Search

Poor rind colour in cv. M7 Navel (Citrus sinensis L. Osbeck) at harvest time severely affects the profits of the growers in Western Australia. The effects of the preharvest spray application of different concentrations (0, 1.25, 2.5, 5.0 and 7.5 mM) of methyl jasmonate (MJ) on the rind colour development and fruit quality of M7 Navel were investigated at 6 or 3 weeks before anticipated harvest (WBAH) during 2015 and 2016. The preharvest spray application of MJ (5.0 or 7.5 mM) resulted in enhanced rind colour, reduced hue angle (ho) angle (55.7, 54.3) as well as increased citrus colour index (CCI) (11.0, 12.0) and total carotenoid levels (35.3, 58.3 mg kg-1) of flavedo, respectively in M7 Navel, during 2015 and 2016. During 2015, comparatively higher levels of total carotenoid (40.4 mg kg-1) were recorded when MJ was applied at 3 WBAH as a single spray. However, the time of MJ application did not influence hue angle (h°) and CCI. In 2015, all the preharvest MJ treatments except (1.25 mM) exhibited reduced fruit firmness. Furthermore, soluble solids concentration (SSC) in the fruit juice was reduced after MJ treatment. All the MJ treatments showed reduced levels of total sugars and organic acids in the juice, during 2015. In conclusion, MJ (5.0 or 7.5 mM) reduced h° but increased the total carotenoids levels and CCI in the flavedo of M7 Navel orange, when applied as a preharvest spray at 3 WBAH

This research was conducted during seasons 2018 & 2019 on nine-years-old Washington navel orange trees. These trees were grafted on Sour orange rootstock, planted at 5 x 5 meters apart, under surface irrigation conditions, in a private orchard at Manzala village, Toukh region, Qalubia Governorate, Egypt. The seven treatments were used for comparison as follows: T1-100% of chemical NPK (NPK fertilization program adopted at 5, 3 and 1 kg/tree from (NH4)2SO4, superphosphate and K2SO4, respectively) according to the Ministry of Agriculture Recommendation (Control or recommended doses RD). T2-RD+Calcium boron 2 cm3 /L; T3-RD+Calcium boron 3 cm3/L; T4-RD+Carpox-K 1g/L; T5-RD+Carpox-K 1.5g/L; T6-RD+Calcium boron 2 cm3 /L +Carpox-K 1g/L, and T7-RD+Calcium boron 3 cm3/L +Carpox-K 1.5g/L. The main goal of this investigation was directed towards increasing Washington navel orange fruit quality. The obtained data revealed that all investigated treatments increased fruit quality parameters (physical and chemical properties). However, T7- RD + Calcium boron 3 cm3 /L + Carpox-K 1.5g/L was statistically superior. On the contrary, T1- Control or recommended doses (RD) ranked statistically the lowest treatment in this concern. From the obtained results, It can be concluded that the use of RD+ Calcium boron 3 cm3 / L + Carpox-K 1.5g / L or RD+ Calcium boron 2 cm3/ L + Carpox-K 1g / L could be safely recommended under similar environmental and horticultural practises adopted in this experiment.

Essential oil (EO) of navel orange (Citrus sinensis) has biological and pharmaceutical properties such as antimicrobial and anticancer. Geographical regions play an important role in physiological ...

Thisstudy was carried out in Scale Insects and Mealybugs Department, Plant Protection Research Institute, Sharkia Branch, ARC, Egypt from May to September 2017 on navel orange leaves infested with the Parlatoria black scale, Parlatoria ziziphi (Lucas) to calculate economic threshold and economic injury levels depending on the loss of leaves chlorophyll content. Simple correlation and partial regression were calculated between numbers of insect and chlorophyll loss percentage in infested and uninfested units (inch2). Positive highly significant correlation was recorded between numbers of insect and percentage of chlorophyll loss. Chi-square (X2) was used to calculate economic threshold and economic injury levels of P. ziziphi that causes economic damage in disk chlorophyll content which were 9 and 14 individuals per inch2, respectively.

Two famous Citrus rootstocks sour orange (C. aurantium.) and volkamer lemon (C. volkamariana.) were tested as interstocks at the stage of transplant production to investigate their mutual effects on the scion growth characteristics, mineral content, carbohydrates, total indols and phenols from side; and rootstock growth traits. nitrogen content, carbohydrates, indols and phenols from the other side. Also the results indicated that Navel orange budded on C. volkamariana grafted on C. volkamariana achieved significantly the highest scion height, root length, leaf number. The highest content of N, P, K, Mg, Fe, Zn, Mn and total phenols in scion stem. Moreover, the mentioned treatment gained the highest significant carbohydrates in roots.

ve seasons, 2012 and 2013 in a private orchard in Barshom vallage located at El-Kalubia Governorate Egypt. Washington Navel Orange trees (Citrus Sinensis) budded on sour orange rootstock (Citrus aurantium, L.) were 7- years- old and planted at 5 x 5 meters under basin irrigation system. This investigation aimed to study the effect of selenium (Se) levels (0, 20, 40, 80 and 160 ppm) as foliar spray on growth, yield, fruit quality, leaf mineral content and enzymes activity of Washington Navel orange trees. The obtained data showed that, selenium had a significant promotive effect on growth, yield, fruit quality, leaf mineral content and enzymes activity of Washington Navel orange trees. Results indicated that treatment of Se at 40 ppm gave the highest significant results, whereas, treatment 160 ppm gave the highest fruit selenium content.

Changes in non-traditional indices of maturity, such as flavonoids and volatile compounds, during maturation were studied in Navel orange. Navel oranges were obtained at four stages of maturation, and non-volatile and volatile compounds in the peel and juice were analysed using liquid chromatography coupled with a quadrupole time-of-flight detector (LC-QTOF/MS) and gas chromatography with mass spectrometry and a flame ionisation detector (GC-MS/FID), respectively. Twenty-eight non-volatile and 62 volatile compounds in the peel as well as 22 non-volatile and 11 volatile compounds in the juice were found to have significant changes (p 0.05) in abundances during maturation. Notably, most flavonoids (e.g. narirutin) and limonoids (e.g. nomilin) showed decreasing abundances during maturation. For volatile compounds, majority of detected alcohols peaked in abundances during middle maturation stages, while almost all detected aldehydes peaked at full maturity. Most terpenes peaked at earlier maturation stages in juice extracts compared to peel oil extracts. This comprehensive study could facilitate selection of Navel oranges for the extraction of valuable bioactive or flavour contributing compounds that are of interest to fragrance, flavour and nutraceutical industries.

Ripe navel orange has abundant amounts of phenolic compounds. Few studies monitored changes in these compounds during ripening. In this study, the effects of navel orange maturation on dynamic changes in antioxidant activity, total phenolic content (TPC), total flavonoid content (TFC) and phenolic acids were investigated. Five growth stages of navel orange were studied, and nine phenolic acids were detected via high performance liquid chromatography-triple quadrupole mass spectrometry (HPLC-QQQ-MS). Results showed that antioxidant activity, TFC and TPC decreased gradually with fruit ripening. The concentrations of most phenolic acids also declined during fruit maturation, except for free fractions of sinapic acid and bound fractions of ferulic and caffeic acids. Ferulic acid was the most dominant of all phenolic acids at all growth stages. Partial least-squares showed significant differences among fruits of different maturities. A significant correlation between antioxidant capacity, TPC, TFC and some phenolic acids was found.

This study investigated the effects of cross-pollination by ‘Murcott’ tangor on the fruit quality of ‘Qicheng52’ navel orange, including the physicochemical properties, bioactive compounds and antioxidant capacities. There were no significant differences on the fruit weight, juice yield and pH value of juice between self- and cross-pollinated fruits. However, cross-pollination could significantly improve the fruit quality of ‘Qicheng52’ fruits by increasing the total soluble solid content from 11.12 ± 1.02 °Brix to 13.86 ± 1.17 °Brix. The results of high performance liquid chromatography analysis of three sugar components indicated that the increase of total sugar was mainly contributed by the increase of fructose and sucrose. Cross-pollination exhibited no effect on the flavonoids content, while the total phenolics content was increased from 210.09 ± 18.55 mg/L to 298.25 ± 29.10 mg/L, which contributed to the higher antioxidant capacity in the cross-pollination fruit juice.

The current study aimed to examine the in vitro and in vivo antifungal potential of pinocembrin-7-glucoside (P7G). P7G is an antifungal flavanone glycoside isolated from Ficus hirta Vahl. fruit against Penicillium italicum, a causative pathogen of blue mold disease in citrus fruit, and this study elucidates its possible action mechanism. P7G had a prominent mycelial growth inhibitory activity against P. italicum, with an observed half maximal effective concentration, minimum inhibitory concentration and minimum fungicidal concentration of 0.08, 0.2, and 0.8 g/L, respectively. The data from the in vivo test show that P7G significantly reduced blue mold symptoms and disease development of P. italicum in artificially inoculated &ldquo, Newhall&rdquo, navel orange. Compared to the control, increases in the cell membrane permeability of P. italicum supernatant and decreases in the intracellular constituent (e.g., soluble protein, reducing sugar, and total lipid) contents of P. italicum mycelia were identified, supporting scanning electron microscopy and transmission electron microscopy observations. Furthermore, a marked decline in both chitin and glucanase contents of P. italicum mycelia treated with P7G was induced by increasing its related degrading enzyme activities, suggesting that the cell wall structure was destroyed. The current study indicated that P7G may be a novel alternative for reducing blue mold by suppressing mycelial growth of P. italicum via a cell membrane/wall-targeting mechanism.

This investigation was carried out during two successive seasons 2013 and 2014 on fruits of Washington Navel orange (Citrus sinensis L.). The experiment was conducted to evaluate the influence of some environmentally safe matural products to improve the storability of Navel orange (citrus sinensis) fruits during 2013 and 2014 seasons, Jojoba oil (1,3,5)%, castor oil (0.5, 1,2)%, yeast (1,2,3)%, seaweed (1,2,3)%, hot water (45ᵒC and commercial wax were used for proposed study, After the application of the treatments on the fruits, fruits were stored at a temperature of 5°±1 C and 90%±5 of relative humidity for 60 days, physical characteristics (weight loss%, decay% and the peel's thickness of the crust) and chemical properties (total phenols) were determined. Results indicated that, castor oil (2 and 1)% and jojoba oil 5% reduced the deterioration in weight loss%, decay%, peel thickness, and phenols content, compared to the content was obtained in control. So the results show that, coating orange fruits with castor oil (1, 2)% and jojoba oil (5)% had the most effective in improve the storability of orange fruits Navel Orange (Citrus sinensis L.).

Poor fruit colour development at harvest in early maturing M7 sweet orange cultivar causes economic losses to the growers. The responses of different concentrations (50, 100, 200, 300 or 500 mgL−1) of abscisic acid (S-ABA) and its biosynthesis inhibitor nordihydroguaiaretic acid (NDGA) (0.01, 0.02, 0.04 mM) at pre-harvest stage (6 or 3 weeks before anticipated harvest) on peel colour development particularly from yellow to deep orange and on the fruit quality of M7 were studied during 2015 and 2016 in Western Australia. S-ABA treatments during both years irrespective of the concentrations applied exhibited significantly lower hue angle (h°) with enhanced citrus colour index (CCI) and higher levels of total carotenoids in the flavedo during 2015 and 2016. Spray application of S-ABA (300 and 500 mg L−1) resulted in higher level of total carotenoids (35.0 and 71.5 mg kg−1) in the flavedo during 2015 and 2016. A single spray application of S-ABA applied at 6 weeks before anticipated harvest (WBAH) showed higher mean CCI (10.1) and level of total carotenoids (37.6 mg kg−1) as compared to its single application at 3 WBAH and double spray at 6 WBAH followed by 3 WBAH in 2015. However, nordihydroguaiaretic acid (NDGA) restricted colour development indicated by higher h° and reduced CCI with lower levels of total carotenoids in the flavedo during 2015. S-ABA treatments exhibited significantly reduced total organic acids in the juice, whilst total sugars were not affected by any of the treatments. S-ABA treatments (200 and 300 mg L−1) showed increased SSC/TA ratio (12.8%) as a result of reduction in total acidity (TA) (0.96%). In conclusion, pre-harvest spray application of S-ABA promoted fruit colour development from yellow to deep orange, indicated by reduced h° and increased CCI as well as the levels of total carotenoids in the flavedo of M7 Navel orange. Promotion of fruit colour development (yellow to deep orange) with the pre-harvest application of S-ABA and its down regulation with the application of ABA biosynthesis inhibitor (NDGA) suggested the involvement of S-ABA in flavedo colour development in M7 Navel orange fruit.

Many citrus varieties are hybridized to improve their quality and to overcome the effects of climate change. However, there is limited information on the effect of the chemical profiles of hybrid varieties on their quality. In this study, we analyzed 10 citrus varieties and evaluated the correlation with their general characteristics and antioxidant activities. Chemical profiles, including the contents of sugars, organic acid compounds, flavonoids, limonoids, and carotenoids, which are related to taste, color, and health benefits, were significantly different depending on the citrus varieties, leading to different antioxidant capacities and general quality parameters. Based on these data, the correlations were investigated, and 10 citrus varieties were clustered into four groups—Changshou kumquat and Jeramon (cluster I), Setoka (cluster II-1), Natsumi, Satsuma mandarin, and Navel orange (cluster Ⅱ-2), Kanpei, Tamnaneunbong, Saybyeolbong, and Shiranui (cluster II-3). Moreover, a metabolomic pathway was proposed. Although citrus peels were not analyzed and the sensory and functional qualities of the citrus varieties were not investigated in this study, our results are useful to better understand the relationship between citrus quality and metabolite profiles, which can provide basic information for the development and improvement of new citrus varieties.

Vacuum microwave drying (VMD) technique was applied for drying fresh navel orange peel (NOP) under different vacuum degrees including 0, 25, 45, 65, and 85 kPa. Compared with the traditional hot-air drying (HAD), the drying time of VMD was remarkably reduced by 90.7–94.7%. In addition, the drying time had a negative correlation to the vacuum degree, the drying time at 85 kPa was only 5.3% of HAD. The extraction yield of VMD pectin was significantly higher than that of HAD. Comparing to HAD, the extracted pectin by VMD exhibited an increase in the degree of methoxylation, but a decline in the average molecular weight and apparent viscosity. Moreover, the VMD can promote pectin adsorption capacities to the Pb2+ with the adsorption mechanism of the pseudo-second-order kinetic model. These findings indicated that VMD is a powerful, efficient, time-saving technology for drying fresh NOP and assisting extraction of pectin from NOP.

This study was carried out in lath house of the Department of Horticulture and Landscape Engineering - College of Agriculture - Tikrit University, during the season 2020-2021, as a factorial experiment by spraying with three levels of the growth regulator Brassinolide (BL) which are 0.00, 0.015, 0.025 Mg.L−1 and spraying with nutrient solution PRO-SOL (M) at three concentrations of.000, 200,400. Mg.L−1 to determine the effect of the growth regulator Brassinolide and the nutrient solution PRO-SOL in increasing the chemical content of some nutrients for the two types of navel orange V1 and blood orange V2. The results showed that blood orange V2 was significantly superior to the cultivar Navel V1 in the leaf area amounted to 2991 cm2, the percentage of dry matter in the leaves was 35.39% and the percentage of mineral elements in the leaves was %N, 1.619 %K, 1.37%P, 0.204,. And the best concentration Of Brassinolide 0.025 Mg.L−1 with a concentration of PRO-SOL400 Mg.L−1 has increased the dry matter percentage, leaf area and chemical content of elements for the navel orange variety V1, and the concentration of Brassinolide 0.015 Mg.L−1 with a concentration of PRO-SOL 400 mg.L-1 has increased the dry matter percentage, leaf area and chemical content of elements for blood orange variety V2.

A novel biological treatment of staying with commercially mature apple fruits was proposed to promote the peel coloration of ‘Newhall’ navel orange fruit (Citrus sinensis Osbeck), which could conduce to the formation of uniform orange red peel color. At 15 days after treatment (DAT), the staying with apple (SWA) treatment led to a nearly 4-fold increase in the total carotenoid content compared with the control. Specifically, the red color apocarotenoid β-citraurin showed the highest degree of enhancement (~6 fold) under SWA treatment. Simultaneously, the expression level of β-citraurin biosynthetic gene carotenoid cleavage dioxygenase 4b (CCD4b) was dramatically induced (about 35 folds). Furthermore, SWA had the same effect of promoting coloration and obviously alleviate calyx senescence of citrus fruit compared with ethylene treatment. In conclusion, SWA treatment is a potential environment-friendly and recyclable postharvest technology to improve peel color and maintain fruit freshness for citrus.

In this study, single factor experiment and orthogonal experiment were used to study the extraction effect of carotenoids from navel orange in southern Jiangxi Province assisted by ultrasonic technology. The experimental results showed that when hexane: ethanol=1:1 as the extraction agent, liquid to solid ratio of 1:30, extraction time of 8 min, ultrasonic power of 250 W, extraction temperature of 25°C, extraction times of 4 times, the best extraction effect of carotenoids from Gannan navel orange was obtained.

Background Transcriptome and proteome analyses on fruit pulp from the blood orange ‘Zaohong’ and the navel orange ‘twenty-first century’ were performed to study Citrus sinensis quality-related molecular changes during consecutive developmental periods, including young fruit, fruit-coloring onset and fruit delayed-harvest for two months, during which fruit remained on the trees. Results The time-course analysis for the fruit developmental periods indicated a complex, dynamic gene expression pattern, with the numbers of differentially expressed genes (DEGs) between the two cultivars being 119, 426 and 904 at the three continuous stages tested during fruit development and ripening. The continuous increase in total soluble solids over the course of fruit development was correlated with up-regulated sucrose phosphate synthase (SPS) transcription levels in both cultivars. Eleven differentially expressed genes between the two cultivars involved in the flavonoid pathway were significantly enriched at the onset of the fruit-coloring stage when anthocyanins were detected in blood orange alone. Among 5185 proteins, 65 up-regulated and 29 down-regulated proteins were co-expressed with their cognate mRNAs with significant transcription and protein expression levels when the fruits from the two cultivars were compared at the fruit delayed-harvest stage. Additionally, important genes participating in the γ-aminobutyric acid (GABA) shunt were activated in blood orange at two significant expression levels in the fruit delayed-harvest stage. Thus, organic acids in fruit continuously decreased during this stage. Conclusions This research was the first to provide a more comprehensive understanding of the differentially expressed genes involved in anthocyanin, sucrose and citrate metabolism at the transcriptome and proteome levels in C. sinensis, especially during the fruit delayed-harvest stage. Electronic supplementary material The online version of this article (10.1186/s12864-017-4366-2) contains supplementary material, which is available to authorized users.

Understanding the composition and content of carotenoids in red-flesh navel orange "Cara Cara" cultivated in different regions is valuable for its nutrition assessment and fruit processing control. Herein, the carotenoids of "Cara Cara" fruits, harvested from five typical citrus growing regions of China, were identified and quantified by HPLC-DAD coupled with HPLC-DAD-APCI-MS/MS. In saponified extracts, 19 free carotenoids including 8 carotenes and 11 xanthophylls were identified. In unsaponified extracts, 83.83-93.83% xanthophylls were esterified and 19 esters were inferred, with the 9-cis-violaxanthin ester confirmed as the dominant component. The carotenoid contents showed difference among the "Cara Cara" fruits from different growing regions, which might be attributed to the local environmental conditions, and the temperature was found directly correlated with total carotenoids content of "Cara Cara". The data obtained in this study will facilitate the nutritional evaluation of "Cara Cara" and provide beneficial guidance for fruit processing.

Nutrient deficiency may be a reason for citrus decline in many countries. In the current investigation, soil and leaf samples of 63 Washington Navel orange orchards in arid lands of southern Iran (...

This study aimed to provide a theoretical basis for adopting suitable cultivation measures to tackle calcium (Ca) deficiency in citrus leaves. The Newhall navel orange (Citrus sinensis Osbeck) canopy was sprayed with 20.0 mmol L−1 of Ca(NO3)2 during physiological fruit drop period, fruit expanding period, and fruit maturing period on 30, 90, and 210 days after full bloom (DAFB), respectively, and its effects on leaf gas exchange parameters and leaf mineral nutrition and fruit quality were analyzed. The results showed that: (1) The photosynthetic rate (ACO2) at 9:00 a.m. and 16:00 p.m. of fruit expanding period with 30 and 90 DAFB Ca(NO3)2 treatments slightly or significantly improved mainly by decreasing stomatal limitation and nonstomatal limitation, respectively. (2) Compared with control (CK), the Ca concentration in leaves with 30, 90, and 240 DAFB Ca(NO3)2 treatments increased by 127.16, 97.53, and 33.33%, respectively, and the leaf magnesium concentration also increased by more than 32.26%. However, Ca(NO3)2 canopy spraying on 30 DAFB significantly reduced the leaf potassium concentration, by 22.14% compared with CK. (3) Ca(NO3)2 canopy spraying on 30 DAFB decreased the second fruit drop rate by 30.55% and increased the weight per fruit by 25.04%, thus resulting in a significant increase in citrus yield. (4) Spraying Ca(NO3) on 30 DAFB mainly affected the metabolism of titratable acid (TA) to improve the maturity of citrus fruits. Whilst it improved the external quality and the coloring of citrus fruit significantly. Therefore, Ca(NO3)2 canopy spraying during physiological fruit drop period has a better influence on the tree character and fruit quality of Newhall navel orange (Citrus sinensis Osbeck).

In this study, the removal of bitterness in Washington (navel) orange juice due to limonin was examined by using “Amberlite XAD-7HP” adsorbent. In the meanwhile, the changes on some chemical properties of orange juices such as (pH, titratable acidity, brix) were investigated. It had been determined that the adsorbent was successfully removed the bitterness in Washington navel orange juice. The results showed that bitterness caused from limonin was decreased from 90% to %96 at 30°C and 40°C, respectively. The bitterness of orange juice caused due to limonin was decreased up to %96 during using Amberlite XAD-7HP polymeric resin.

The present study was carried out to improve fruit set, yield, quality, marketability, and exportability of ‘Washington’ Navel orange. Pre-harvest foliar sprays of GA3, K, and Ca, either alone or combined, were applied at full bloom. The following treatments were applied: {control (T1), 25 mg/L GA3 (T2), 2% K2SO4 (T3), 25 mg/L GA3 + 2% K2SO4 (T4), 25 mg/L GA3 + 2% Ca Cl2 (T5), 2% K2SO4 + 2% Ca Cl2 (T6), and 25 mg/L GA3 + 2% K2SO4 + 2% Ca Cl2 (T7). All treatments improved fruit set, yield, physical and chemical characteristics, mineral content of leaves and fruit rind, and the percentage of exportable fruit in comparison to the control. Fruit set, fruit detachment force, peel firmness, and the mineral content of leaves and fruit rind were enhanced significantly with the combination of GA3 + K2SO4 + Ca Cl2 (T7) in comparison to all other treatments and the control. Results indicated that all foliar combination treatments improved fruit quality and marketability, and increased the percentage of expor...

The aroma fraction of fresh fruits is a key factor to evaluate quality and acceptance or resistance of customers. Due to the limited sensitivity of current analytical methods, many important aroma components are unidentified in most studies of fresh fruit. In this work, the aroma compounds in the fresh navel orange were studied by multidimensional gas chromatography quadrupole time-of-flight mass spectrometry which can simultaneously achieve one-dimensional and comprehensive two-dimensional separation on only one instrument, with no need to change columns. As a result, a total of 97 volatile compounds were determined by comprehensive two-dimensional gas chromatography while only 44 compounds were identified by one-dimensional gas chromatography. The identified compounds, which account for 98.30% of the volatile chemicals present in the orange, include 10 aldehydes, 8 ketones, 22 alcohols, 12 esters, 11 hydrocarbons and 34 terpenes. D-limonene was shown to be the predominant compound in fresh navel oranges. The results show that comprehensive two-dimensional gas chromatography provided reliable and comprehensive information on the aroma compounds in fresh navel oranges.

In citrus, post-harvest treatment with ethylene or ethephon in an airtight container frequently resulted in fruit calyx drying, browning and abscission, with a consequent reduction in commercial value. To avoid these problems, pre-harvest degreening with ethepnon was performed on ‘CARA CARA’ navel orange fruits. An earlier and deeper orange colour development was obtained after treatment, reflecting at higher lightness (L*) and a*/b* ratio. The total carotenoid content in flavedo significantly increased, paralleling with a remarkable decrease in chlorophyll content, while in flesh TSS, TA and Vc were all not affected. A transcriptome analysis revealed that 171 genes in flavedo were involved in ethylene-degreening. These ethylene-responsive genes were involved in photosynthesis, chloroplast biogenesis, sugar metabolism, secondary metabolism, and activation of regulatory processes, including transcription regulation and protein posttranslational modification. In the chlorophyll metabolism, a chlorophyllase gene was strikingly increased, indicating the role of ethylene in promoting chlorophyll degradation. While, the genes related to carotenoid metabolism did not show any significant expression change after ethephon treatments. In conclusion, our data showed that pre-harvest degreening was an effective method to accelerate colour improvement, and meanwhile created a solid foundation for future investigations on the molecular mechanism underlying degreening of orange fruits.

Citrus greening disease [Huanglongbing (HLB)] is the most destructive disease of citrus. In this work, we have established a metabolite-based mass spectrometry (MS) method for rapid detection of HLB in navel orange trees. Without sample pretreatment, characteristic mass spectra can be directly obtained from the raw plant samples using the direct MS method. The whole detection process can be accomplished within 1 min. By monitoring and comparisons of the healthy and infected plants throughout a whole year, characteristic MS peaks of metabolites are found to be specific responses from infected plants and, thus, could be used as biomarkers for detection of HLB. Therefore, HLB could be directly detected in the asymptomatic samples, such as stems, using this metabolite-based direct MS method. In addition, principal component analysis and partial least squares discriminant analysis modes of metabolites from healthy and infected trees were established for investigating differentiation and seasonal variations of HLB in leaves, veins, and stems, providing valuable information for understanding the HLB in different seasons.

Zinc (Zn) deficiency is widespread among citrus plants, but information about the mechanisms for Zn deficiency response in these plants is scarce. In the present study, different navel orange ( Citrus sinensis (L.) Osbeck) leaves with various yellowing levels were sampled in our experimental orchard, and upon estimation of nutrient contents, Zn deficiencies were diagnosed as mild, moderate, and severe. Further analysis of chlorophyll content, photosynthetic characteristics, antioxidant enzyme activities, and expression levels of Zn/Iron-regulated transporter-like protein (ZIP) family genes were conducted in the sampled Zn-deficient leaves. The results showed that chlorophyll contents and net photosynthetic rate (P n ) seemed to decrease with reduced Zn contents. In addition, comparison of severe Zn-deficient and normal leaves revealed that activities of peroxidase (POD) and catalase (CAT) increased significantly, whereas that of Zn-containing enzymes such as Cu/Zn superoxide dismutase (Cu/Zn-SOD) significantly reduced with decreasing Zn contents. As expected, expression of the ZIP family genes, ZIP1, ZIP3 , and ZIP4 , was induced by Zn deficiencies. These results deepen our understanding of Zn deficiency in citrus plants as well as provide useful preliminary information for further research.

Inarching is often used to correct nutrient deficiency, but the characteristic of boron (B) uptake in inarched citrus remains unknown. One-year-old ‘Newhall’ navel orange plants on trifoliate orange were inarched with Carrizo citrange seedlings. After a 15-month B deficiency, the plants were resupplied with low B for 35 days to investigate the B uptake and the contribution of inarching rootstock to B absorption in different parts by using 10B labeling and split-root methods. When resupplying low B to B-deficient plants, the B concentration and proportion of newly absorbed B in new leaves, new twigs, and old leaves were higher in inarched than non-inarched plants. By contrast, the B concentration in original rootstock roots of inarched plants was lower than that of non-inarched plants. Regardless of B treatment, the fresh weight in original rootstock roots was significantly lower in inarched than non-inarched plants. Interestingly, the enriched 10B abundance was detected in the original rootstock from split-root treatments in which only the inarching rootstock was supplied with labeled 10B, implying that newly acquired B can be retranslocated from scion to rootstock. The newly-absorbed-B contribution of inarching rootstock was higher for the scion but lower for both rootstocks under low B conditions when compared with B-adequate conditions. These results suggest that, under low B conditions, inarching B-efficient Carrizo citrange onto B-deficient navel orange improves the plant's B uptake, increases the B concentration in young scion parts, and thus enhances the tolerance of the whole plant to B deficiency.

This study investigated the changes in volatile organic compounds (VOCs) of navel orange during fruit maturation. The volatiles in navel orange from July (young fruit period) to November (commercial maturation period) were separated by headspace solid-phase microextraction (HS-SPME) and analyzed using gas chromatography-mass spectrometry (GC-MS). Fifty-seven VOCs were identified and classified into five groups. Through principal component analysis, the samples of different months were discriminated, and one-way analysis of variance showed that 55 volatiles significantly differed during growth. Among the VOCs, the relative concentration of monoterpenes increased with maturity, and D-limonene was the component with the highest content. Similar behavior was exhibited for aldehydes, reaching the maximum content in November. On the contrary, esters decreased its concentration from July to November. The concentration of sesquiterpenes gradually increased, reaching the maximum level between August and November. Moreover, alcohols reached theirs largest content in September, β-Linalool had the highest content among the alcohols. These results provided important theoretical support for the development of navel orange components and comprehensively elucidate the flavor characteristics during the ripening of navel orange.

To clarify whether the rootstock can affect the uptake dynamics of mineral nutrient in the fruit of navel orange, changes in the concentration and quantities of macronutrients (N, P, K, Mg, and Ca) and micronutrients (B, Fe, Mn, Cu, and Zn) in the fruit of Newhall navel orange grafted on trifoliate orange and citrange were measured at semi-monthly intervals during fruit development. The macronutrients measured in this study, except Ca, decreased in concentration on a whole fruit basis during stage I and then remained constant or decreased very slightly during stages II and III of fruit development. Calcium concentration in whole fruit increased during stage I. The elements Mn, Cu and Zn declined in concentration on a whole fruit basis at two rates, very sharply during early stage I and then gradually in the following days to maturity. An exception to this general pattern was boron, where the concentration remained constant during stage I and early stage II and then decreased slightly. For the element Fe, the concentrations showed a large increase and then declined immediately from 120 to 150 days after full bloom (DAFB). With few exceptions (e.g., Fe, Mn, and Zn), the quantity of each element accumulated increased steadily throughout the growth period to reach a maximum by harvest in both grafted plants. Fe accumulation in whole fruit increased from a minimum just after fruit set to a maximum by 135 DAFB. For a number of elements (N, P, K, B, and Mn), there was a strong linear correlation (R2 > 0.95, P

Navel orange is a very popular fruit which is rich in nutrition necessary to human health. Nowadays, rapid, nondestructive and pollution-free analysis of internal organic compounds of fruit is an important and promising technology. The purpose of this paper is to present a swarm intelligence optimization method to extract the feature information of visible-near infrared (Vis-NIR) spectra of navel orange for rapid and nondestructive analysis of soluble solid content (SSC) in navel orange. This method was developed on particle swarm optimization (PSO) and named as piecewise particle swarm optimization (PPSO). The experimental results showed that the PPSO algorithm proposed in this paper overcame the disadvantage of PSO's premature convergence. The PLS model based on variables selected by PPSO for nondestructively detecting SSC of navel orange yield promising results, as the standard deviation of prediction (SEP) was 0.427°Brix while the standard error of laboratory (SEL) was 0.22°Brix. It indicated that the application of near infrared spectroscopy (NIRS) technology combined with PPSO for rapid analysis of soluble solid content in navel orange was feasible.

Delayed bitterness causes severe economic loss in citrus juice industry worldwide, which is mostly due to the formation of limonoid compounds, especially limonin, in juice. In this study, effects of postharvest time of fruits, heat treatment, pH and filtration of juice on limonin content in Newhall navel orange (Citrus sinensis Osbeck cv. Newhall) juice were investigated. Our research indicated for the first time that: (1) limonin content in juice would gradually increase to a maximal level and then remained almost constant thereafter as storage time going on, whereas the maximum constant value (MCV) of limonin content in juice significantly (p &lt, 0.05) decreased with the increment of postharvest time of fruits being juiced, (2) heat treatment and acidification of juice only speeded up the formation of limonin to the maximal level while without changing the MCV of limonin content, (3) the juice after filtration exhibited much lower MCV of limonin content compared with the unfiltered one. These experimental observations might not only provide useful information for the development of new debitterness method for navel orange juice, but also strongly support the acid-promoted delayed bitterness mechanism, suggesting the formation of delayed bitterness might primary due to the acid-promoted rather than the enzyme-catalyzed lactonization of limonoate A-ring lactone (LARL) to produce limonin in juice of navel orange.

The aim of this study was to investigate the efficacy of navel orange, Citrus sinensis (L.) Osbeck, peel essential oil (NOPEO) for inhibiting spoilage fungi in potato slices. Sixteen different components accounting for 99.79% of the headspace components of NOPEO were identified by gas chromatography-mass spectrometry. d-Limonene was the major component of NOPEO. Antifungal activity of NOPEO was tested in vitro and in vivo against four foodborne fungi. A MIC of NOPEO against the four fungal species was 9.40 μL/mLair. NOPEO provided about 74, 74, 73, and 69% protection against Aspergillus niger, Mucor wutungkiao, Penicillium funiculosum, and Rhizopus oryzae at 2.00 μL/mLair concentration, respectively. NOPEO has been demonstrated to significantly improve the microbiological quality of potato slices.

The flavor quality of citrus fruits is largely determined by the sugar-acid ratio, but it remains uncertain how sugar- and/or acid-metabolizing enzymes regulate the sugar-acid ratio of navel oranges and further affect the fruit quality. In the present study, Robertson navel oranges (Citrus sinesis Osb.) were collected from six representative habitats in three eco-regions of Sichuan, China. The changes in the sugar-acid ratio and the activities of sucrose phosphate synthase (SPS), sucrose synthase (SS), cytosolic cio-aconitase (ACO), and isocitrate dehydrogenase (IDH) were examined in navel oranges during fruit development. The results indicated that the sugar-acid ratio of fruits in different eco-regions changed significantly from 150 days after full bloom. The SPS and cytosolic ACO fruit activities had minor changes among different ecoregions throughout the experimental periods, whereas the activities of SS and IDH changed significantly in fruits among three eco-regions. Furthermore, the sugar-acid ratio and the activities of SS in the synthetic direction and IDH were the highest in south subtropics and the lowest in north mid-subtropics, probably due to the effects of climate conditions and/or other relevant eco-factors. It demonstrated that SS in the synthetic direction and IDH were of greater importance in regulating the sugar-acid ratio of navel oranges in different eco-regions, which provided new insights into the factors that determine the flavor quality of navel oranges and valuable data for guiding relevant agricultural practices. RESUMO A qualidade do sabor das frutas cítricas é amplamente determinada pela relação açúcar- ácido, mas permanece incerto como enzimas metabolizadoras de açúcar e / ou do ácido regulam a relação açúcarácido de laranjas de umbigo e depois afetarem a qualidade dos frutos. No presente estudo, laranjas de umbigo Robertson (Citrus sinensis Osb.) foram coletadas de seis habitats representativos em três ecorregiões do Sichuan, na China. As mudanças na relação açúcar-ácido e as atividades da síntese de sacarose fosfato (SPS), síntese de sacarose (SS), aconitase citossólica (ACO) e isocitrato desidrogenase (IDH) foram examinadas em laranjas de umbigo durante o desenvolvimento dos frutos. Os resultados indicaram que a relação açúcar-ácido de frutas em diferentes ecorregiões alterou significativamente a partir de 150 dias após a plena floração. O SPS e as atividades ACO citossólicas das frutas tiveram pequenas alterações entrediferentes ecorregiões ao longo dos períodos experimentais, enquanto que as atividades da SS e IDH alteraram significativamente em frutas entre três ecorregiões. Além disso, a relação açúcar-ácido e as atividades da SS na direção sintética e IDH foram as mais elevadas em regiões subtropicais sul e as mais baixas nas regiões do meio-subtropical norte, provavelmente devido aos efeitos das condições climáticas e / ou outros fatores-ecológicos. Demonstrou-se que a SS na direção sintética e IDH foram de maior importância na regulação da relação açúcar-ácido de laranjas de umbigo em diferentes ecorregiões, que forneceu novas descobertas sobre os fatores que determinam a qualidade do sabor das laranjas de umbigo e dados valiosos para orientar práticas agrícolas relevantes.

Oranges (Citrus sinensis) can provoke an allergic reaction in some individuals. The concentration of profilin (Cit s 2) – the major allergen in oranges – is unknown, but this knowledge could be useful for preventing the development of allergies. The aim of this study was to quantify the amount of Cit s 2 in Navel oranges and in different varieties of citrus fruit. A sandwich enzyme-linked immunosorbent assay (ELISA) was developed using both monoclonal and polyclonal antibodies. Extracts of Navel oranges and 12 citrus fruits were tested using this ELISA. Cit s 2 levels in the Navel orange pulp and peel were 1.81 ± 0.74 and 1.19 ± 0.87 µg/g, respectively, with accumulation detected primarily in the pulp. These findings may help in the production of low-risk processed oranges for orange allergy sufferers through selection of orange varieties and parts with low profilin content during food processing.