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This study focused on the identification of rot-causing fungi in Citrus  ×  tangelo (tangelo) with a particular emphasis on investigating the inhibitory effects of acidic electrolyzed water on the identified pathogens. The dominant strains responsible for postharvest decay were isolated from infected tangelo fruits and characterized through morphological observation, molecular identification, and pathogenicity detection. Two strains were isolated from postharvest diseased tangelo fruits, cultured and morphologically characterized, and had their gene fragments amplified using primers ITS1 and ITS4. The results revealed the rDNA-ITS sequence of two dominant pathogens were 100% homologous with those of Penicillium citrinum and Aspergillus sydowii . These isolated fungi were confirmed to induce tangelo disease, and subsequent re-isolation validated their consistency with the inoculum. Antifungal tests demonstrated that acidic electrolyzed water (AEW) exhibited a potent inhibitory effect on P. citrinum and A. sydowii , with EC 50 values of 85.4 μg/mL and 60.12 μg/mL, respectively. The inhibition zones of 150 μg/mL AEW to 2 kinds of pathogenic fungi were over 75 mm in diameter. Furthermore, treatment with AEW resulted in morphological changes such as bending and shrinking of the fungal hyphae surface. In addition, extracellular pH, conductivity, and absorbance at 260 nm of the fungi hypha significantly increased post-treatment with AEW. Pathogenic morphology and IST sequencing analysis confirmed P. citrinum and A. sydowii as the primary pathogenic fungi, with their growth effectively inhibited by AEW.

In the framework of our studies on Citrus cultivars in Greece, the chemical composition of the essential oils (EOs) from the peels and leaves of orange, pummelo, and tangelo (mandarin × grapefruit hybrid) cultivated in Greece have been studied. All EOs have been analyzed through GC-MS, and a total of 47 and 87 metabolites were identified in the peels and leaves, respectively. These metabolites are classified into the chemical groups of terpenes, alcohols, aldehydes, esters, ketones, and organic acids. Limonene was the most abundant compound in the peel EOs. Moreover, bioactive polymethoxyflavones (PMFs) were isolated and structurally determined from the peels of orange and tangelo, highlighting them as a good potential source of natural PMFs. All EOs were evaluated for their antimicrobial activity against nine human pathogenic microorganisms (six bacteria and three fungi), showing an interesting profile. The EOs from the peels of all Citrus species exhibited a stronger antimicrobial activity compared to those from the leaves. The susceptibility of the assayed Gram-positive bacteria was observed to be greater than that of Gram-negative bacteria, while the fungi were also relatively less resistant than bacteria. The rootstock choice did not influence the EO profile of the fruit peel but exerted an influence on the chemical profile of the leaves.

Orlando tangelos are highly susceptible to low temperatures, which can cause chilling injury and result in significant peel depressions that make them unsuitable for commercial purposes. Melatonin and γ-aminobutyric acid (GABA) act as an eco-friendly treatment to improve plant reactions to stress factors. The impact of melatonin, GABA, and their co-application (melatonin + GABA) on chilling tolerance and postharvest quality of Orlando tangelo fruit was investigated throughout the cold storage (90 days at 3 ± 0.5 °C plus 5 days at 20 °C, shelf life). The results of the study indicated that the application of treatments significantly enhanced the chilling tolerance of Orlando tangelo fruit as compared to the untreated fruit. Fruits treated with melatonin + GABA did not exhibit indications of chilling until 90 days after storage. At this stage, the chilling injury of the control fruits was approximately 84.3% greater than those treated with melatonin + GABA. In addition, the treated fruits exhibited a reduced weight loss and malondialdehyde (MDA) concentration compared to the control. The study showed that fruits treated with melatonin exhibited a significantly increased (2.09 mg/g) total phenol content compared to the control (1.34 mg/g) fruits. All treatments significantly enhanced the flavonoid, antioxidant capacity, peroxidase (POD), and catalase (CAT) activity of the fruit compared to the control. A co-application of GABA and melatonin had a more significant impact on protecting the quality of the fruit during cold storage compared to using each treatment separately.

Citrus chlorotic dwarf disease (CCDD) has been associated with loss of productivity in citrus species. Especially in the grapefruit species this loss can reach up to 50%. The causative agent for the disease is Citrus chlorotic dwarf associated virus. Some species in the citrus family can develop resistance to the virus and overcome the symptoms associated with the disease but in those cases they may act as the source of the virus to the surrounding citrus species. Virus management studies mainly focus on the introgression of available virus resistance genes into valuable plant cultivars. In this study, we focused host based aspect of the resistance against the virus. Clementine mandarin × Minneola tangelo hybrid population was created in the Alata Horticultural Research Institute field in 2008. This population showed a resistance to the disease development and we analyzed 186 individuals with a total of 2806 markers. DArT-SNP markers were utilized for the mapping studies. According to our results 9 linkage groups were obtained for Clementine and Minneola. The total length of these groups was 798.70 cm for Clementine and 423.7 cm for Minneola. The total number of markers in the linkage groups was 1536 for Clementine and 1270 for Minneola. The average distance between two markers was 0.51 cm and 0.33 cm for Clementine and Minneola, respectively. 15 QTL loci (with LOD ≥ 3) were associated with CCDD resistance. All of these QTLs’ were specifically determined in Clementine linkage map on LG2, LG3, LG5, LG6 and LG8. Host based genetic characteristics that enable the resistance to the disease were identified by QTL based analysis. These results can pave the way of genetic screening of the resistant versus vulnerable species as well as individuals within the species. Moreover, based on this data genetic manipulations or hybridizations based on the genetic markers can be considered in the future to increase the productivity and to decrease the losses associated with CCDD.

Background The significant rise in antibiotic resistance has become an alarming situation urging the search for new antibacterial agents. Nature has always been a limitless source of bioactives with high safety profile. This study evaluates the antibacterial activity of essential oils from the leaves and fruit peels of Minneola tangelo cultivated in Egypt. In vitro cytotoxicity assay was conducted to ensure the safety profile of the active essential oils. Methods The antibacterial activity of clinical isolates of Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus was assessed using the Kirby-Bauer disk diffusion method. Chemical profiling of the leaf and peel essential oils was performed using GC-MS. In vitro cytotoxicity assay of the leaf essential oil was conducted using sulforhodamine B assay. In silico docking study was conducted to explore the possible antibacterial mechanisms. Results The leaf essential oil exhibited antibacterial activity against the tested isolates, whereas the peel oil was inactive. GC-MS analysis showed differences in the chemical composition of the leaf and fruit peel oils, where 60% of the leaf oil is dominated by linalool (31.6%), cis -β-ocimene (16.1%), and γ-terpinene (14.3%), whereas the fruit peel oil is solely dominated by D-limonene (82%). Cytotoxicity assay on Caco-2 cell line showed IC 50 value of 277.36 µg/mL while that on fibroblast HFB4 cell line was > 1000 µg/mL. In silico studies revealed high affinity of linalool to FabI, a crucial enzyme in the fatty acid biosynthesis pathway of MRSA as well as an affinity to Penicillin binding protein PBP2a. Binding of linalool to shikimate kinase of Acinetobacter baumannii was also demonstrated. Conclusion Essential oil of M. tangelo is a promising antibacterial agent against multidrug resistant strains with a high safety profile. Graphical abstract

Orlando tangelo fruits, originating from tropical and subtropical regions, have demonstrated a tendency to be susceptible to chilling injury when subjected to cold storage conditions. This study investigated the effects of methyl jasmonate (MeJA) (50 µM), γ-aminobutyric acid (GABA) (5 mM), and MeJA (50 µM) + GABA (5 mM) on chilling injury of Orlando tangelo fruits throughout cold storage (90 days at 3 ± 0.5 °C plus 5 days at 20 °C, shelf life). The findings demonstrated that all treatments considerably decreased fruit weight loss. Although all treatments significantly decreased chilling injury, MeJA treatment resulted in the least amount of chilling injury. Malonaldehyde was also significantly lower in the treated fruits in comparison to the control. Maximum phenol and flavonoid were observed in the MeJA treatment, which was 1.47 and 1.63 times higher than the control fruit, respectively. On average, the antioxidant activity of the treatments was 1.33 times higher than that of the control. The treatments increased the activity of catalase (CAT) and peroxidase (POD) enzymes in fruit juice and peel. Whereas, the highest activity of CAT and POD enzymes in the peel was observed in the treatments of MeJA and MeJA + GABA, respectively. Compared to other treatments, MeJA significantly increased the activity of the CAT enzyme in the fruit peel. Even though MeJA exhibited a more pronounced positive effect, the overall results indicate that both individual treatments and MeJA + GABA could be utilized to enhance the cold tolerance of Orlando tangelo fruit during extended periods of cold storage. Graphical abstract

The mandarin horticultural group is an important component of world citrus production for the fresh fruit market. This group formerly classified as C. reticulata is highly polymorphic and recent molecular studies have suggested that numerous cultivated mandarins were introgressed by C. maxima (the pummelos). C. maxima and C. reticulata are also the ancestors of sweet and sour oranges, grapefruit, and therefore of all the \"small citrus\" modern varieties (mandarins, tangors, tangelos) derived from sexual hybridization between these horticultural groups. Recently, NGS technologies have greatly modified how plant evolution and genomic structure are analyzed, moving from phylogenetics to phylogenomics. The objective of this work was to develop a workflow for phylogenomic inference from Genotyping By Sequencing (GBS) data and to analyze the interspecific admixture along the nine citrus chromosomes for horticultural groups and recent varieties resulting from the combination of the C. reticulata and C. maxima gene pools. A GBS library was established from 55 citrus varieties, using the ApekI restriction enzyme and selective PCR to improve the read depth. Diagnostic polymorphisms (DPs) of C. reticulata/C. maxima differentiation were identified and used to decipher the phylogenomic structure of the 55 varieties. The GBS approach was powerful and revealed 30,289 SNPs and 8,794 Indels with 12.6% of missing data. 11,133 DPs were selected covering the nine chromosomes with a higher density in genic regions. GBS combined with the detection of DPs was powerful for deciphering the \"phylogenomic karyotypes\" of cultivars derived from admixture of the two ancestral species after a limited number of interspecific recombinations. All the mandarins, mandarin hybrids, tangelos and tangors analyzed displayed introgression of C. maxima in different parts of the genome. C. reticulata/C. maxima admixture should be a major component of the high phenotypic variability of this germplasm opening up the way for association studies based on phylogenomics.

The effects of acid electrolyzed water (AEW) treatment on the storage quality and metabolism of reactive oxygen species (ROS) in Citrus × tangelo (tangelo) were investigated. AEW‐treated tangelos had a lower risk of decay, a higher proportion of consumer‐acceptable fruit, higher total soluble solids (TSS) and titratable acidity (TA) than untreated control fruit. During storage, AEW treatment decreased the cellular respiration rate and ameliorated the increase in cell membrane permeability, decreased superoxide anion radical (O 2 –• ) production, the malondialdehyde (MDA) and hydrogen peroxide (H 2 O 2 ) concentrations, and increased the activity of superoxide dismutase (SOD), catalase (CAT) and ascorbic acid peroxidase (APX). AEW treatment increased the concentrations of the endogenous antioxidant ascorbic acid (AsA) and glutathione (GSH). It appeared that AEW inhibited membrane lipid peroxidation by increasing the ROS scavenging rate and decreasing ROS; overall, AEW treatment was effective in maintaining the quality and storability of postharvest tangelos.

Insect pollinators contribute significantly to global food production impacting both crop yields and quality, but the dependence of specific crops on insect pollinators can vary across production regions and cultivars. The state of Florida has a unique agroecosystem that supports temperate and tropical fruits, vegetables, and nuts, and these specialty crops likely have a high dependence on pollinators. We conducted a systematic review to quantify the role of insect pollinators for Florida agriculture, and to identify crops and cultivars for which recent research on pollination is lacking. For all crops, we determined the average yield losses incurred without insect pollination (“pollinator contribution value”) by synthesizing previously reported values. We found that insect pollinators are required or beneficial for 47 different crops in Florida, or 43% of all plant crop species grown in the state. Major crops in the state with complete to high dependence on insect pollinators include blueberries, mangoes, melons, squashes, and tangelos; for these crops, insect pollinators contribute 75 to 100% of crop productivity. Other major crops in Florida that are moderately to highly dependent on pollinators include avocadoes, cucumbers, field tomatoes, grapefruits, green beans, oranges (select cultivars), peppers, southern peas, and strawberries, with pollinator contributions ranging from 30 to 74%. The contribution of insect pollinators exceeds $50 million per crop per yr in Florida for 7 of its most valuable crops. Using production data at the county level, we found that pollinators contribute to agriculture in almost all Florida counties. Our review identified a number of crops for which little information on pollination requirements exists, especially for modern cultivars. We discuss gaps in our knowledge of crop pollination requirements and recommendations for future research. Estimates of pollinator contributions are invaluable for farm management and policy decisions around pollinator conservation.

Although studies have quantified bacterial transfer between hands and various materials, cross-contamination between the surface of fresh citrus fruit and the edible portions during hand peeling has not been reported. This study quantifies transfer of Salmonella to the edible portion of citrus fruit from a contaminated peel during hand peeling. Citrus fruits used for this study were Citrus sinensis (sweet orange) cultivars 'Valencia' and 'Navel', Citrus unshiu (Satsuma mandarins), Citrus reticulata × Citrus paradisi ('Minneola' tangelo or 'Honeybell'), and C. paradisi (grapefruit) cultivar 'Marsh'. An avirulent Salmonella Typhimurium LT2 (ATCC 700720) resistant to rifampin was used for all experiments. The inoculum containing approximately 9 log CFU/mL (50 μL) was spot inoculated onto the equator, stem, or styler of each fruit and allowed to dry for 24 h. Six volunteers put on single-use latex gloves and peeled inoculated fruit. Peel, edible fruit portion, and gloves were collected and enumerated separately. Three replicates of the study were performed in which each volunteer peeled two inoculated fruit of each variety (n = 36 fruit per variety). Cross-contamination from contaminated surface of citrus fruits to edible portion or gloved hands during peeling was affected by inoculation sites. Average Salmonella transfer to the edible portion ranged from 0.16% (Valencia inoculated at the equator) to 5.41% (navel inoculated at the stem). Average Salmonella transfer to gloved hands ranged from 0.41% (grapefruit inoculated at the stem) to 8.97% (navel inoculated at the stem). Most Salmonella remained on the peel of citrus fruits. The average level of Salmonella remaining on the peel ranged from 5.37% (Minneola inoculated at the equator) to 66.3% (Satsuma inoculated at the styler). When grapefruit was inoculated, the Salmonella that remained on the peel showed a bimodal pattern in which some individuals left almost all Salmonella on the peel, while others left substantially less.