Citrus Types Research Articles

Preharvest Mandarin Rind Disorder: Insights into Varietal Differences and Preharvest Treatments Effects on Postharvest Quality.

The citrus industry loses a significant amount of mandarin fruits either before or shortly after harvesting due to rind disorder. Different citrus cultivars are impacted by a physiological rind disorder that lowers fruit quality and marketability. Although the primary etiology of this condition is unknown, changes in relative humidity (RH) and rind water status can make it worse. The damage is initiated in the fall, especially following rain. It begins with irregular water-soaked areas that develop into dark-brown, necrotic lesions covering large portions of the fruit's surface. The damage is evident in some citrus types such as Satsuma Owari mandarins and other cultivars. In this study, we attempted to understand and control the occurrence of this kind of rind disorder in Satsuma Owari mandarins growing under California conditions. Our data showed that fruit located in the outer part of the canopy suffer more than fruit in the interior canopy. We were able to reduce this damage in Satsuma Owari mandarins by applying 2,4-dichlorophenoxyacetic acid (2,4-D) at 16 milligrams/Liter (mg/L), gibberellic acid (GA3) at 20 mg/L, or Vapor Gard® at 0.5 percent (v/v) at the color break stage. However, GA3 caused a delay in color development by approximately four weeks. GA3-treated fruit changed their color completely four weeks after the control, and the rind damage was at a very low percentage. Delaying rind senescence could be a good strategy to reduce the damage in mandarin orchards. Data showed that in addition to the benefits of the different treatments on preventing rind disorder at harvest, they have some beneficial effects during storage for four weeks either at 0.5 or 7.5 °C.

A meta-analysis investigating the influence of citrus by-product pretreatment on lipid oxidation levels in stored chicken meat

This study extensively investigates the impact of citrus by-products on the oxidative stability of chicken meat. The literature review, spanning from 2000 to 2023, involved a thorough screening process, adhering to stringent selection criteria guided by PRISMA-P guidelines. The utilization of Hedge’s model meta-analysis to examine the distinctions between the control and treatment groups, wherein the random effect accounts for inter-study differences, and the fixed effect pertains to the impact of the addition of citrus by-product to chicken meat. Citrus by-products from various fruits, applied under diverse conditions, consistently and significantly reduced TBARS levels throughout the storage period, resulting in an overall mean effect size of -2.57 (P<0.001). While most citrus types displayed a non-significant trend with prolonged storage, both seed and peel components exhibited a significant reduction in TBARS levels (P<0.05). Notably, citrus by-products, especially in whole chicken meat and through marination pretreatment, demonstrated substantial reductions in TBARS values (P<0.01). This metaanalysis underscores the potential of citrus by-product to effectively enhance the oxidative stability of chicken meat during storage, providing valuable insights for further research and practical applications in food preservation.

Cytochrome P450 CitCYP97B modulates carotenoid accumulation diversity by hydroxylating β-cryptoxanthin in Citrus

Carotenoids in plant foods provide health benefits by functioning as provitamin A. One of the vital provitamin A carotenoids, β-cryptoxanthin, is typically plentiful in citrus fruit. However, little is known about the genetic basis of β-cryptoxanthin accumulation in citrus. Here, we performed a widely targeted metabolomic analysis of 65 major carotenoids and carotenoid derivatives to characterize carotenoid accumulation in Citrus and determine the taxonomic profile of β-cryptoxanthin. We used data from 81 newly sequenced representative accessions and 69 previously sequenced Citrus cultivars to reveal the genetic basis of β-cryptoxanthin accumulation through a genome-wide association study. We identified a causal gene, CitCYP97B, which encodes a cytochrome P450 protein whose substrate and metabolic pathways in land plants were undetermined. We subsequently demonstrated that CitCYP97B functions as a novel monooxygenase that specifically hydroxylates the β-ring of β-cryptoxanthin in a heterologous expression system. In planta experiments provided further evidence that CitCYP97B negatively regulates β-cryptoxanthin content. Using the sequenced Citrus accessions, we found that two critical structural cis-element variations contribute to increased expression of CitCYP97B, thereby altering β-cryptoxanthin accumulation in fruit. Hybridization/introgression appear to have contributed to the prevalence of two cis-element variations in different Citrus types during citrus evolution. Overall, these findings extend our understanding of the regulation and diversity of carotenoid metabolism in fruit crops and provide a genetic target for production of β-cryptoxanthin-biofortified products.

YOLOC-tiny: a generalized lightweight real-time detection model for multiripeness fruits of large non-green-ripe citrus in unstructured environments.

This study addresses the challenges of low detection precision and limited generalization across various ripeness levels and varieties for large non-green-ripe citrus fruits in complex scenarios. We present a high-precision and lightweight model, YOLOC-tiny, built upon YOLOv7, which utilizes EfficientNet-B0 as the feature extraction backbone network. To augment sensing capabilities and improve detection accuracy, we embed a spatial and channel composite attention mechanism, the convolutional block attention module (CBAM), into the head's efficient aggregation network. Additionally, we introduce an adaptive and complete intersection over union regression loss function, designed by integrating the phenotypic features of large non-green-ripe citrus, to mitigate the impact of data noise and efficiently calculate detection loss. Finally, a layer-based adaptive magnitude pruning strategy is employed to further eliminate redundant connections and parameters in the model. Targeting three types of citrus widely planted in Sichuan Province-navel orange, Ehime Jelly orange, and Harumi tangerine-YOLOC-tiny achieves an impressive mean average precision (mAP) of 83.0%, surpassing most other state-of-the-art (SOTA) detectors in the same class. Compared with YOLOv7 and YOLOv8x, its mAP improved by 1.7% and 1.9%, respectively, with a parameter count of only 4.2M. In picking robot deployment applications, YOLOC-tiny attains an accuracy of 92.8% at a rate of 59 frames per second. This study provides a theoretical foundation and technical reference for upgrading and optimizing low-computing-power ground-based robots, such as those used for fruit picking and orchard inspection.

Comparison of leaf chlorophyll content retrieval performance of citrus using FOD and CWT methods with field-based full-spectrum hyperspectral reflectance data

Citrus is one of the most economically valuable fruit trees in the world, for which leaf chlorophyll content (LCC) serves as a crucial indicator for evaluating its growth and health status. However, the quantitative estimation of LCC using remote-sensing techniques is still challenging owing to unclear sensitive spectral ranges, baseline drift and overlapping spectrum peaks. To resolve these issues, we clarified the spectral response characteristics of citrus LCC using fractional-order derivatives (FOD) and continuous wavelet transform (CWT) methods to determine its sensitive spectral range with in situ full-spectrum leaf hyperspectral data. We proposed a novel method for estimating the LCC of citrus by combining an ensemble learning regression model based on Hyperopt optimization (H-ELR) with partial least squares regression (PLSR) using the ultra-high dimensional feature variables produced by dual- and tri-band combination strategies. We evaluated the retrieval performance of LCC between the FOD- and CWT-based optimal spectral feature variables. Besides, we further examined the feasibility of improving the estimation accuracy of LCC by the combination of their optimal feature variables. Finally, we evaluated the effect of the spectral curve trend changes and different dimensional spectral features on LCC estimation. The results showed that: (1) The FOD- and CWT-based methods improved the correlation between original spectral reflectance and LCC, with the correlation coefficient increasing by 0.046 and 0.054, respectively. We confirmed that 425–740 nm is the optimal spectral range for LCC estimation. (2) We found that the 0.9 order derivative Tri-band index (TBI2 (R571, R1697, R740)) constructed by combining the sensitive spectral bands of leaf water content achieved a high-precision LCC estimation (R2 = 0.876). In addition, the MERIS terrestrial chlorophyll index (MTCI) constructed based on the scale6 of CWT also gained good retrieval accuracy (R2 = 0.806). (3) We demonstrated that a combination of FOD-based and CWT-based sensitive spectral features improves estimation accuracies (R2 = 0.891) of LCC and revealed that the reflectance peaks and slope peaks at 550 and 750 nm are essential variables for predicting the citrus LCC. (4) The combination of PLSR and H-ELR model provided a good retrieval performance of citrus LCC with the kurtosis (γ = 3.2) and skewness (Sk = 0.066) of the residual prediction values. Our proposed method can provide a scientific basis for estimating LCC and other physiological parameters of citrus and other crop types, which is also important to optimize agricultural management practices and improve crop yield.

Effect of Irrigation with Saline Water on the Growth of three types of Citrus Grafted on the Sour Orange Rootstock

Effect of Irrigation with Saline Water on the Growth of three types of Citrus Grafted on the Sour Orange Rootstock

Sonication results in variable quality and enhanced sensory attributes of Adajamir (Citrus assamensis) juice: A study on an underutilized fruit

Citrus assamensis, commonly known as Adajamir, is an underutilized fruit with distinctive sensory and nutritional properties. The limited amount of research on this particular citrus type was recognized as one of the research gaps for this study. The objective of this study was to evaluate and compare the impacts of sonication, pasteurization, and thermosonication techniques on the quality and sensory attributes of Adajamir juice. A randomized experimental design was used in the study, wherein the juice underwent three different treatments. The results indicate that there were no significant changes in pH or titratable acidity following all treatments. Yet, notable differences in juice color were observed. The use of sonication and thermosonication resulted in an increase in β-carotenoid levels. Additionally, total phenolic content and antioxidant activities were observed to increase. All three treatments led to a reduction in ascorbic acid levels relative to the control. However, the complete elimination of microbial growth was observed during the thermal treatment. Compared to other approaches, sonication has been shown to be notably more efficacious in enhancing both the flavor and aroma. Sonication has been observed to improve the perceived bitterness to a certain degree. These findings support the potential of sonication as an alternative preservation method for Adajamir juice, offering enhanced quality and sensory acceptance.

GRAPEVINE VEIN-CLEARING VIRUS IS MEALYBUG-BORNE BUT NOT MEALYBUG-TRANSMITTED

This article investigates the ability of two types of mealybugs, citrus (Planococcus citri) and longtailed (Pseudococcus longispinus) mealybugs, of acquiring and transmitting Grapevine vein-clearing virus (GVCV) in a greenhouse setting. Mealybugs are the primary vectors for most Badnaviruses, and only a few species have been shown to be aphid-transmitted. In this study, we tested the acquisition and transmission ability of two mealybug species using GVCV-infected and healthy grapevines in a greenhouse setting for three consecutive seasons. This study determined that acquisition time by the mealybugs could be as low as three days, yet the transmission of GVCV from infected grapevines to healthy grapevines by these two mealybug species was unsuccessful. Additionally, with the use of previously-developed species-specific primers, this study determined that those mealybugs captured in the greenhouse facilities at the University of Missouri could not be identified using these primers, and required primers that were specific to their regional diversity. This study contributes to the wider understanding of the acquisition and transmission of GVCV by certain mealybug species.

Effect of plant growth regulators on postharvest calyx retention of citrus fruit

Abscission is a naturally occurring physiological process that enables plant organ separation in response to various developmental, hormonal and/or environmental signals. Postharvest calyx abscission can adversely affect fruit quality and diminish the cosmetic appearance. Synthetic auxins are applied to impede abscission, of which 2,4-dichlorophenoxy acetic acid (2,4-D) is the most widely used in citriculture. However, due to restrictions imposed on the use of 2,4-D, it is imperative to investigate potential alternatives with relatively lower toxicities and similar performance concerning citrus postharvest quality maintenance. This study aimed to evaluate the relative efficacy of five plant growth regulators [amimoethoxyvinyl-glycine (AVG), 3,5,6-trichloro-2-pyridyloxyacetic acid (3,5,6-TPA), 2-(4-amino-3,5-dichloro-6-fluoropyridin-2yl) oxyacetic acid (Fluroxypyr), s-ethyl-4-chloro-O-tolilooxytioacetate (MCPA) and gibberellic acid (GA3)] to minimise postharvest calyx senescence and abscission, with Ethephon as the negative control. All of the auxin treatments positively affected the calyx condition when compared to the control fruit. This study showed potential alternatives for 2,4-D that elicit the same effect on quality parameters, however, citrus type and cultivar influenced susceptibility to calyx senescence and response to plant growth regulators. 3,5,6-TPA showed similar effects to 2,4-D in maintaining calyx condition and overall fruit quality for ‘Nules Clementine’ mandarin. AVG and Fluroxypyr showed comparable effects to 2,4-D in minimising calyx senescence while upholding the commercial quality of other parameters for ‘Esbal Clementine’ mandarin and ‘Washington’ navel orange. MCPA maintained external and internal quality parameters equivalent to 2,4-D in ‘Eureka’ lemon. Ethephon’s effect on calyx condition generated a new theory where ethylene and programmed cell death might be involved in an alternative, generalised senescence route, resulting in calyx fusion.

The Effectiveness of Edible Coating Aloe Vera (Aloe vera chinensis L.) in Inhibiting Enzymatic Browning on Sliced Apples

Apple is a fruit that turn brown quickly after being cut. One method to maintain the quality of apples cut is coating the fresh-cut apples with an edible coating. Ediblei coatingi is a thini ilayer that can bei eaten and can keep the iquality ofi the icoated material. Thei study aimed toi determinei the effectiveness of edible coating aloe vera (Aloe vera chinensis L.) in inhibit enzymatic browning reaction. The designii wasi usiing icompletely irandomized idesign. The first factor was the citrus species (Citrus aurantifolia, Citrus hystrix DC, Citrus amblycarpa) iand the secondi factori was thei istorage itime (0, 3, 6 day). Edible coating applied to fresh-cut apples and tested for moisture content, total dissolved solids, weight loss, color, overall appearance, vitamin C and total plate count. Thei resultsi ishowed that aloe vera edible coating with citrus extract was not effective in inhibiting the enzymatic reaction of sliced apples. The type of citrus and storage time was affect the effectiveness of aloe vera edible coating. Citrus amblycarpa extract has a lower water content reduction effect with a water content of 54.51% on the 6th day of storage time and has an effect on the total plate count, that Citrus amblycarpa extract has decreased total plate count in day 6th. Citrus aurantifolia extract gives the effect of maintaining brightness compared to other types of citrus, with a brightness value of 58,290 on the 6th day. The type of citrus has no effect on weight loss, total dissolved solids, overall appearance. The length of storage has an effect on the effectiveness of aloe vera edible coating, the longer it is stored, the apples cut will decrease in quality.

Oviposition by the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), on five citrus types in a laboratory

AbstractFrugivorous insects use visual, chemical and tactile cues to find a suitable host for oviposition. However, these cues can vary greatly among fruit cultivars and condition, changing their susceptibility to fruit fly oviposition. The aims of this study were to (1) determine the effects of ripeness stage and damage on oviposition propensity by sexually mature, mated female oriental fruit flies, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), on five citrus types (species and cultivars) under choice and no‐choice conditions and (2) describe the oviposition behaviour of B. dorsalis on ripe fruit of the same five citrus types that were either damaged or undamaged under no‐choice conditions. All tests were conducted in the laboratory. The citrus types tested were Citrus sinensis (L.) Osbeck cv Delta Valencia orange, Citrus sinensis (L.) Osbeck cv Glen Ora Late navel orange, Citrus limon (L) (Burm.f.) cv Eureka lemon, Citrus paradisi (Macfad.) cv Star Ruby grapefruit and Citrus reticulata (Blanco) cv Nadorcott mandarin. Peel physical properties and essential oil composition were determined for each citrus type and stage. Oviposition propensity of B. dorsalis was significantly greater on damaged citrus but was not correlated with fruit diameter, peel thickness, oil gland density or oil gland size. A total of 45 aromatic compounds were found to be significant between the five cultivars investigated, and 6 of 11 compounds were significantly associated with over‐ripe fruits. Bactrocera dorsalis spent a significantly greater proportion of time ovipositing in damaged citrus and showed higher aggression when oviposition occurred in undamaged citrus. These results suggest that the removal of damaged and fallen fruit is important for controlling this pest in citrus orchards.

Molecular physiology for the increase of soluble sugar accumulation in citrus fruits under drought stress

To investigate the mechanism for drought promoting soluble sugar accumulation will be conducive to the enhancement of citrus fruit quality as well as stress tolerance. Fruit sucrose mainly derives from source leaves. Its accumulation in citrus fruit cell vacuole involves in two processes of unloading in the fruit segment membrane (SM) and translocating to the vacuole of fruit juice sacs (JS). Here, transcript levels of 47 sugar metabolism- and transport-related genes were compared in fruit SM or JS between drought and control treatments. Results indicated that transcript levels of cell wall invertase genes (CwINV2/6) and sucrose synthase genes (SUS2/6) in the SM were significantly increased by the drought. Moreover, transcript levels of SWEET genes (CsSWEET1/2/4/5/9) and monosaccharide transporter gene (CsPMT3) were significantly increased in SM under drought treatment. On the other hand, SUS1/3 and vacuolar invertase (VINV) transcript levels were significantly increased in JS by drought; CsPMT4, sucrose transporter gene 2 (CsSUT2), tonoplast monosaccharide transporter gene 2 (CsTMT2), sugar transport protein gene 1 (CsSTP1), two citrus type I V-PPase genes (CsVPP1, and CsVPP2) were also significantly increased in drought treated JS. Collectively, the imposition of drought stress resulted in more soluble sugar accumulation through enhancing sucrose download by enhancing sink strength- and transport ability-related genes, such as CwINV2/6, SUS2/6, CsSWEET1/2/4/5/9, and CsPMT3, in fruit SM, and soluble sugar storage ability by increasing transcript levels of genes, such as CsPMT4, VINV, CsSUT2, CsTMT2, CsSTP1, CsVPP1, and CsVPP2, in fruit JS.

Early-Season forecasting of citrus block-yield using time series remote sensing and machine learning: A case study in Australian orchards

This study presents a comprehensive evaluation of seasonal, locational, and varietal variations in canopy reflectance responses in 315 commercial citrus blocks from three major growing regions in Australia. The dataset includes three different citrus types (Mandarin, Navel, Valencia) and 26 varieties. The aim is to utilize this combined information to better understand yield variation and develop improved forecasting models. Landsat satellite data spanning from October 2006 to February 2021 (1419 tiles) were used to derive reflectance values, and calculate four vegetation indices (NDVI, GNDVI, LSWI, and GCVI), for each citrus block. These indices were then analyzed alongside corresponding yield data, which consisted of 3660 individual yield records dating back to 2007. Two temporal resolutions were incorporated as predictors: spatio-temporal vegetation index time series (TS) aggregated every two months and annual time series of historical block-yield records. Six statistical and machine learning algorithms were calibrated using a leave-one-year-out cross-validation approach (LOYO CV) and validated for one-year forward prediction over a five-year period (2017–2021). The results highlight significant yield variations across years, alternate bearing patterns, and spatio-temporal changes in reflectance profiles influenced by seasonal conditions, varietal characteristics, and locations. The support vector machine (SVM) algorithm with a radial basis function kernel consistently outperformed other algorithms, indicating a non-linear relationship between citrus yield and predictors. The SVM model achieved an RMSE of 15.5 T ha−1, R2 of 0.88, MAE of 12.1 T ha−1, and MAPE of 29% in predicting block-yield across farms, varieties, and seasons. These prediction accuracy metrics demonstrate an improvement over current forecasting methods. Notably, the proposed approach utilizes freely available imagery, provides forecasts between two to nine months before harvest, and eliminates the need for infield counting of fruit load for image calibration. This approach provides an improved method for understanding seasonal yield variation and quantifying citrus block-yield, offering valuable insights for growers in harvest logistics, labor allocation, and resource management.

Seasonal Distribution and Food Preference of the Peach Fly, Bactrocera zonata (Saunders) on Different Types of Citrus Fruit Trees in Baghdad Governorate

Al-Jassani, R.F. and A.H. Abou Rgheef. 2023. Seasonal Distribution and Food Preference of the Peach Fly, Bactrocera zonata (Saunders) on Different Types of Citrus Fruit Trees in Baghdad Governorate. Arab Journal of Plant Protection, 41(2): 93-97. https://doi.org/10.22268/AJPP-41.2.093097 The study was conducted in an orchard in Baghdad city to monitor infestation rate and movement of Bactrocera zonata in infested fruits during different periods. Results obtained showed that the seasonal distribution of the peach fruit fly B. zonata was proportional to the presence of the fruits and their maturity stage in the orchard. Apricots infestation occurred in May and June, peach in June and July, yellow figs in July and August, mango in August and September, mandarin in October and November, oranges in November and December, and sour orange in December. The results of the study demonstrated that the peach fruit fly varied in its preference and infestation of the different citrus species fruits, based on fruits infestation rates and the average larvae number per fruit. Mandarin fruits were the most preferred types of citrus by B. zonata, followed by orange fruits, grapefruit, sindhi, sweet lemon, and sour orange. In contrast, the sour lemon fruits were not infested. The seasonal distribution of fruit types is important and can be used in the design of preventive control strategies to protect the various fruits from insect’s infestation. Keywords: Peach fruit fly, seasonal distribution, Baghdad, mandarin, sour orange

Longevidade pós-colheita de tangerina Fremont IAC 543

Abstract The planting of new types of table citrus is an interesting alternative for citrus growers in the state of Paraná, as this domestic market continues to grow and needs innovation. Thus, the aim of this study was to evaluate the acceptance and storage of a new hybrid for the region of Londrina / PR, Fremont IAC 543 mandarin (Citrus clementina hort. ex Tan x C. reticulataBlanco). Treatments were: storage of fruits with and without wax coating at room temperature [21 ± 2 °C and relative humidity (RH) = 60 ± 5%] for up to 36 days. Sensory (acceptance test and purchase intention) and physicochemical analyses [weight, juice yield, acidity, soluble solids and soluble solids/titratable acidity (ratio)] were performed before and after storage. Physicochemical data were submitted to analysis of variance and regression, while sensory analysis results were explored through descriptive statistics and principal components analysis using the R statistical software. It could be concluded that Fremont IAC 543 mandarin can be stored with wax coating and at room temperature without losing its quality characteristics for a period of up to 18 days.

Pengaruh Metode Sterilisasi Permukaan terhadap Kultur Biji Jeruk Japansche Citroen (JC) Citrus limonia Osbeck

Effect of Surface Sterilization Methods on Seed Culture of JC Citrus limonia Osbeck Japansche Citroen (JC) Citrus limonia Osbeck is one type of citrus that is commonly used as rootstock. JC seed propagation through in vitro culture will be more effective. The initiation stage is the first step of in vitro culture to obtain microbial-free explants and initiate the initial growth. At this stage the problem of contamination becomes the main limiting factor. This study aims to obtain the appropriate method of sterilizing of JC orange seed explants in in vitro culture propagation. A total of four sterilization methods have been tested at the Tissue Culture Laboratory, Department of Biology, Faculty of Mathematics and Natural Sciences, Hasanuddin University. The sterilization material used is tween 80, fungicide, 20-30% NaOCl and 90% alcohol. The variables observed in this study were the time of appearance of contamination, the percentage of types of contaminants (bacteria and fungi), the percentage of sterile explants and the percentage of live explants after 28 days of culture. The results showed that the fourth method was the optimal sterilization method with the lowest contamination level of 30% of the other three methods with the highest explant survival rate of 60% compared to the other three methods.

The biological effect of orange (Citrus sinensis L.) by-products on metabolic biomarkers: A systematic review

Industrial processing of citrus fruits generates an important amount of wastes that evoke environmental damage. Orange is the main citrus fruit consumed worldwide, and after its use, approximately more than a half of the fruit remains as by-products, which comprise important bioactive compounds useful for the development of promising nutraceuticals for the treatment of non-communicable diseases. This study aimed to gather scientific evidence about the biological effects of orange by-products using a systematic review. A total of 14 studies that were carried out in rodent models in the last 10 years were retrieved from PubMed and ScienceDirect databases. Studies that used another animal species, another type of citrus, or a combination of orange with other citrus were excluded. The risk of bias was assessed by using the SYRCLE RoB tool, and the results obtained are shown in an informative table, which showed that most of the studies used a pathological model of chronic diseases. We found that the peel is the most used agri-food by-product, and that it has the potential of reducing the levels of triglycerides, total cholesterol, glucose, and systolic blood pressure. However, to clinically assess these effects, these results need to be tested in future in humans. The included studies on the use of orange by-products strengthen the global sustainable food agenda. It is important to consider new research directions about the use of citrus fruit residues since it not only impacts the problem of its disposal but also provides solutions to eliminate the resulting contamination.

Ekspresi morfologi tiga jenis jeruk sebagai indikator ketahanan terhadap serangan Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae)

Salah satu hama penting benih tanaman jeruk adalah tungau perak jeruk (TPJ) Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae). Penelitian ini bertujuan untuk mengkaji pengaruh serangan TPJ terhadap morfologi daun dan tingkat ketahanan tiga jenis jeruk. Tiga jenis jeruk, yaitu Siam, Keprok, Manis digunakan sebagai tanaman uji. Tunas dari ketiga jenis jeruk tersebut diuji kandungan nutrisinya dan dilakukan infestasi TPJ sebanyak 5 individu pada tunas yang berumur lebih kurang 10 hari. Pengamatan populasi TPJ dilakukan 7 hari setelah infestasi (HSI) dan pengamatan selanjutnya dilaksanakan 4 hari sekali. Hasil penelitian menunjukkan kelimpahan TPJ paling rendah pada 23 HSI didapat pada jenis Siam (0,5 ± 0,38 individu) dan Keprok (0,25 ± 0,16 individu). Populasi TPJ meningkat pada 11 sampai 15 HSI, dan mulai menurun pada 19 HSI. Berdasarkan analisis korelasi Pearson, kelimpahan TPJ dipengaruhi oleh kadar lemak dan serat kasar daun. Hasil pengamatan juga menunjukkan bahwa jenis Manis lebih tahan dibandingkan dengan jenis lainnya. Dapat disimpulkan, jenis Manis masih lebih tahan dibandingkan dengan jenis Siam dan Keprok.

Postharvest application of imazalil sulphate using a heated flooder for control of citrus green mould

High volume aqueous applications of imazalil (IMZ) are commonly used in major citrus producing industries for control of green mould, caused by Penicillium digitatum. The flooder application is a more novel means of application where the heated fungicide solution is applied in high volume and low pressure through weirs creating a waterfall over a set of rotating brushes. A five-weir flooder is compared to the conventional dip tank application in terms of residue loading, curative and protective control as well as sporulation inhibition. Imazalil sulphate was applied with a flooder (250 mg L-1 at pH ≈ 5 for 8 s) or a dip tank (500 mg L-1 at pH ≈ 3 for 60 s) on various citrus types at solution temperatures of 25, 35 or 52 °C. All treatments deposited IMZ residues in the fruit of ≈ 1.00 mg kg-1, except residues of ≈ 2.00 mg kg-1 after treatment at 52 °C. Flooder application gave similar curative control and better protective control compared to the dip application. Sporulation control by IMZ was significantly improved when applied with the flooder at 52 °C, compared to the dip treatment. Imazalil sulphate application at 250 and 500 mg L-1 was optimised at temperatures from 25° to 60°C. Regression models describing residue loading in a pH 5, 250 mg.L-1 solution applied by flooder at 26.9 or 47.4 °C would deposit residues of 1 and 2 mg.kg-1, respectively. Regression models describing residue loading in a pH 3, 500 mg.L-1 solution applied by flooder at 38.0 or 63.20 °C would deposit residues of 1 and 2 mg.kg-1, respectively. Curative and protective control was generally good (> 80%), but consistently better after treatment with 500 mg L-1. The influence of number of flooder weirs (1−5) and IMZ solution temperature range of 25–55 °C was determined. A single weir loaded an imazalil residue between 1.00 and 1.50 mg kg-1 regardless of solution temperature. Residue loading was markedly increased at 45 °C with three weirs and 2 mg kg-1 was only exceeded at 55 °C with 3–5 weirs. Curative green mould control (≈90%) and sporulation inhibition (>50%) were more consistent and better when imazalil was applied at 45 °C or higher using three or more weirs. The heated flooder application is an effective alternative to the fungicide dip tank.

Combined Transcriptome and Metabolome Analyses Reveal Candidate Genes Involved in Tangor (Citrus reticulata × Citrus sinensis) Fruit Development and Quality Formation

Tangor, an important citrus type, is a hybrid of orange and mandarin and possesses their advantageous characteristics. Fruit quality is an important factor limiting the development of the citrus industry and highly depends on fruit development and ripening programs. However, fruit development and quality formation have not been completely explored in mandarin-orange hybrids. We sequenced the metabolome and transcriptome of three mandarin-orange hybrid cultivars at the early fruiting [90 days after full bloom (DAFB)], color change (180 DAFB), and ripening (270 DAFB) stages. Metabolome sequencing was performed to preliminarily identify the accumulation patterns of primary and secondary metabolites related to fruit quality and hormones regulating fruit development. Transcriptome analysis showed that many genes related to primary metabolism, secondary metabolism, cell wall metabolism, phytohormones, and transcriptional regulation were up-regulated in all three cultivars during fruit development and ripening. Additionally, multiple key genes were identified that may play a role in sucrose, citric acid and flavonoid accumulation, cell wall modification, and abscisic acid signaling, which may provide a valuable resource for future research on enhancement of fruit quality of hybrid citrus. Overall, this study provides new insights into the molecular basis of pulp growth and development regulation and fruit quality formation in mandarin-orange hybrids.