their biosynthesis in R. chingii are totally different from what occurs in other raspberry species.

ABA influences color initiation timing in P. avium L. fruits by sequentially modulating the transcript levels of ABA and anthocyanin-related genes

In sweet cherry, as in most non-climacteric species, abscisic acid (ABA) plays a major role in the control of fruit ripening and color development. Although the ABA treatment of sweet cherry fruits has been reported to upregulate anthocyanin pathway-related genes or ABA pathway-related genes, the temporality of molecular and physiological events occurring during color development and the ABA control of these events during the color initiation are lacking in this species. In this work, we analyzed variations in the Index of Absorbance Difference (IAD), a maturity index, and total anthocyanins along with changes in transcript abundance of ABA and anthocyanin pathway-related genes, from light green to red fruit stages. PavNCED1 and ABA signaling pathway-related genes upregulated when fruits transitioned from light green to pink stage, whereas anthocyanin pathway-related transcripts increased from pink to the red stage, together with increases in the anthocyanin content and IAD, suggesting sequentiality in molecular and physiological events during color development. Additionally, ABA applied at color initiation in planta advanced IAD, increased anthocyanin content, and yielded darker fruits at harvest. These changes were accompanied by changes in the transcript accumulation of ABA and anthocyanin pathway-related genes. This in planta treatment of sweet cherry fruits with ABA confirms that ABA is a central player in the control of color initiation in sweet cherries, associated with the transcript accumulation of genes involved in ABA homeostasis and signaling, which is followed by the up-regulation of anthocyanin pathway-related genes and color development.

Exogenous Application of ABA and NAA Alleviates the Delayed Coloring Caused by Puffing Inhibitor in Citrus Fruit

Combined spraying of gibberellin (GA) and prohydrojasmon (PDJ) was an effective method to reduce peel puffing in Satsuma mandarins. However, in the GA-and-PDJ combined treatment, fruit color development was delayed during the ripening process. In the present study, to improve the coloration of the GA and PDJ-treated fruit, the effects of exogenous application of 1-naphthaleneacetic acid (NAA) and abscisic acid (ABA) on chlorophyll and carotenoid accumulation were investigated. The results showed that both ABA and NAA treatments accelerated the color changes from green to orange in the GA and PDJ-treated fruit during the ripening process. With the NAA and ABA treatments, chlorophylls contents were decreased rapidly, and the contents of β,β-xanthophylls were significantly enhanced in the GA and PDJ-treated fruit. In addition, gene expression results showed that the changes of the chlorophyll and carotenoid metabolisms in the NAA and ABA treatments were highly regulated at the transcriptional level. The results presented in this study suggested that the application of NAA and ABA could potentially be used for improving the coloration of the GA and PDJ-treated fruit.

Potential of Aloe vera gel coating for storage life extension and quality conservation of fruits and vegetables: An overview.

Aloe vera (ALV) with its unique nutritional profile is being used for food, health, and nutraceutical industries globally. Due to its organic nature, ALV gel coating has created lot of interest for exploring its potential in extending the shelf and storage life of fresh produce. ALV gel coating plays imperative role in delaying fruit ripening by lowering ethylene biosynthesis, respiration rate, and internal metabolic activities associated with fruit softening, color development, enzymatic browning, and decay. ALV gel coating reduces the microbial spoilage due to its antifungal properties and maintains visual appearance, firmness, sugar: acid ratio, total antioxidants, and phenolic contents with conserved eating quality. ALV coated fruits and vegetables showed reduced weight loss, superoxide ion ( ), hydrogen peroxide (H2 O2 ), ion leakage, and soluble solids content and exhibited higher acidity, anthocyanins, ascorbic acid, catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX) activities. It also delayed the enzymatic browning by inducing peroxidase (POD) activity during storage. Recent local studies also revealed that ALV gel coating markedly conserved higher consuming quality and extended storage period (>1.34-fold) of different fruits and vegetables. Overall, Aloe vera gel coating alone or in combination with other organic compounds has shown great potential as a food-safe and eco-friendly coating for maintaining the quality of fruits and vegetables over extended period and reducing postharvest losses in the supply chain. PRACTICAL APPLICATIONS: ALV gel is a plant-based natural coating of eco-friendly nature. The present review summarizes the updated information of ALV gel coating application, methods of extraction, combinations with other postharvest coatings, and its impact on quality of various fruits and vegetables. It also provides future insights for the development of commercially applicable ALV gel coating protocols through simulation studies. So, being a natural coating, ALV gel has tremendous potential to be used in fruit and vegetable industries around the globe.

Effect of individual cluster wrapping on colour development and fruit quality of flame seedless grapes (Vitis vinifera L.)

An experiment was conducted to ascertain the effect of individual fruit wrapping on fruit quality and colour development of Flame Seedless variety of grapes during 2018–19 fruiting seasons. Uniform size clusters of Flame Seedless were bagged with white colour and red colour non-woven bags, butter paper bags and LDPE sheets at 40 per cent colour break stage during first of June. At time of attaining full colour, fruits were harvested from all the replication during morning hours and taken for analysis.

Transcriptome profiling provides insights into the fruit color development of wild Lycium ruthenicum Murr. from Qinghai-Tibet Plateau.

Lycium ruthenicum Murr. is an important ecological and economic species in the Qaidam Basin of Qinghai-Tibet Plateau. Its black fruits (BF) are rich in anthocyanins, which have health-promoting properties for humans and thus provide nutritional benefits for this plant. Although the fruit quality of natural white fruit (WF) is affected by the disappearance of pigmentation in phenotypes, this phenomenon provides an opportunity to unravel the complex color metabolic networks. In this study, anthocyanin profiling confirmed that WF was formed due to anthocyanin loss. Transcriptome analysis of BF and WF revealed 101,466 unigenes, 261 of which were identified as the putative homologs of color-related genes in other species. Genes encoding the enzymes involved in flavonoid biosynthesis were also identified systematically. The structural gene expression levels of chalcone synthase (CHS), chalcone isomerase (CHI), flavonoid 3'5'-hydroxylase (F3'5'H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS), and anthocyanidin 3-O-glucosyltransferase (UFGT) were highly similar and significantly positively correlated with anthocyanin accumulation rate in BF. In particular, F3'5'H, UFGT, ANS, and DFR expression levels in BF were 2391, 119, 96, and 85 times higher than those in WF at S3 (35days after anthesis), respectively. This result strongly suggests that the low expression of these genes in WF is responsible for the anthocyanin loss. Meanwhile, the expression patterns of the anthocyanin regulatory genes were also investigated by qRT-PCR. Mass sequencing data were obtained and annotated by deep sequencing and provided a platform for future function and molecular biological research on L. ruthenicum Murr.

RNA-sequencing based gene expression landscape of guava cv. Allahabad Safeda and comparative analysis to colored cultivars

BackgroundGuava (Psidium guajava L.) is an important fruit crop of tropical and subtropical areas of the world. Genomics resources in guava are scanty. RNA-Seq based tissue specific expressed genomic information, de novo transcriptome assembly, functional annotation and differential expression among contrasting genotypes has a potential to set the stage for the functional genomics for traits of commerce like colored flesh and apple color peel.ResultsDevelopment of fruit from flower involves orchestration of myriad molecular switches. We did comparative transcriptome sequencing on leaf, flower and fruit tissues of cv. Allahabad Safeda to understand important genes and pathways controlling fruit development. Tissue specific RNA sequencing and de novo transcriptome assembly using Trinity pipeline provided us the first reference transcriptome for guava consisting of 84,206 genes comprising 279,792 total transcripts with a N50 of 3603 bp. Blast2GO assigned annotation to 116,629 transcripts and PFam based HMM profile annotated 140,061 transcripts with protein domains. Differential expression with EdgeR identified 3033 genes in Allahabad Safeda tissues. Mapping the differentially expressed transcripts over molecular pathways indicate significant Ethylene and Abscisic acid hormonal changes and secondary metabolites, carbohydrate metabolism and fruit softening related gene transcripts during fruit development, maturation and ripening. Differential expression analysis among colored tissue comparisons in 3 cultivars Allahabad Safeda, Punjab Pink and Apple Color identified 68 candidate genes that might be controlling color development in guava fruit. Comparisons of red vs green peel in Apple Color, white pulp vs red pulp in Punjab Pink and fruit maturation vs ripening in non-colored Allahabad Safeda indicates up-regulation of ethylene biosynthesis accompanied to secondary metabolism like phenylpropanoid and monolignol pathways.ConclusionsBenchmarking Universal Single-Copy Orthologs analysis of de novo transcriptome of guava with eudicots identified 93.7% complete BUSCO genes. In silico differential gene expression among tissue types of Allahabad Safeda and validation of candidate genes with qRT-PCR in contrasting color genotypes promises the utility of this first guava transcriptome for its potential of tapping the genetic elements from germplasm collections for enhancing fruit traits.

Anthocyanin Accumulation and Color Development in Seedless Barberry (Berberis vulgaris L.) Fruits: The Role of Altitude and Sun Light - the Preliminary Results

ABSTRACT The present research was conducted to investigate the effect of direct sun-light on color development of seedless barberry fruit. The selected orchards were in different locations (with different altitude). On some trees, some inflorescences were chosen to cover as bagged (excluded from direct sun-light). Some cases also used as non-bagged. Bagging was done in different times during growing season. Results showed that in all regions, day temperatures were higher than 20°C, and night was lower than 30°C. The lowest difference of day-night temperatures observed in Marvak. Bagging showed a significant effect on anthocyanin (ant), hue angle (h*), lightness and redness (a*). Bagging time significantly influenced chroma (C*) and b/a values. Ant, C*, a*, and a/b values significantly affected by location characteristics specifically altitude, and the highest ant and a* value observed in Marvak. In all locations, the highest value of ant and h* observed with not-bagged fruits. The highest value of a* obtained in not-bagged fruits. It is concluded that direct sun is needed for color development of barberry fruits, however, night-cool temperatures also are important for anthocyanin accumulation of this fruit.

Using sap flow data to assess variations in water use and water status of apple orchards of varying age groups in the Western Cape Province of South Africa

No accurate quantitative information currently exists on how water use of apple (Malus domestica) orchards varies from planting to full-bearing age, leading to poor irrigation and water allocation decision making. This study sought to address this knowledge gap by investigating how the water use and tree water status vary with canopy cover, cultivar, and climatic conditions in 12 orchards growing in prime apple-producing regions in South Africa. The orchards were planted to the Golden Delicious/Golden Delicious Reinders cultivars which are widely planted in South Africa and the Cripps’ Pink/Cripps’ Red/Rosy Glow which are high-value late-season cultivars. The performance of two transpiration reduction coefficients, one based on sap flow (Ksf) and the other based on soil water depletion (Ks) (FAO approach) were evaluated against the midday stem water potential (MSWP) in all the orchards. While canopy cover had a clear effect on the whole-tree sap flow rates, there were no significant differences in the transpiration per unit leaf area among the cultivars. The daily average sap flux density under unstressed conditions was highest (~284 cm3∙cm-2) in the medium canopy cover orchards (30–44% fractional cover), followed by the mature orchards (~226 cm3∙cm-2), and was lowest in the young orchards (~137 cm3∙cm-2). Canopy cover rather than growing season length had a greater effect on seasonal total water use. Peak daily orchard transpiration ranged from 1.7 mm for young Golden Delicious Reinders trees to 5.0 mm in mature Golden Delicious trees that were maintained with large canopies to reduce sunburn damage to the fruit. For the red cultivars, the peak daily transpiration ranged from 2.0 to 3.9 mm, and the mature trees were maintained with less dense canopies to facilitate the development of the red fruit colour. The less dense canopies on the red cultivars had water-saving benefits since the seasonal total transpiration was lower relative to the Golden Delicious cultivar. The sap flow derived stress coefficient was strongly correlated to the MSWP (R2 ~ 0.60–0.97) in all the orchards while Ks was not able to detect plant stress due to over-irrigation.

Using sap flow data to assess variations in water use and water status of apple orchards of varying age groups in the Western Cape Province of South Africa

No accurate quantitative information currently exists on how water use of apple (Malus domestica) orchards varies from planting to full-bearing age, leading to poor irrigation and water allocation decision making. This study sought to address this knowledge gap by investigating how the water use and tree water status vary with canopy cover, cultivar, and climatic conditions in 12 orchards growing in prime apple-producing regions in South Africa. The orchards were planted to the Golden Delicious/Golden Delicious Reinders cultivars which are widely planted in South Africa and the Cripps’ Pink/Cripps’ Red/Rosy Glow which are high-value late-season cultivars. The performance of two transpiration reduction coefficients, one based on sap flow (Ksf) and the other based on soil water depletion (Ks) (FAO approach) were evaluated against the midday stem water potential (MSWP) in all the orchards. While canopy cover had a clear effect on the whole-tree sap flow rates, there were no significant differences in the transpiration per unit leaf area among the cultivars. The daily average sap flux density under unstressed conditions was highest (~284 cm3∙cm-2) in the medium canopy cover orchards (30–44% fractional cover), followed by the mature orchards (~226 cm3∙cm-2), and was lowest in the young orchards (~137 cm3∙cm-2). Canopy cover rather than growing season length had a greater effect on seasonal total water use. Peak daily orchard transpiration ranged from 1.7 mm for young Golden Delicious Reinders trees to 5.0 mm in mature Golden Delicious trees that were maintained with large canopies to reduce sunburn damage to the fruit. For the red cultivars, the peak daily transpiration ranged from 2.0 to 3.9 mm, and the mature trees were maintained with less dense canopies to facilitate the development of the red fruit colour. The less dense canopies on the red cultivars had water-saving benefits since the seasonal total transpiration was lower relative to the Golden Delicious cultivar. The sap flow derived stress coefficient was strongly correlated to the MSWP (R2 ~ 0.60–0.97) in all the orchards while Ks was not able to detect plant stress due to over-irrigation.

EFFECTS OF DIFFERENT MATURITY STAGES ON THE QUALITY OF PURPLE PASSION FRUIT

Fruit colour development and shrivelling are one of the major concerns of Vietnamese passion fruit industry as it reduces the appearance and downgrades fruit quality. The effects of colour stages were determined in purple passion grown in Gia Lai province, Vietnam. Immediately after harvesting, fruits were transported to the laboratory in Ho Chi Minh City and stored at 20 ºC. Data showed that different maturity stages, viz., skin colour development stages of purple passion fruit significantly affected the quality including colour development and chemical properties.