Canine olfactory detection of a vectored phytobacterial pathogen, Liberibacter asiaticus, and integration with disease control.

Early detection and rapid response are crucial to avoid severe epidemics of exotic pathogens. However, most detection methods (molecular, serological, chemical) are logistically limited for large-scale survey of outbreaks due to intrinsic sampling issues and laboratory throughput. Evaluation of 10 canines trained for detection of a severe exotic phytobacterial arboreal pathogen, Candidatus Liberibacter asiaticus (CLas), demonstrated 0.9905 accuracy, 0.8579 sensitivity, and 0.9961 specificity. In a longitudinal study, cryptic CLas infections that remained subclinical visually were detected within 2 wk postinfection compared with 1 to 32 mo for qPCR. When allowed to interrogate a diverse range of in vivo pathogens infecting an international citrus pathogen collection, canines only reacted to Liberibacter pathogens of citrus and not to other bacterial, viral, or spiroplasma pathogens. Canines trained to detect CLas-infected citrus also alerted on CLas-infected tobacco and periwinkle, CLas-bearing psyllid insect vectors, and CLas cocultured with other bacteria but at CLas titers below the level of molecular detection. All of these observations suggest that canines can detect CLas directly rather than only host volatiles produced by the infection. Detection in orchards and residential properties was real time, ∼2 s per tree. Spatiotemporal epidemic simulations demonstrated that control of pathogen prevalence was possible and economically sustainable when canine detection was followed by intervention (i.e., culling infected individuals), whereas current methods of molecular (qPCR) and visual detection failed to contribute to the suppression of an exponential trajectory of infection.

First Report of Lasiodiplodia pseudotheobromae causing Postharvest Decay of Strawberries in Florida.

Postharvest decay of strawberry (Fragaria × ananassa Duch.) is a major factor causing fruit losses. Strawberries were obtained from various harvests at cooling facilities located in Dover and Plant City, FL during the 2018-19 and 2019-20 seasons. After the fruits were incubated at 22ºC for up to 5 days (d) to promote disease development, Lasiodiplodia decay was observed at up to 3% from some harvests, exhibiting gray mycelia on small lesions that gradually covered the whole fruit. The fungus was isolated onto potato dextrose agar (PDA). Five isolates (SBD18-14, SBD18-277, SBD18-279, SBD19-02 and SBD19-57) were characterized. Fungal mycelia were initially grayish white and then gradually changed to gray to dark gray on PDA at 25oC, and later produced black pigments (Fig. S1). Pycnidia were observed from inoculated strawberries at 14 d. Isolates shared similar conidia morphology: aseptate, hyaline, ellipsoid to ovoid, measuring L × W: 24.0-34.0 (28.3) × 13.0-16.0 (14.3) µm (n =100). Mature conidia were brown, one septate, measuring L × W: 25.0-33.0 (28.8) × 13.0-16.0 (14.5) µm (n =100). The isolates were identified as Lasiodiplodia spp. morphologically (Alves et al. 2008). DNA was extracted from fungal mycelia using an OmniPrep DNA extraction kit, and PCR amplification of ITS and EF1-α genes was performed following the conditions described by White et al. (1990) with some modifications using primers ITS1F-F/ITS4-R (Gardes and Bruns, 1993; White et al., 1990) and EF1-668-F/EF1-1251-R (Alves et al., 2008), respectively. The BLASTn in GenBank showed that the sequences obtained had 99.61 to 100% homology with those of ITS (EF622077) and EF1-α (EF622057) from L. pseudotheobromae CBS116459 (an ex-type strain) (Alves et al., 2008). Sequences of the isolates have been deposited in GenBank with accessions OP326017 to OP326021 for ITS, and OP356202 to OP356206 for EF1-α. Phylogenetic analysis showed that these isolates clustered in the same clade (bootstrap value at 64) with L. pseudotheobromae (Fig. S2). Two fungal inoculum types (mycelia and conidia), two fruit inoculation methods (injury and non-injury) and five fungal isolates were used for pathogenicity tests. Fungal mycelia (2-day-old) on PDA plug (5 mm) or 10 µL of conidial suspension (106 spores/mL) was placed onto each injury (1 x 1 mm in size) or a non-injury area on the surfaces of five strawberry fruits (cv. Florida Brilliance). PDA plug alone or water drops placed on injury or non-injury areas on fruits served as respective controls. Inoculated and control fruits were incubated in a covered plastic container with 100% RH at 22ºC. The experiment was repeated twice. Decay initially appeared as soft and lightly discolored tissue at inoculation areas 2 d post-inoculation (dpi) that extended quickly thereafter. Brown to dark lesions on both injury- and non-injury fruits inoculated with conidia or mycelia were observed at 3 dpi. Decay and gray mycelia gradually developed over the whole fruit at 6 dpi, and pycnidia were observed after 14 dpi (Fig. S1). Disease incidence of 100% was observed on all tests. Control fruits did not develop decay. The results indicate that these isolates are pathogenic to strawberries and infect fruit via both non-injured and injured fruit surfaces. The inoculated fungal isolates were re-isolated, thus, fulfilling Koch's postulates. L. theobromae, Neofusicoccum parvum/N. ribis species complex causing strawberry fruit rot in Florida fields was reported (Oliveira et al., 2019), but not L. pseudotheobromae. To our knowledge, this is the first report of postharvest decay caused by L. pseudotheobromae A.J.L. Phillips, A. Alves & Crous on strawberries in Florida and in the USA, and it should be considered in strawberry disease management.

The Potential of Gaseous Chlorine Dioxide for the Control of Citrus Postharvest Stem-End Rot Caused by Lasiodiplodia theobromae.

The focus of this study was to develop technologies using chlorine dioxide (ClO2) gas to control postharvest stem-end rot of citrus caused by Lasiodiplodia theobromae. Mycelial growth of L. theobromae on potato dextrose agar (PDA) plugs was completely inhibited by a 24-h ClO2 exposure provided by 0.5 g of solid ClO2 generating granular mixture in a 7.7-liter sealed container. In vivo experiments were conducted on artificially inoculated Tango and naturally infected U.S. Early Pride mandarins. When ClO2 treatments were initiated 0 to 6 h after inoculation, decay development was significantly reduced as compared with the control, and higher ClO2 doses were more effective. A ClO2 treatment (using 3 g of generating mixture per 7.7-liter sealed container) administered 0 h after inoculation resulted in 17.6% Diplodia stem-end rot incidence compared with 95.6% in the control, whereas the same treatment administered 24 h after inoculation was much less effective, resulting in 63.0% incidence compared with 85.4% in the control. Diplodia stem-end rot incidence of naturally infected fruit after using 6 or 9 g of generating mixture per 24-liter sealed box was 23.8 or 25.7%, respectively, compared with 47.9% for control fruit. The ClO2 treatments had no negative effects on fruit quality characteristics including weight loss, firmness, puncture resistance, titratable acids (TAs), total soluble solids (TSSs), and rind color. Albedo pH at wounds was significantly reduced from 6.0 to 4.8 by the ClO2 treatments, whereas undamaged albedo remained at 5.8. In addition, no visible physiologic defects, such as peel browning and bleaching, were observed on ClO2-treated fruit. These results indicate that ClO2 gas has the potential to be developed as a component of an integrated citrus postharvest decay control system to minimize fruit losses.

A brief hot-water treatment alleviates chilling injury symptoms in fresh tomatoes.

BACKGROUND: Reducing the negative effects of chilling injury (CI) in tomatoes after harvest is essential to ensure good quality and to minimize losses. CI is a postharvest disorder associated with the generation of reactive oxygen species (ROS) in the fruit. Therefore, antioxidant accumulation can counteract ROS, alleviating CI symptoms. In this sense, it has been confirmed that a brief hot-water (HW) immersion promotes the synthesis of antioxidants. RESULTS: HW treatment at 52 °C for 5 min significantly reduced chilling-associated decay, from 66.7% to 17.2% in breaker turning (BT) and from 55.8% to 9.8% in mature green (MG) 'BHN-602' tomatoes stored at 5 °C for 2 weeks and from 26.7% to 6.7% in BT tomatoes stored at 5 °C for 1 week. Also, HW treatment significantly increased lycopene content by 17% in BT tomatoes stored at 5 °C for 2 weeks, as well as ascorbic acid by 11%, lipophilic phenolics by 18% and total phenolics by 6.5% in BT tomatoes stored at 12.5 °C for 1 week. Despite the increase of antioxidants, HW treatment did not enhance the sensory aromatic profile, color and antioxidant capacity. Interestingly, HW treatment reduced ripening time by 3 days in MG tomatoes stored at 5 °C for 2 weeks or at 12.5 °C for 1 week. CONCLUSION: HW treatment applied to MG or BT 'BHN-602' tomatoes can alleviate the development of some CI symptoms, particularly decay, possibly by increasing antioxidants that scavenge ROS. © 2020 Society of Chemical Industry.

Stereoselective Electro-2-deoxyglycosylation from Glycals.

We report a novel and highly stereoselective electro-2-deoxyglycosylation from glycals. This method features excellent stereoselectivity, scope, and functional-group tolerance. This process can also be applied to the modification of a wide range of natural products and drugs. Furthermore, a scalable synthesis of glycosylated podophyllotoxin and a one-pot trisaccharide synthesis through iterative electroglycosylations were achieved.

Deficiency of valencene in mandarin hybrids is associated with a deletion in the promoter region of the valencene synthase gene.

BACKGROUND: Valencene is a major sesquiterpene in citrus oil and biosynthesized by valencene synthase (Cstps1; EC: 4.2.3.73) from the 15-carbon substrate farnesyl diphosphate. It is abundant in juice of some mandarins (e.g. Citrus reticulata Blanco cv. Fortune), however, it is undetectable in others (e.g. C. reticulata Blanco cv. Murcott), We have discovered that the Murcott mandarin Cstps1 gene expression is severely reduced. A previous genetic mapping study using an F1 population of Fortune × Murcott found that the segregation of valencene production in fruit exhibited a Mendelian inheritance ratio of 1:1. There was only one dominant locus associated with valencene content detected on the mandarin genetic map. The goal of this study was to understand the molecular mechanism underlying the valencene deficiency observed in some citrus hybrids. RESULTS: There was a clear relationship between presence or absence of the valencene synthase gene (Cstps1) expression, and presence or absence of valencene among randomly selected mandarin hybrids. Cloning the coding regions of Cstps1 from Fortune and Murcott mandarin, and aligning with previous reported Valencia orange Cstps1 sequence, showed that they both exhibited extremely high similarity with the known Cstps1. By further cloning and analyzing the promoter region of Cstps1 from Valencia, Fortune and Murcott, a 12-nucleotide deletion at approximately - 270 bp from the Cstps1 coding region was only found in Murcott. Three binary vectors, designated as p1380-FortP-GUSin, p1380-MurcP-GUSin and p1380-MurcP(+ 12)-GUSin, were developed for promoter activity analysis. Transient over-expression of Fortune Cstps1 promoter in sweet orange showed notable GUS activity, but the Murcott Cstps1 promoter did not. In addition, by re-inserting the 12-nucleotide fragment, the activity of the Murcott Cstps1 promoter was mostly recovered. CONCLUSION: The deficiency of valencene production in some mandarins is probably due to a 12-nucleotide deletion in the promoter region of the Cstps1, which could be a crucial switch of Cstps1 transcription. Our results further enhanced the understanding of valencene biosynthesis in citrus.

Distribution of Volatile Compounds in Different Fruit Structures in Four Tomato Cultivars.

Distribution of volatile compounds in different fruit structures were analyzed in four tomato cultivars by headspace-solid-phase microextraction (SPME)-gas chromatography-mass spectrometry (GC-MS). A total of 36 volatile compounds were identified in fruit samples, which were primarily aldehydes, hydrocarbons, alcohols, ketones, furans, esters, nitrogen compounds, and sulfur and nitrogen-containing heterocyclic compounds. The volatile compositions in pericarp (PE), septa and columella (SC), locular gel and seeds (LS), and stem end (SE) tissues showed different profiles. The PE tissue showed the highest total volatile concentration due to a high abundance of aldehydes, especially cis-3-hexenal and benzaldehyde. Meanwhile, it showed higher aromatic proportion and herbaceous series intensity than other tissues. Floral and fruity series showed higher intensity in SC and LS tissues. The concentration of alcohols in the LS was higher than that in other tissues in association with the higher abundances of 2-methyl propanol, 3-methyl butanol, and 2-methyl butanol. However, the numbers and concentrations of volatile compounds, especially cis-3-hexenal, benzaldehyde, and geranyl acetone were lower in SE than in the other tissues, indicating less tomato aromas in SE. SE tissues were also lacking in floral and fruity characteristic compounds, such as geranyl acetone, 1-nitro-pentane, and 1-nitro-2-phenylethane. "FL 47" contained more volatile compounds than the other three, and the contents of aldehydes, ketones and oxygen-containing heterocyclic compounds in the "Tygress" fruit were higher than the other cultivars.

Comparative analysis of juice volatiles in selected mandarins, mandarin relatives and other citrus genotypes.

BACKGROUND: Citrus fruit flavor is an important attribute prioritized in variety improvement. The present study compared juice volatiles compositions from 13 selected citrus genotypes, including six mandarins (Citrus reticulata), three sour oranges (Citrus aurantium), one blood orange (Citrus sinensis), one lime (Citrus limonia), one Clementine (Citrus clementina) and one satsuma (Citrus unshiu). RESULTS: Large differences were observed with respect to volatile compositions among the citrus genotypes. 'Goutou' sour orange contained the greatest number of volatile compounds and the largest volatile production level. 'Ponkan' mandarin had the smallest number of volatiles and 'Owari' satsuma yielded the lowest volatile production level. 'Goutou' sour orange and 'Moro' blood orange were clearly distinguished from other citrus genotypes based on the analysis of volatile compositions, even though they were assigned into one single group with two other sour oranges by the molecular marker profiles. CONCLUSIONS: The clustering analysis based on the aroma volatile compositions was able to differentiate mandarin varieties and natural sub-groups, and was also supported by the molecular marker study. The gas chromatography-mass spectrometry analysis of citrus juice aroma volatiles can be used as a tool to distinguish citrus genotypes and assist in the assessment of future citrus breeding programs. The aroma volatile profiles of the different citrus genotypes and inter-relationships detected among volatile compounds and among citrus genotypes will provide fundamental information on the development of marker-assisted selection in citrus breeding. © 2017 Society of Chemical Industry.

Identification of QTLs controlling aroma volatiles using a 'Fortune' x 'Murcott' (Citrus reticulata) population.

BACKGROUND: Flavor is an important attribute of mandarin (Citrus reticulata Blanco), but flavor improvement via conventional breeding is very challenging largely due to the complexity of the flavor components and traits. Many aroma associated volatiles of citrus fruit have been identified, which are directly related to flavor, but knowledge of genetic linkages and relevant genes for these volatiles, along with applicable markers potentially for expeditious and economical marker-assisted selection (MAS), is very limited. The objective of this project was to identify single nucleotide polymorphism (SNP) markers associated with these volatile traits. RESULT: Aroma volatiles were investigated in two mandarin parents ('Fortune' and 'Murcott') and their 116 F1 progeny using gas chromatography mass spectrometry in 2012 and 2013. A total of 148 volatiles were detected, including one acid, 12 alcohols, 20 aldehydes, 14 esters, one furan, three aromatic hydrocarbons, 16 ketones, one phenol, 27 sesquiterpenes, 15 monoterpenes, and 38 unknowns. A total of 206 quantitative trait loci (QTLs) were identified for 94 volatile compounds using genotyping data generated from a 1536-SNP Illumina GoldenGate assay. In detail, 25 of the QTLs were consistent over more than two harvest times. Forty-one QTLs were identified for 17 aroma active compounds that included 18 sesquiterpenes and were mapped onto four genomic regions. Fifty QTLs were for 14 monoterpenes and mapped onto five genomic regions. Candidate genes for some QTLs were also identified. A QTL interval for monoterpenes and sesquiterpenes on linkage group 2 contained four genes: geranyl diphosphate synthase 1, terpene synthase 3, terpene synthase 4, and terpene synthase 14. CONCLUSIONS: Some fruit aroma QTLs were identified and the candidate genes in the terpenoid biosynthetic pathway were found within the QTL intervals. These QTLs could lead to an efficient and feasible MAS approach to mandarin flavor improvement.

Identification of a methyltransferase catalyzing the final step of methyl anthranilate synthesis in cultivated strawberry.

BACKGROUND: Methyl anthranilate (MA) contributes an attractive fruity note to the complex flavor and aroma of strawberry (Fragaria spp.), yet it is rare in modern cultivars. The genetic basis for its biosynthesis has not been elucidated. Understanding the specific genes required for its synthesis could allow  the development of gene/allele-specific molecular markers to speed breeding of flavorful strawberries. RESULTS: Ripe fruits from individuals in an F1 population resulting from a cross between a MA producer and a non-producer were examined using a bulk-segregant transcriptome approach. MA producer and non-producer transcriptomes were compared, revealing five candidate transcripts that strictly co-segregated with MA production. One candidate encodes an annotated methyltransferase. MA levels are lower when this transcript is suppressed with RNAi, and bacterial cultures expressing the protein produced MA in the presence of anthranilic acid. Frozen fruit powders reconstituted with anthranilic acid and a methyl donor produced MA only if the transcript was detected in the fruit powder. A DNA-based molecular marker was developed that segregates with the MA-producing gene variant. CONCLUSIONS: These analyses indicate that the methyltransferase, now noted ANTHRANILIC ACID METHYL TRANSFERASE (FanAAMT), mediates the ultimate step of MA production in cultivated strawberry. Identification of this gene and its associated molecular marker may hasten breeding efforts to introduce this important volatile into modern cultivars.

Effects of thermal processing and pulp filtration on physical, chemical and sensory properties of winter melon juice.

BACKGROUND: Winter melon (Benincasa hispida) is a widely consumed crop in Asia, and believed to impart special benefits to human health. The nutritional composition and sensory properties of four juice types, resulting from a combination of pulp levels (low/high pulp, LP/HP) and thermal processing (with/without boiling, B/NB), LPNB, HPNB, LPB and HPB, were compared. RESULTS: The juices had low sugars (< 20 g kg-1 ) and low titratable acidity (about 2 g kg-1 ). The insoluble solids, glucose, fructose and citric acid content in LP juice were significantly lower than in HP juice. The phenolic amino acids phenylalanine, tyrosine, and tryptophan were detected at 10-45 mg L-1 levels, and the antioxidant activity ranged from 36 to 49 mg gallic acid L-1 . C6 and C9 aldehydes were mainly found in HP juice, and boiling induced the accumulation of sulfur compounds and C5 aldehydes. The LPNB juice showed the highest acceptability in the sensory panel. The frozen concentrated orange juice (FCOJ) reconstituted with LPNB was preferable to regular FCOJ for 31% of panelists and not different for 20% of panelists. CONCLUSION: The low sugar/low acid LPNB juice with 'fresh' flavor could be developed to replace water for reconstituting FCOJ with enhanced nutritional value. © 2016 Society of Chemical Industry.

Development of delayed bitterness and effect of harvest date in stored juice from two complex citrus hybrids.

BACKGROUND: Mandarins and mandarin hybrids have excellent flavor and color attributes, making them good candidates for consumption as fresh fruit. When processed into juice, however, they are less palatable, as they develop delayed bitterness when stored for a period of time. In this study the kinetics of delayed bitterness in two citrus mandarin hybrid siblings, 'Ambersweet' and USDA 1-105-106, was explored by sensory and instrumental analyses. In addition to the bitter limonoids, other quality factors (i.e. sugars, acids, pH, soluble solids content (SSC), titratable acidity (TA) and the ratio SSC/TA) were also measured. RESULTS: The two citrus hybrid siblings had different chemical profiles, which were perceived by taste panels. USDA 1-105-106 developed delayed bitterness when the juice was stored for more than 4 h, similar to juice from 'Navel' oranges, but 'Ambersweet' did not. Bitterness in 'Ambersweet' was more affected by harvest maturity, as juice from earlier harvest had lower SSC but higher TA and bitter limonoids. CONCLUSION: Since juice of USDA 1-105-106 shows delayed bitterness when stored for more than 4 h, this cultivar is not suitable for juice processing. Our finding that siblings can differ in chemical and sensory properties emphasize the importance of post-processing storage studies before releasing cultivars for juice.

Proteomic and metabolomic analyses provide insight into production of volatile and non-volatile flavor components in mandarin hybrid fruit.

BACKGROUND: Although many of the volatile constituents of flavor and aroma in citrus have been identified, the knowledge of molecular mechanisms and regulation of volatile production are very limited. Our aim was to understand mechanisms of flavor volatile production and regulation in mandarin fruit. RESULT: Fruits of two mandarin hybrids, Temple and Murcott with contrasting volatile and non- volatile profiles, were collected at three developmental stages. A combination of methods, including the isobaric tags for relative and absolute quantification (iTRAQ), quantitative real-time polymerase chain reaction, gas chromatography, and high-performance liquid chromatography, was used to identify proteins, measure gene expression levels, volatiles, sugars, organic acids and carotenoids. Two thirds of differentially expressed proteins were identified in the pathways of glycolysis, citric acid cycle, amino acid, sugar and starch metabolism. An enzyme encoding valencene synthase gene (Cstps1) was more abundant in Temple than in Murcott. Valencene accounted for 9.4% of total volatile content in Temple, whereas no valencene was detected in Murcott fruit. Murcott expression of Cstps1 is severely reduced. CONCLUSION: We showed that the diversion of valencene and other sesquiterpenes into the terpenoid pathway together with high production of apocarotenoid volatiles might have resulted in the lower concentration of carotenoids in Temple fruit.

High incidence of preharvest colonization of huanglongbing-symptomatic citrus sinensis fruit by Lasiodiplodia theobromae (Diplodia natalensis) and exacerbation of postharvest fruit decay by that fungus.

Huanglongbing (HLB), presumably caused by the bacterium "Candidatus Liberibacter asiaticus," is a devastating citrus disease associated with excessive preharvest fruit drop. Lasiodiplodia theobromae (diplodia) is the causal organism of citrus stem end rot (SER). The pathogen infects citrus fruit under the calyx abscission zone (AZ-C) and is associated with cell wall hydrolytic enzymes similar to plant enzymes involved in abscission. By means of DNA sequencing, diplodia was found in "Ca. Liberibacter asiaticus"-positive juice from HLB-symptomatic fruit (S) but not in "Ca. Liberibacter asiaticus"-negative juice. Therefore, the incidence of diplodia in fruit tissues, the impact on HLB-related postharvest decay, and the implications for HLB-related preharvest fruit drop were investigated in Hamlin and Valencia oranges. Quantitative PCR results (qPCR) revealed a significantly (P < 0.001) greater incidence of diplodia in the AZ-C of HLB-symptomatic (S; "Ca. Liberibacter asiaticus" threshold cycle [CT] of <30) than in the AZ-C of in asymptomatic (AS; "Ca. Liberibacter asiaticus" CT of ≥30) fruit. In agreement with the qPCR results, 2 weeks after exposure to ethylene, the incidences of SER in S fruit were 66.7% (Hamlin) and 58.7% (Valencia), whereas for AS fruit the decay rates were 6.7% (Hamlin) and 5.3% (Valencia). Diplodia colonization of S fruit AZ-C was observed by scanning electron microscopy and confirmed by PCR test and morphology of conidia in isolates from the AZ-C after surface sterilization. Diplodia CT values were negatively correlated with ethylene production (R = -0.838 for Hamlin; R = -0.858 for Valencia) in S fruit, and positively correlated with fruit detachment force (R = 0.855 for Hamlin; R = 0.850 for Valencia), suggesting that diplodia colonization in AZ-C may exacerbate HLB-associated preharvest fruit drop.

Electronic Tongue Response to Chemicals in Orange Juice that Change Concentration in Relation to Harvest Maturity and Citrus Greening or Huanglongbing (HLB) Disease.

In an earlier study, an electronic tongue system (e-tongue) has been used to differentiate between orange juice made from healthy fruit and from fruit affected by the citrus greening or Huanglongbing (HLB) disease. This study investigated the reaction of an e-tongue system to the main chemicals in orange juice that impact flavor and health benefits and are also impacted by HLB. Orange juice was spiked with sucrose (0.2-5.0 g/100 mL), citric acid (0.1%-3.0% g/100 mL) and potassium chloride (0.1-3.0 g/100 mL) as well as the secondary metabolites nomilin (1-30 µg/mL), limonin (1-30 µg/mL), limonin glucoside (30-200 µg/mL), hesperidin (30-400 µg/mL) and hesperetin (30-400 µg/mL). Performance of Alpha MOS sensor sets #1 (pharmaceutical) and #5 (food) were compared for the same samples, with sensor set #1 generally giving better separation than sensor set #5 for sucrose, sensor set #5 giving better separation for nomilin and limonin, both sets being efficient at separating citric acid, potassium chloride, hesperitin and limonin glucoside, and neither set discriminating hesperidin efficiently. Orange juice made from fruit over the harvest season and from fruit harvested from healthy or HLB-affected trees were separated by harvest maturity, disease state and disease severity.

Identification of a strawberry flavor gene candidate using an integrated genetic-genomic-analytical chemistry approach.

BACKGROUND: There is interest in improving the flavor of commercial strawberry (Fragaria × ananassa) varieties. Fruit flavor is shaped by combinations of sugars, acids and volatile compounds. Many efforts seek to use genomics-based strategies to identify genes controlling flavor, and then designing durable molecular markers to follow these genes in breeding populations. In this report, fruit from two cultivars, varying for presence-absence of volatile compounds, along with segregating progeny, were analyzed using GC/MS and RNAseq. Expression data were bulked in silico according to presence/absence of a given volatile compound, in this case γ-decalactone, a compound conferring a peach flavor note to fruits. RESULTS: Computationally sorting reads in segregating progeny based on γ-decalactone presence eliminated transcripts not directly relevant to the volatile, revealing transcripts possibly imparting quantitative contributions. One candidate encodes an omega-6 fatty acid desaturase, an enzyme known to participate in lactone production in fungi, noted here as FaFAD1. This candidate was induced by ripening, was detected in certain harvests, and correlated with γ-decalactone presence. The FaFAD1 gene is present in every genotype where γ-decalactone has been detected, and it was invariably missing in non-producers. A functional, PCR-based molecular marker was developed that cosegregates with the phenotype in F1 and BC1 populations, as well as in many other cultivars and wild Fragaria accessions. CONCLUSIONS: Genetic, genomic and analytical chemistry techniques were combined to identify FaFAD1, a gene likely controlling a key flavor volatile in strawberry. The same data may now be re-sorted based on presence/absence of any other volatile to identify other flavor-affecting candidates, leading to rapid generation of gene-specific markers.

Postharvest Management of Fruits and Vegetables-Series II.

Fruits and vegetables are crucial nutritional sources of carbohydrates, protein, minerals, vitamins, and dietary fiber, offering significant benefits to human health [...].

Chemical and genetic basis of orange flavor.

Sweet orange (Citrus sinensis) exhibits limited genetic diversity and high susceptibility to Huanglongbing (HLB). Breeding HLB-tolerant orange-like hybrids is in dire need. However, our understanding of the key compounds responsible for orange flavor and their genetic regulation remains elusive. Evaluating 179 juice samples, including oranges, mandarins, Poncirus trifoliata, and hybrids, distinct volatile compositions were found. A random forest model predicted untrained samples with 78% accuracy and identified 26 compounds crucial for orange flavor. Notably, seven esters differentiated orange from mandarin flavor. Cluster analysis showed six esters with shared genetic control. Differential gene expression analysis identified C. sinensis alcohol acyltransferase 1 (CsAAT1) responsible for ester production in orange. Its activity was validated through overexpression assays. Phylogeny revealed the functional allele was inherited from pummelo. A SNP-based DNA marker in the coding region accurately predicted phenotypes. This study enhances our understanding of orange flavor compounds and their biosynthetic pathways and expands breeding options for orange-like cultivars.

Effect of extraction, pasteurization and cold storage on flavonoids and other secondary metabolites in fresh orange juice.

BACKGROUND: Fresh orange juice is perceived to be more wholesome than processed juice. Fresh juice may have nutrients and phytonutrients that differ from pasteurized or processed juice. RESULTS: 'Hamlin' and 'Valencia' oranges were extracted using a commercial food service juicer, pasteurized or not, resulting in fresh-commercial juice (FCJ) or pasteurized FCJ (FCPJ) for comparison with pasteurized processed juice (PPJ) in 2009, and gently hand-squeezed 'Valencia' juice (HSJ) in 2010 for nutrient and phytonutrient content. Regardless of pasteurization, FCJ/FCPJ contained 25-49% lower insoluble solids than the PPJ, while in HSJ the insoluble solids content was between that of FCJ and PPJ. The major orange juice flavonoid glycosides were twofold higher in PPJ than in FCJ/FCPJ and HSJ, indicating that the extraction and finishing process led to more peel tissue in the juice than fresh juice extraction methods. The total phenolic content (TPC) in the juices followed a similar pattern to the flavonoid glycoside content. The polymethoxylated flavones (PMFs), associated with peel oil, occurred at the highest levels in the FCJ/FCPJ and lowest in HSJ. Limonoids and alkaloids occurred at higher levels in PPJ and HSJ than in FCJ/FCPJ. CONCLUSION: The high peel oil content of FCJ/FCPJ resulted in higher PMF levels compared to PPJ and HSJ, while flavonoid glycosides, limonoids and alkaloids, which occur at high concentrations in the inner peel albedo, occurred at higher concentrations in PPJ.

Soil Amendment and Storage Effect the Quality of Winter Melons (Benincasa hispida (Thunb) Cogn.) and Their Juice.

Winter melon fruits were grown in the field using anaerobic soil disinfestation (ASD) and conventional fertilizer alone as the control treatment. Fruits were harvested and stored at 20 °C for 120 d, the juice was processed on day one and day 120, and the effects of soil amendment and 120 d storage on the juice's physical and chemical (sugars, acids, volatile and nutritional compounds) properties were evaluated. Fruit juice extracted from ASD-grown fruit had greater magnitude of zeta potential than the control juice, indicating it was physically more stable than the juice obtained from the control conditions. ASD fruit juice had lower soluble solids content (SSC), and lower volatile compounds that contribute green, grass, and sulfur notes, and negatively influence flavor quality. ASD fruit juice had higher vitamin B5 and cytidine. Juice processed from 120 d stored fruit had less yield due to 12.4-15.6% weight loss. The non-soluble solids content was higher and particle size was larger, and the SSC and individual sugars decreased. However, titratable acidity (TA) increased primarily due to increased citric acid. Out of 16 free amino acids, 6 increased and only 1 decreased. However, three out of five nucleosides decreased; vitamins B1 and B6 increased; vitamins B2, B3 and C decreased. Overall, juice derived from fruit produced using ASD was physically more stable and had less SSC and off-odor volatiles than the control, while the fruit juice of those stored for 120 d had lower SSC and higher TA and nutritional profiles, comparable to freshly harvested fruit.