Citrus Spp Research Articles

Pest categorisation of Ceroplastes rubens.

The European Commission requested the EFSA Panel on Plant Health to conduct a pest categorisation of Ceroplastes rubens Maskell (Hemiptera: Coccidae), following the commodity risk assessments of Acer palmatum plants grafted on A. davidii and Pinus parviflora bonsai plants grafted on P. thunbergii from China, in which C. rubens was identified as a pest of possible concern to the European Union (EU). The pest, which is commonly known as the pink, red or ruby wax scale, originates in Africa and is highly polyphagous attacking plants from more than 193 genera in 84 families. It has been present in Germany since 2010 in a single tropical glasshouse. It is known to attack primarily tropical and subtropical plants, but also other host plants commonly found in the EU, such as Malus sylvestris, Prunus spp., Pyrus spp. and ornamentals. It is considered an important pest of Citrus spp. The pink wax scale reproduces mainly parthenogenetically, and it has one or two generations per year. Fecundity ranges from 5 to 1178 eggs. Crawlers settle usually on young twigs and later stages are sessile. All life stages of C. rubens egest honeydew on which sooty mould grows. Host availability and climate suitability suggest that parts of the EU would be suitable for establishment. Plants for planting and cut branches provide the main pathways for entry. Crawlers could spread over short distances naturally through wind, animals, humans or machinery. C. rubens could be dispersed more rapidly and over long distances via infested plants for planting for trade. The introduction of C. rubens into the EU could lead to outbreaks causing damage to orchards, amenity ornamental trees and shrubs. Phytosanitary measures are available to inhibit the entry and spread of this species. C. rubens satisfies the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Ethnobotany and diversity of Citrus spp. (Rutaceae) as a source of “Kem-kem” traditional medicine used among the Karo sub-ethnic in North Sumatra, Indonesia

The Karo sub-ethnic is one of five Batak sub-ethnicities in the Karo Regency, North Sumatra Province, Indonesia. They are famous for their local knowledge about the traditional use of medicinal plants to treat various diseases. The “Kem-kem” traditional medicine is one of the traditional healing practices that involve using plants passed down through generations from their ancestors. One of the plant genus group in the Rutaceae family utilized in the traditional “Kem-kem” healing practice is a citrus known as “Rimo”. This study aims to document the local knowledge about the diversity of Citrus spp. as Kem-kem's herbal medicinal plant. This study was conducted from April to July 2023 in the Kabanjahe and Berastagi districts, Karo Regency, North Sumatra. Data was collected using interviews with traditional healers, herbal medicine vendors, and direct observations at traditional markets, involving a total of 8 Citrus spp. The Karo uses “Rimo” with different local names as sources of traditional medicinal ingredients in practicing “Kem-kem”. There are 15 local names comprising eight species of Citrus. Four are hybrids, i.e., Citrus x aurantiifolia (Christm.) Swingle, Citrus × aurantium L, Citrus × junos Siebold ex Yu.Tanaka, and Citrus × taitensis Risso. Two of the remaining species are recognized in infraspecific rank, one variety (Citrus medica var. sarcodactylis (Hoola van Nooten) Swingle) and one form (Citrus × aurantium f. deliciosa (Ten.) M.Hiroe). They were used as material sources for Kem-kem traditional medicine to treat at least nine health problems. There are two species with six local names included in the Least Concern (LC) category, namely C. medica (Rimo Gawang, Rimo Hantuantu, Rimo Kayu), C. medica var. sarcodactylis (Rimo Kuku Harimau), and C. medica (Rimo Telur Buaya), C. maxima (Burm.) Merr. (Rimo Malem). Nine local names are included in the Not Evaluated (NE) category, namely C. × junos (Rimo Kejaren), C. × taitensis (Rimo Jungga), C. × aurantium f. deliciosa (Rimo Keling), C. × aurantium (Rimo Kersik), Citrus hystrix DC. (Rimo Mukur), C. × taitensis (Rimo Puraga), C. × aurantium (Rimo Kalele), Citrus swinglei Burkill ex Harms (Rimo Pagar), and C. x aurantiifolia (Rimo Bunga). Rimo Kejaren (C. × junos) is a species that has the most benefits.

When sustainability meets health and innovation: The case of Citrus by-products for cancer chemoprevention and applications in functional foods

Peel, pomace and seeds represent secondary products derived from production and manufacturing processes of Citrus spp. However, thanks to the novel policies of circular economy, sustainability and valorization of agro-wastes, Citrus by-products have become a precious source of energy and natural beneficial compounds used for manifold applications, from biofuels to dietary supplements and nutraceuticals, to food additives and bio-preservatives. Several studies have been carried out to investigate the bioactivities, functionalize, stabilize and use these products or part of them (e.g., extracts, oils, powders, purified compounds). In this context, this study discusses properties, technological processing and extraction, functions and health implications of Citrus by-products as cancer chemopreventive agents, and lays a special emphasis on the stabilization, encapsulation and delivering of Citrus by-products phytochemicals and formulations. As the extraction and isolation are key aspects of phytochemicals availability the first objective of this study was to critically examine innovative and non-conventional techniques. Subsequently, to have a comprehensive understanding of bioactivity underlying the complex anticancer actions through various mechanisms, the methods/assays for antiproliferative, proapoptotic, anti-inflammatory, antioxidant activity evaluation were introduced, and the models and biomolecules were presented, using the methodologies of extensive literature search and meta-analysis. Upcoming perspectives and the current and future framework were also discussed.

Una lista comentada de virus de plantas descritos en Paraguay (1920–2023)

Abstract Despite an economy based mostly on agriculture, literature on viral diseases of plants is scarce in Paraguay. Only recently, researches on plant viruses took an impulse resulting in a precise identification of many of them affecting plants either cultivated or not. To provide reliable information regarding plant viruses present in Paraguay, an annotated list of them was prepared, covering descriptions from 1920 to present day. There have been some important outbreaks with severe yield losses in crops as cucurbits, citrus, sesame, bean, maize, peanuts and tomato. Many of older descriptions are included for their historical significance, but most identifications made require confirmation. On the other hand, recent descriptions have been completed, based on several assays, especially molecular characterization. This list is organized alphabetically following scientific names of the plant species found naturally infected by viruses, with comments about symptoms, geographical distribution, incidence, identification procedures, and other information, with due literature references. It is based on a compilation of publications made on plant virus diseases in Paraguay. Described virus species, in a total of 38 recognized by ICTV, belonging to 17 different genera (Alphaendornavirus, Ampelovirus, Begomovirus, Benyvirus, Carlavirus, Cilevirus, Closterovirus, Comovirus, Cucumovirus, Dichorhavirus, Fabavirus, Luteovirus, Ophiovirus, Orthotospovirus, Potexvirus, Potyvirus and Tobamovirus), besides two unclassified, and four unidentified. There is also a case of viroid described in Citrus spp. Infections caused by potyviruses are the most numerous. These viruses were described in more than 40 plant species, belonging to 18 botanical families. Because of crop diversity and richness in native flora, many more viruses must be present in Paraguay, which future works will certainly reveal, especially with the increase in manpower involving researches, especially cooperative with foreign centers, on plant viruses, which has been very limited until now. Also, knowledge on existing viruses may have relevance in understanding their epidemiology and provide the basis for their control strategies and quarantine measures, to avoid new variants of existing viruses or new viruses being introduced.

Auraptene Has Antiviral Activity against Human Coronavirus OC43 in MRC-5 Cells

Auraptene (7-geranyloxycoumarin) is the abundant prenyloxycoumarin found in the fruits of Citrus spp. Auraptene has a variety of pharmacological and therapeutic functions, such as anticancer, antioxidant, immunomodulatory, and anti-inflammation activities, with excellent safety profiles. In this study, we evaluated the anticoronaviral activity of auraptene in HCoV-OC43-infected human lung fibroblast MRC-5 cells. We found that auraptene effectively inhibited HCoV-OC43-induced cytopathic effects with 4.3 μM IC50 and 6.1 μM IC90, resulting in a selectivity index (CC50/IC50) of >3.5. Auraptene treatment also decreased viral RNA levels in HCoV-OC43-infected cells, as detected through quantitative real-time PCR, and decreased the expression level of spike proteins and nucleocapsid proteins in virus-infected cells, as detected through the Western blot analysis and immunofluorescence staining. Time-of-addition analysis showed auraptene’s inhibitory effects at the post-entry stage of the virus life cycle; however, auraptene did not induce the antiviral interferon families, IFN-α1, IFN-β1, and IFN-λ1. Additionally, auraptene-treated MRC-5 cells during HCoV-OC43 infection decreased the MMP-9 mRNA levels which are usually increased due to the infection, as auraptene is a previously reported MMP-9 inhibitor. Therefore, auraptene showed antiviral activity against HCoV-OC43 infection, and we suggest that auraptene has the potential to serve as a therapeutic agent against human coronavirus.

Clonal Expansion in Multiple Phyllosticta Species Causing Citrus Black Spot or Similar Symptoms in China.

Phyllosticta spp. are important pathogens of citrus plants. Several Phyllosticta species associated with Citrus species grown in China have been reported; however, the relative prevalences of individual species and the distributions of their genotypes among host Citrus species remain largely unknown. In this study, we conducted an extensive survey of Phyllosticta species across 11 citrus-producing provinces in southern China. From fruits and leaves with black spots or black-spot-like symptoms, a total of 461 Phyllosticta strains were isolated. Based on molecular (ITS, actA, tef1, gapdh, LSU, and rpb2 sequences) and morphological data, the strains were systematically identified as belonging to five species: P. capitalensis, P. citrichinaensis, P. citriasiana, P. citricarpa, and P. paracitricarpa. To further understand intraspecific genetic diversity and relationships, strains of five species from different geographic and host sources were analyzed based on the multilocus sequence data. Our population genetic analyses revealed that all five Phyllosticta species on citrus showed evidence for clonal dispersals within and among geographic regions. In addition, pathogenicity tests using representative strains showed that all five species can cause disease on the tested Citrus spp. We discuss the implications of our results for the control and management of Citrus Black Spot and related diseases.

Elucidation of Physio-Biochemical Changes in Citrus spp. Incited by Xanthomonas citri pv. citri

India is one of the leading citrus−producing countries, next to China and Brazil. Despite the sizeable production, especially of lemons and limes, India contributes meagerly to the world’s citrus market. Of the various factors responsible for the restricted quantum of citrus export, citrus canker (Xanthomonas citri pv. citri) is one of the leading serious causes and directly impacts the appearance of the fruits. Considering the extent of damage, the present study aimed to understand the impact of Xanthomonas citri pv. citri (Xcc) on the physio−biochemical responses in contrasting Citrus spp. Two genotypes, each of three citrus species, namely Citrus aurantifolia (Pusa Udit and ALC−35), C. limon (Kagzi Kalan and Konkan Seedless), and C. paradisi (Redblush and Marsh Seedless), were artificially inoculated with Xcc (108 to 109 cfu/ mL) by the pinprick method. The physio−biochemical changes in the host were evaluated after 48 h post inoculation (hpi). The chlorophyll content (total, a, and b) degradation and reduction in leaf gas exchange parameters, such as photosynthetic rate (A), transpiration rate (E), stomatal conductance (gs), and intrinsic water−use efficiency (iWUE), were measured to a greater extent in susceptible than resistant genotypes. The microscopic observations also evidenced higher stomatal density with larger stomatal areas in susceptible genotypes, favoring the easier penetration of Xcc in host tissues than resistant species or genotypes. The higher activities of various antioxidant enzymes, viz., superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and glutathione reductase (GR), the contents of soluble protein, and phenolics were measured in resistant genotypes in contrast to susceptible genotypes. The activities of phenyl ammonia lyase (PAL) and polyphenol oxidase (PPO) were also higher in resistant genotypes, whilst the levels of ROS (superoxide radical and hydrogen peroxide) production were enhanced in susceptible genotypes. Based on the host–pathogen interaction, the order of resistance in a descending manner was found as Kagzi Kalan, Marsh Seedless, Redblush, Konkan Seedless, Pusa Udit, and ALC−35. Further, the results will enhance the understanding of the pathogen mechanism during pathogenesis in resistant and susceptible Citrus species.

Evaluation of Cryogen-Free Thermal Modulation-Based Enantioselective Comprehensive Two-Dimensional Gas Chromatography for Stereo-Differentiation of Monoterpenes in Citrus spp. Leaf Oils.

This study evaluates the applicability of enantioselective gas chromatography (eGC) and enantioselective comprehensive two-dimensional gas chromatography (eGC×GC) coupled with flame ionization detection for the stereospecific analysis of designated chiral monoterpenes within essential oils distilled from the leaves of Citrus hystrix (CH), C. limon (CL), C. pyriformis (CP), and C. microcarpa (CM). A cryogen-free solid-state modulator with a combination of enantioselective first-dimension and polar second-dimension column arrangements was used to resolve potential interferences in Citrus spp. leaf oils that can complicate the accurate determination of enantiomeric compositions. Interestingly, considerable variations were observed for the enantiomeric fractions (EFs) of the chiral terpenes. (+)-limonene was identified as the predominant enantiomer (60.3-98.9%) in all Citrus oils, (+)-linalool was the major enantiomer in CM (95.9%), (-)-terpenin-4-ol was the major isomer in CM (66.4%) and CP (61.1%), (-)-α-pinene was the dominant antipode in CL (55.5%) and CM (92.1%). CH contained (-)-citronellal (100%) as the pure enantiomer, while CL and CP have lower proportions (9.0-34.6%), and citronellal is absent in CM. The obtained enantiomeric compositions were compared and discussed with results from eGC using the same enantioselective column. To our knowledge, this work encapsulates the first report that details the EFs of these chiral monoterpenes in Citrus spp. leaf oil.

Risk assessment of Citripestis sagittiferella for the EU.

Following a request from the European Commission, the EFSA Panel on Plant Health performed a risk assessment of Citripestis sagittiferella (Lepidoptera: Pyralidae), the citrus pulp borer, an oligophagous pest reported from South-East Asia and restricted to Citrus spp. The entry risk assessment focused on the citrus fruit pathway. Two scenarios were considered: scenario A0 (current practice) and A2 (additional post-harvest cold treatment). Based on the outputs of the entry model obtained in scenario A0, the median number of founder populations in the EU citrus-growing area is estimated to be slightly less than 10 per year (90%-uncertainty interval between about one entry per 180 years and 1,300 entries per year). The risk of entry and the simulated numbers of founder populations are orders of magnitude lower for scenario A2 compared to scenario A0. The key uncertainties in the entry model include transfer, the cold treatment effectiveness, the disaggregation factor and sorting. The simulated numbers of established populations are only slightly lower than the numbers of founder populations. As the probability of establishment has little impact on the number of established populations, it is not a major source of uncertainty, despite the lack of data on the thermal biology of the pest. The median lag period between establishment and spread is estimated to be slightly more than 1 year (90%-uncertainty interval between about 2months and 33months). After the lag period, the median spread rate by natural means (flying) and due to transport of harvested citrus fruit from orchards to packinghouses is estimated at about 100km/year (90%-uncertainty interval between about 40 and 500km/year). The main sources of uncertainties affecting the spread rate include the extent to which environmental factors could hamper the build-up of the populations and the lack of data on the spread rate at the origin. The median impact of C. sagittiferella in the EU citrus-growing area is estimated at about 10% of infested fruits among the harvested citrus fruits (90%-uncertainty interval between about 2% and 25%). Uncertainties affecting the impact assessment include the susceptibility of different Citrus species and cultivars.

Pangenome-wide analysis of cyclic nucleotide-gated channel (CNGC) gene family in citrus Spp. Revealed their intraspecies diversity and potential roles in abiotic stress tolerance.

Cyclic nucleotide-gated channels (CNGC) gene family has been found to be involved in physiological processes including signaling pathways, environmental stresses, plant growth, and development. This gene family of non-selective cation channels is known to regulate the uptake of calcium and is reported in several plant species. The pangenome-wide studies enable researchers to understand the genetic diversity comprehensively; as a comparative analysis of multiple plant species or member of a species at once helps to better understand the evolutionary relationships and diversity present among them. In the current study, pangenome-wide analysis of the CNGC gene family has been performed on five Citrus species. As a result, a total of 32 genes in Citrus sinensis, 27 genes in Citrus recticulata, 30 genes in Citrus grandis, 31 genes in Atalantia buxfolia, and 30 genes in Poncirus trifoliata were identified. In addition, two unique genes CNGC13 and CNGC14 were identified, which may have potential roles. All the identified CNGC genes were unevenly distributed on 9 chromosomes except P. trifoliata had genes distributed on 7 chromosomes and were classified into four major groups and two sub-groups namely I, II, III, IV-A, and IV-B. Cyclic nucleotide binding (CNB) motif, calmodulin-binding motif (CaMB), and motif for IQ-domain were conserved in Citrus Spp. Intron exon structures of citrus species were not exactly as same as the gene structures of Arabidopsis. The majority of cis-regulatory elements (CREs) were light responsive and others include growth, development, and stress-related indicating potential roles of the CNGC gene family in these functions. Both segmental and tandem duplication were involved in the expansion of the CNGC gene family in Citrus Spp. The miRNAs are involved in the response of CsCNGC genes towards drought stress along with having regulatory association in the expression of these genes. Protein- Protein interaction (PPI) analysis also showed the interaction of CNGC proteins with other CNGCs which suggested their potential role in pathways regulating different biological processes. GO enrichment revealed that CNGC genes were involved in the transport of ions across membranes. Furthermore, tissue-specific expression patterns of leaves sample of C. sinensis were studied under drought stress. Out of 32 genes of C. sinensis 3 genes i.e., CsCNGC1.4, CsCNGC2.1, and CsCNGC4.2 were highly up-regulated, and only CsCNGC4.6 was highly down-regulated. The qRT-PCR analysis also showed that CNGC genes were highly expressed after treatment with drought stress, while gene expression was lower under controlled conditions. This work includes findings based on multiple genomes instead of one, therefore, this will provide more genomic information rather than single genome-based studies. These findings will serve as a basis for further functional insights into the CNGC gene family.

Authentication of Citrus spp. Cold-Pressed Essential Oils by Their Oxygenated Heterocyclic Components.

Citrus essential oils are routinely adulterated because of the lack of regulations or reliable authentication methods. Unfortunately, the relatively simple chemical makeup and the tremendous price variations among Citrus varieties encouraged the interspecies adulteration of citrus oils. In this study, a sensitive UPLC-MS/MS method for the quantitation of 14 coumarins and furanocoumarins is developed and validated. This method was applied to screen the essential oils of 12 different Citrus species. This study, to our knowledge, represents the most comprehensive investigation of coumarin and furanocoumarin profiles across commercial-scale Citrus oils to date. Results show that the lowest amount was detected in calamansi oil. Expressed oil of Italian bergamot showed the highest furanocoumarin content and the highest level of any individual furanocoumarin (bergamottin). Notable differences were observed in the coumarin and furanocoumarin levels among oils of different crop varieties and origins within the same species. Potential correlations were observed between bergapten and xanthotoxin which matches with known biosynthetic pathways. We found patterns in furanocoumarin profiles that line up with known variations among the Citrus ancestral taxa. However, contrary to the literature, we also detected xanthotoxin in sweet orange and members of the mandarin taxon. Using multivariate analysis, we were able to divide the Citrus oils into 5 main groups and correlate them to the coumarin compositions.

Propagation of “Valencia” orange (Citrus x sinensis Osbeck) by minigraft

Demand for citrus (Citrus spp) plants for commercial orchards has increased worldwide due to the need for new plantations, renewal of disease-effected crops, and strict regulation for plant production. To evaluate faster and low-cost propagation alternatives for citrus, “Valencia” orange plants were propagated by using two minigrafting techniques (Cleft and inverted T-budding). Rootstocks were raised from “Cleopatra” mandarin seeds, and scions and buds were isolated from 1-year-old grafted plants. For cleft minigrafts, scions were inserted at 5-7 cm height inside of the decapitated rootstocks and covered with Eppendorf® tubes. For T-budding, buds were inserted at 5-7 cm height under the rootstock cortex cut. Unions were fixed with Parafilm®. Grafted plants were maintained under a shade house (50%) with two daily fog irrigation (2 min each). Treatments were distributed with a completely randomized design. Six weeks after grafting, the percentage of success, the shoot length, and the number of leaves per treatment were registered and analyzed with a T test (α=0.05). Cleft minigraft resulted in a higher success percentage and plants with larger shoots. Cleft minigraft could be considered an alternative for citrus propagation in small and medium size nurseries.

Insecticidal activity of the essential oil of Schinus areira against Rhipibruchus picturatus (F.) (Coleoptera: Bruchinae), and its inhibitory effects on acetylcholinesterase

During the storage of Prosopis alba pods, substantial quantitative and qualitative losses were observed. One of the main factors is the seed beetle Rhipibruchus picturatus. A key strategy to develop new pest control management is the use of essential oils (EOs) due they are efficient, less toxic, and less persistent in the environment compared to synthetic pesticides. In this context, seeds and leaves of Schinus areira L. (Anacardiaceae) EOs and Citrus spp. EO were studied in the present work. In the leaves of S. areira EO, 1-epi-cadinol, sesquiterpenoid alcohol, was the major compound. On the other hand, the main compounds of the EO extracted from S. areira seeds are the monoterpenes sabinene, and α-pinene. Finally, in the Citrus EO, limonene is the principal component. The three EOs obtained exhibited insecticidal activity against R. picturatus, being the first report of the use of EOs against this insect pest. The best insecticidal results were obtained with the leaves of S. areira EO. Moreover, this EO inhibits the acetylcholinesterase enzyme in vitro assays. Molecular docking studies on acetylcholinesterase (AChE) suggest that the main components of the leaves of S, areira EOs, bind to the active site of the enzyme, in good agreement with in vitro competitive inhibition against AChE observed for this EO. The data obtained demonstrate the potential use of Schinus areira EOs in the development of new storage pest control strategies.

Ecotechnology of isoprene, resembles, ph beyond central-dogma to spoil evil-helix of virions or else their genetic materials in a natural gene-editing process of ayurveda

Digitally Ayurveda totally can spoil evil proteins, virions, microbes mere foreign-proteins, unlike multi-cellulars, can easily get denatured with plants acids (pH < 6.5) or with plants alkaloids (pH > 8.0) and Isoprene may in between. This research study found in fisheries and mankind The very well known fact to mankind is that pathogenic or foreign-proteins, namely virus and bacteria can be denatured with mild Ayuyrvedic acids or Alkaloids. Ground-truth microbial counts and digital parameters of ecology can find relations viz. machine learning techniques, of departing hydrophilic viruses, microbes with hydrophobicity of hydrocarbons or else reactive Isoprene.. In earlier studies author found that hydrocarbon Isoprene the smallest unit of essential Authors are running Ayurveda gardens with fascinating plant specieses namely Justasia spp and Citrus plants those are releasing plants acids, Isoprene etc can protect and prevent any viruses with Isoprene instant proofs. May be gene editing of of all evil viruses with Isoprene remains be pre historic and established since Ayurvedic era Modern digital-research of Chromatography, Distillations or digital electronics can find that Isoprene and few others when emitted by plants or algae can prevent viruses and with a fact that oldest prescription of Ayurveda may be the worthiest to the mankind. Also natural gene-editing possible with Ayurveda science since pre-historic era and re-invented. Today Ayurveda science may be as advanced and authentic with perspective to gene editing or gene-therapy. In recent years we find whole world is full panicked with every word-goes starting with viruses, their all kind of mutants etc. However once we take very worthy Isoprene to Terpenoids from plants and Fatty bio-molecules etc. this may be God gifted bio-molecules that prevent and cure virus attack or even its mutants by damaging their genetic traits. Modern Ayurveda says any anomaly in mankind caused by viruses or its mutants can be cured with natural gene-editing plants i.e. Justicia spp, with stated Ayurveda science containing Isoprene, acting gene-editing enzyme, non conventional and non protein bio-molecule by forming isoprene phosphate reversibly, along with all the precursors of desiring genetic-base materials such as Purine and Pyrimidine obtainable from very popular Alkaloid biomolecules namely Vasicine, Vascineone and Quinazoline, respectively sourced from Justacia spp, or else simply fed them with Citrus spp or Switenia mahagony leaves all this containing Isoprene and hence animals fed gets escaped from any kind of virus diseases. All this Ayurvedic plants since pre-historic era and proven true Ultra natural all the mentioned biomolecules also obtainable at their respective temperature of vapour point (vp) from individual plant extracts. Whereas examples are given with aquatic data of fisheries environments.

Fertility Levels of Soils under Selected Tree Vegetations for Efficient Agro-Forestry in Imo State, Nigeria

In many parts of Nigeria, large areas of lands are dominated by tree crop vegetations for timber production and for fruits with land users not knowing the fertility status of soils in these vegetations. Continual evaluation of soil properties of these tree vegetations has become pertinent for agricultural sustainability. This study therefore was carried out to evaluate the fertility levels of soils under selected tree vegetations at National Horticultural Research Institute Okigwe, Imo State, Nigeria. Five tree vegetations that were over 20 years of establishment were selected namely: oil bean (Pentaclethra macrophylla Benth), African breadfruit (Treculia africana), mango (Mangnifera indica), Ogbonu (Irvingia gabonensis) and orange (citrus spp). In each of these tree vegetations, four soil samples were collected at uniform depths (0 – 20, 20 – 40 and 40 – 60 cm) at different locations using soil auger. The samples were analyzed using standard laboratory procedures. Data collected were statistically analyzed using analysis of variance. Results obtained showed that despite the ages of these vegetations, the soils were acidic, low in macronutrient and basic cation concentrations when compared to FAO standard. The highest exchangeable bases and organic matter (1.78%) was recorded on bread fruit vegetation. Therefore, there is need to increase the fertility status of these soils in these tree crop vegetations by adopting measures that will boost organic matter content of the soil irrespective of the duration of the vegetation and this will help in agro forestry and alley cropping.

Diaphorina communis: Molecular identification, development on Citrus reticulata, and acquisition and transmission of ‘Candidatus Liberibacter asiaticus’

AbstractThe black curry leaf psyllid, Diaphorina communis, is a host of the citrus pathogen, ‘Candidatus Liberibacter asiaticus’ (‘CLas’). However, there is a paucity of information on its biology; hence, this study was conducted to evaluate survival and development on citrus, in this instance mandarin (Citrus reticulata) and curry leaf (Bergera koenigii), and transmission of ‘CLas’. Given its similarity with the Asian citrus psyllid (Diaphorina citri), sequences of the COI and 16S genes were examined to see if they could distinguish molecularly between nymphs of these two species. Field and laboratory experiments showed that D. communis nymphs transferred to mandarin branches failed to survive. Adults could survive on flush growth of ‘CLas’‐infected mandarin trees; however, little oviposition took place, and the single resulting nymph did not survive to the second instar. These observations suggest that D. communis does not develop, or rarely develops on mandarin and possibly other Citrus spp. Curry leaf appears to be its preferred host, and complete development can take place, possibly exclusively, on this species. Studies on acquisition of ‘CLas’ by D. communis and possible transmission assessed in 2014 and 2015 using greenhouse‐grown curry leaf and mandarin seedlings with naturally infected mandarin stumps as a source of ‘CLas’ indicated a low acquisition rate of ‘CLas’. In addition, although D. communis can acquire ‘CLas’, it either cannot transmit it or transmission is limited, and the pathogen may not multiply within the insect. Phylogenetic analyses indicate that differences in COI and 16S regions may prove useful for differentiating between early instar D. communis and D. citri nymphs when fifth instar nymphs and adults are not present on host plants.

In Vitro Evaluation of Acute Toxicity of Five Citrus spp. Essential Oils towards the Parasitic Mite Varroa destructor.

Varroa destructor is the most important ectoparasitic mite of honey bees that has a negative impact on bee health and honey production. The control programs are mainly based on the use of synthetic acaricides that are often administered indiscriminately. All this has led to drug resistance that now represent a great concern for honey bee farming. The research for alternative products/methods for mites’ control is now mandatory. The aim of this study was to test whether Citrus spp. essential oils could diminish the growth of the V. destructor mite. In Calabria (southern Italy), plants of the Citrus genus are very common and grow both spontaneously and cultured. The essential oils used in this study were extracted from bergamot (Citrus bergamia), grapefruit (Citrus paradisi), lemon (Citrus limon), orange (Citrus sinensis), and mandarin (Citrus reticulata) by hydrodistillation. Every EO was in vitro tested against V. destructor. Each experimental replicate was performed using 35 viable adult female mites (5 for each EO) collected the same day from the same apiary and included negative controls (5 individuals exposed to acetone only) and positive controls (5 individuals exposed to Amitraz diluted in acetone). The essential oils (Eos) were diluted (0.5 mg/mL, 1 mg/mL, and 2 mg/mL) in HPLC grade acetone to obtain the working solution to be tested (50 µL/tube). Mite mortality was manually assessed after 1 h exposure under controlled conditions. The essential oils that showed the best effectiveness at 0.5 mg/mL were bergamot, which neutralized (dead + inactivated) 80% (p ≤ 0.001) of the parasites; grapefruit, which neutralized 70% (p ≤ 0.001); and lemon, which neutralized 69% of them. Interestingly, the positive control (Amitraz) at the same concentration neutralized 60% of the parasites. These results demonstrate that Calabrian bergamot, grapefruit, and lemon Eos consistently reduced V. destructor viability and open the possibility for their utilization to control this parasite in honey bee farming.

Different Phytohormonal Responses on Satsuma Mandarin (Citrus unshiu) Leaves Infected with Host-Compatible or Host-Incompatible Elsinoë fawcettii.

Citrus scab, caused by the fungal pathogen Elsinoë fawcettii, is one of the most important fungal diseases affecting Citrus spp. Citrus scab affects young tissues, including the leaves, twigs, and fruits, and produces severe fruit blemishes that reduce the market value of fresh fruits. To study the molecular responses of satsuma mandarin (C. unshiu) to E. fawcettii, plant hormone-related gene expression was analyzed in response to host-compatible (SM16-1) and host-incompatible (DAR70024) isolates. In the early phase of infection by E. fawcettii, jasmonic acid- and salicylic acid-related gene expression was induced in response to infection with the compatible isolate. However, as symptoms advanced during the late phase of the infection, the jasmonic acid- and salicylic acid-related gene expression was downregulated. The gene expression patterns were compared between compatible and incompatible interactions. As scabs were accompanied by altered tissue growth surrounding the infection site, we conducted gibberellic acid- and abscisic acid-related gene expression analysis and assessed the content of these acids during scab symptom development. Our results showed that gibberellic and abscisic acid-related gene expression and hormonal changes were reduced and induced in response to the infection, respectively. Accordingly, we propose that jasmonic and salicylic acids play a role in the early response to citrus scab, whereas gibberellic and abscisic acids participate in symptom development.

Stress-inducible Arabidopsis thaliana RD29A promoter constitutively drives Citrus sinensis APETALA1 and LEAFY expression and precocious flowering in transgenic Citrus spp.

Transgenic 'Duncan' grapefruit (Citrus paradisi Macf.) and 'Valencia' sweet orange (Citrus sinensis [L.] Osbeck) plants ectopically expressing C. sinensis (cv. Washington navel orange) APETALA1 (CsAP1) or LEAFY (CsLFY) genes under control of the Arabidopsis thaliana stress-inducible promoter AtRD29A flowered under non-inductive (warm temperature, well-watered) greenhouse conditions, whereas their wild-type (WT) counterparts did not. The transgenic plants that flowered exhibited no altered morphological features, except the lack of thorns characteristic of juvenile WT plants. The most precocious T0 line, 'Duncan' grapefruit (Dun134-3) expressing the CsAP1 gene, flowered and fruited when it was 4.5years old and the T1 siblings from this line flowered and fruited when they were just over 18months old. In contrast, T1 seedlings from three lines of 'Duncan' grapefruit expressing the CsLFY gene flowered within 3months after germination, but were unable to support fruit development. Transcript levels of corresponding transgenes in leaves were not correlated with earliness of flowering. To further study the activity of AtRD29A, leaves from three 'Carrizo' citrange (C. sinensis×Poncirus trifoliata) rootstock seedlings transformed with the green fluorescent protein (GFP) gene under regulation of the AtRD29A promoter were subjected to drought stress or well-watered conditions. Expression of GFP was not stress-dependent, consistent with the observation of flowering of CsAP1 and CsLFY transgenic plants under non-inductive conditions. Taken together, the results suggest that AtRD29A is constitutively expressed in a citrus background. Despite the loss of control over flowering time, transgenic citrus lines ectopically expressing C. sinensis AP1 or LFY genes under control of the A. thaliana RD29A promoter exhibit precocious flowering, fruit development and viable transgenic seed formation. These transformed lines can be useful tools to reduce the time between generations to accelerate breeding.

Prevalence and Assessment of Disease Incidence and Severity in Citrus Orchards of Sub Zoba Hamelmalo

Citrus (Citrus spp. L.) production in Eritrea covers over 2409 ha of the land but the average potential of production is 91 q/ha to 150 -170 q/ha. This low yield might be due to lack of knowledge on management practices, adverse environmental factors and different diseases caused by various pathogens. Moreover, there is no proper recorded data on the identification of diseases on citrus and its intensity, hence, this survey: to identify the prevailed diseases; assessment of disease incidence, severity and calculate the ‘Area Under Disease Progress Curve’ (AUDPC). A survey was carried out in three orchards in each five citrus producing villages (Fredarb, Tsebabo, Hamelmalo, Wazntetand Genfelom) from sub-zoba Hamelmalo. The fungal diseases found on citrus were brown spot, sooty mold, gummosis, black spot, scab and melanose; the bacterial infection was canker; and viral diseases were leprosis and cholorotic dwarf. The highest percentage of disease incidence was recorded Fredarb with 77.16% and the lowest was found in Genfelom with 47.29 % in the same month. The highest percentage of diseases severity was found in Hamelmalo with 40.02%. On the other hand, the least percentage of disease severity was found in Genfelomwith 25.04%. The influence of epidemiological factors showed that they could be some of the reasons to develop and spread the mean disease incidence (65.6%) in February, 2018. The AUDPC was recorded highest (2829) in the orchard 3 of Hamelmalo, and lowest (1152) in orchard 3 of Tsebabo. A decreasing trend of temporal disease data from the first month to the third month was estimated in the orchard 2 and orchard 3 of Fredarb, orchard 2 of Genfelom, orchard 1 of Hamelmalo, all orchards of Tsebabo and in both orchard1 and 3 of Wazntet villages.