Essential oils of citrus fruit stimulate oviposition in the Mediterranean fruit fly Ceratitis capitata (Diptera: Tephritidae)

Female Mediterranean fruit flies (medfly) Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) perceive both qualitative and quantitative aspects of citrus fruit chemistry. However, the behavioural and biological adjustments of this response remain largely unknown. In the present study, the ovipositional responses of gravid female medflies to essential oils (i.e. the most critical resistance factor to medfly infestation) of various citrus fruits are investigated. In dual‐choice (treatment versus distilled water control) experiments, females lay significantly more eggs into pre‐punctured hollow oviposition hemispheres (domes) provided with 1 µL of citrus peel oil from sweet orange, satsuma mandarin, bitter orange, grapefruit and lemon compared with odourless domes. No‐choice tests show a weak effect of lemon essential oils in stimulating oviposition. The female ovipositional response to sweet orange oil (the most active in eliciting oviposition) is dose‐dependent. Additionally, limonene, the most abundant chemical in all citrus oils, stimulates oviposition, whereas linalool, a representative compound of immature citrus fruit associated with high toxicity against immature stages of fruit flies, has a significant deterrent effect. In further no‐choice tests, females lay approximately 23% fewer eggs in limonene (93%) (amount found in orange oil) and 60% fewer eggs in limonene 93% plus linalool 3% (approximately 10‐fold the amount found in orange oil) mixtures, relative to sweet orange oil. The results suggest that the limonene content accounts largely (but not completely) for the ovipositional responses observed in sweet orange oil, whereas high linalool proportions are capable of significantly masking and/or disrupting its stimulatory effects in citrus oils. The importance and practical implications of these findings with respect to understanding how citrus fruit chemistry influences the ovipositional responses of medfly is discussed.     

Are citrus species favorable hosts for the Mediterranean fruit fly? A demographic perspective

We studied, under laboratory conditions, demographic parameters of adult Mediterranean fruit flies, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) (medfly), obtained from three sweet orange varieties, lemon, and bitter oranges. These data were combined with immature developmental rates and survival on the same hosts to estimate host‐specific population parameters. Pairs of newly emerged adults from each citrus variety were held individually in transparent plastic cages, and females were allowed to oviposit in either red domes (artificial, pre‐punctured plastic oviposition devices), or intact, whole citrus fruits. We found strong effects of larval host (citrus fruits) on adult longevity and fecundity. In all five citrus varieties, females did not manage to deposit eggs into fruit pulp. The proportion of eggs laid in either the flavedo or albedo area of the fruit peel differed depending on the citrus variety. In all cases except bitter oranges, females oviposited fewer eggs in citrus fruits than in the artificial oviposition substrates, suggesting that most citrus fruits cause a significant reduction in the reproductive potential of medflies. Negative correlations were found between fecundity and (a) the density of oil glands, and (b) the amount of essential oils in the flavedo area of citrus fruits. There was no correlation between fecundity and other fruit physical characteristics, such as resistance of fruit peel to pressure and thickness of the flavedo. Apparently, resistance of citrus fruits to medfly infestation is directly related to citrus essential oils. The intrinsic rate of increase (r) was higher in bitter oranges than in the three sweet orange varieties tested. A negative r was estimated for flies that developed and oviposited in lemons, indicating a tendency for population decrease in this host. The suitability of citrus fruits for medfly development and the practical implications of our findings for management of medflies in citrus orchards are discussed.     

Chemical composition and antimicrobial activity of Citrus essences on honeybee bacterial pathogen <Emphasis Type="Italic">Paenibacillus larvae</Emphasis>, the causal agent of American foulbrood

Antimicrobial properties and chemical composition of four citrus fruit essential oils to control Paenibacillus larvae, the causal agent of American foulbrood disease (AFB) were determined. This honeybee larvae disease occurs throughout the world and is found in many beekeeping areas of Argentina. Citrus fruit essential oils tested were those from grapefruit (Citrus paradisi), sweet orange (Citrus sinensis), mandarin (Citrus nobilis) and lemon (Citrus limon). The components of the essential oils were identified by SPME-GC/MS analysis. The antimicrobial activity of the oils against P. larvae were determined by the broth microdilution method. Two way ANOVA tests for minimum inhibitory concentrations (MICs) data and minimal bactericide concentrations (MBCs) data, indicated significant differences between the strains and the oils tested. The antimicrobial assays showed that the oil of C. paradisi inhibited the bacterial strains at the lowest concentrations tested, MICs and MBCs averages of 385.0 mg/l and 770.0 mg/l, respectively. This property could be attributed to the kind and percentage of the volatile components of the oil, like limonene (69.9%) and myrcene (9.6%). The use of essential oils or their specific volatile components individually against pests related to food provision may represent an alternative scope for the control of this serious disease because it does not leave toxic chemical residues in honey nor in its by products.     

Survival and development of immature stages of the Mediterranean fruit fly (Diptera: Tephritidae) in citrus fruit

We studied, under laboratory conditions, the performance of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), immature stages in intact whole fruit of three sweet orange varieties, lemon, and bitter oranges. Both citrus variety and fruit part (flavedo, albedo, and pulp) had strong effects on larval performance, smaller effects on pupae, and no effects on eggs. Fruit peel was the most critical parameter for larval development and survival, drastically affecting larval survival (inducing very high mortality rates). Among fruit regions, survival of larvae placed in flavedo was zero for all varieties tested except for bitter orange (22.5% survival), whereas survival in albedo was very low (9.8-17.4%) for all varieties except for bitter orange (76%). Survival of pupae obtained from larvae placed in the above-mentioned fruit regions was high for all varieties tested (81.1-90.7%). Fruit pulp of all citrus fruit tested was favorable for larval development. The highest survival was observed on bitter oranges, but the shortest developmental times and heaviest pupae were obtained from orange cultivars. Pulp chemical properties, such as soluble solid contents, acidity, and pH had rather small effects on larval and pupal survival and developmental time (except for juice pH on larvae developmental duration), but they had significant effects on pupal weight.     

Biochemical characterization of blood orange,sweet orange,lemon, bergamot and bitter orange

This paper reports on the composition of aroma compounds and fatty acids and some physico-chemical parameters (juice percentage, acidity and total sugars) in five varieties of citrus: blood orange, sweet orange, lemon, bergamot and bitter orange. Volatile compounds and methyl esters have been analyzed by gas chromatography. Limonene is the most abundant compound of monoterpene hydrocarbons for all of the examined juices. Eighteen fatty acids have been identified in the studied citrus juices, their quantification points out that unsaturated acids predominate over the saturated ones. Mean concentration of fatty acids varies from 311.8 mg/l in blood orange juice to 678 mg/l in bitter orange juice.     

Response of Ceratitis capitata to citrus chemicals under semi-natural conditions

Responses of Mediterranean fruit fly Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) adults to chemicals from citrus fruits were quantified in choice tests conducted in large field cages housing naturally planted orange trees, on the Greek island of Chios. Both sexes responded strongly to chemicals released from artificial cuts made in the pulp of peeled oranges and also to natural or commercial orange juice applied to the surface of yellow 7.0 cm diameter spheres. Males also responded strongly to chemicals released from cuts made in the oily region of the orange peel, or flavedo and less to sour orange and lemon. In contrast, females did not respond to flavedo chemicals. Male response to peel chemicals occurred throughout the day and increased as the number of cuts per fruit increased from 2 to 8. Contact of male mouthparts with sap from cuts, and mating attempts between males on or near the cuts were frequently observed. The males also responded to commercial essential orange oils applied to yellow spheres, but less to essential mandarin oils. The role of citrus chemicals in host finding behaviour of C. capitata and their potential use for the development of effective traps for monitoring and controlling the fly are discussed. The experimental method followed in this study can be used as a standard technique for evaluation of the quality of flies to be used in sterile insect technique programmes.     

Chemical Studies on the Essential Oils of Foeniculum vulgare

Twenty seven chemical constituents of oils from sweet leaves, flowers and fruits of Foeniculum vulgare Mill. are examined by GC and GC-MS with both different chromatographic columns. They are 1,1-diethoxyethane, α-thujene, α-pinene, camphene, sabinene, β-pinene, myrcene, α- phellandrene, p-cymene, limonene, cineole, γ-terpinene, fenchone, camphor, terpinen-4-ol, α-terpineol, estragole, verbenone, fenchol acetate, carveol, trans-fenchol acetate, carvone, anethole, anisaldehyde, trans-anethole, methoxyphenyl acetone and benzoic acid, 4-methoxy-, othylester. The limonene is 57.8% in the essential oil from leaves, 34.2% from flowers, 13.1% from fruits, The trans-anethole is 21.8% in the essential oil from leaves, 41.2% from flowers, 63.4% from fruits.     

中国悬钩子属植物的利用价值概述

主要报道中国悬钩子属植物作为果树种质资源和药用植物的利用价值及果实色素和香味成分的利用潜力。经过十余年的调查１引种栽培和观测评价,发现一些种类可以作为野生小果类果树直接利用,其中２３种４变种是悬钩子类果树选育种的优良种质。据文献记载和民间调查发现。４５种４变种悬钩子植物可以作为中草药治疗多种疾病。对灰白毛莓、高梁泡、蓬、掌叶复盆子和黑莓果实色素的研究结果表明：悬钩子果实色素以醇提法为佳,水提法效果     

Isotope Ratio by HRGC-MS of Citrus junos Tanaka (Yuzu) Essential Oils: m/z 137/136 of Terpene Hydrocarbons

The isotope ratios of monoterpene hydrocarbons in Citrus junos Tanaka (yuzu) essential oils from different origins were determined by ordinary high-resolution gas chromatography-mass spectrometry (HRGC-MS). Both intensities of the molecular mass peaks (m/z 136) and of the isotope peaks (m/z 137) of monoterpene hydrocarbons were measured by single-ion monitoring with an MS analysis. The isotope ratios (m/z 137/136) of the ten monoterpene hydrocarbons commonly contained in citrus essential oils, α-pinene, β-pinene, sabinene, myrcene, α-phellandrene, α-terpinene, limonene, γ-terpinene, β-phellandrene and terpinolene, were determined in yuzu samples of the highest commercial quality from 42 different production districts. Statistical treatment of these data by the t-test and sign test revealed significant differences of the isotope effects in each yuzu sample. It is suggested that this technique will be applicable for evaluating the quality, genuineness and origin of citrus fruits and their products. The isotope fingerprints were also demonstrated in several citrus fruits other than the yuzu samples.     

Terpene down-regulation in orange reveals the role of fruit aromas in mediating interactions with insect herbivores and pathogens

Plants use volatile terpene compounds as odor cues for communicating with the environment. Fleshy fruits are particularly rich in volatiles that deter herbivores and attract seed dispersal agents. We have investigated how terpenes in citrus fruit peels affect the interaction between the plant, insects, and microorganisms. Because limonene represents up to 97% of the total volatiles in orange (Citrus sinensis) fruit peel, we chose to down-regulate the expression of a limonene synthase gene in orange plants by introducing an antisense construct of this gene. Transgenic fruits showed reduced accumulation of limonene in the peel. When these fruits were challenged with either the fungus Penicillium digitatum or with the bacterium Xanthomonas citri subsp. citri, they showed marked resistance against these pathogens that were unable to infect the peel tissues. Moreover, males of the citrus pest medfly (Ceratitis capitata) were less attracted to low limonene-expressing fruits than to control fruits. These results indicate that limonene accumulation in the peel of citrus fruit appears to be involved in the successful trophic interaction between fruits, insects, and microorganisms. Terpene down-regulation might be a strategy to generate broad-spectrum resistance against pests and pathogens in fleshy fruits from economically important crops. In addition, terpene engineering may be important for studying the basic ecological interactions between fruits, herbivores, and pathogens.     

Susceptibility and Resistance of Citrus Genotypes to Alternaria alternata pv. citri

A survey of citrus cultivars in Israel in orchards where Alternaria brown spot was common on Minneola tangelos (mandarin × grapefruit), revealed the occurrence of the disease as typical foliar and fruit lesions on Dancy and Ellendale (mandarins), on Murcott tangor (mandarin × sweet orange), on Nova and Idith (mandarin hybrids), on Calamondin, and on Sunrise and Redblush (grapefruit). Isolates of Alternaria alternata from each of these hosts were proven to be pathogenic to Minneola tangelo.
The host range of A. alternata pv. citri from Israel was assayed by inoculating leaves of diverse citrus genotypes. Several mandarins and their hybrids (Dancy, Kara, King, Wilking, Satsuma, Minneola, Orlando, Mikhal, Idith, Nova, Page, Murcott), grapefruit (Marsh seedless), grapefruit × pummelo (Oroblanco), sweet orange (Shamouti, Valencia, Washington navel) Calamondin, and Volkamer citrus were susceptible. Several mandarins and their hybrids (Clementine, Avana, Yafit, Ortanique), Cleopatra, one sweet orange cultivar (Newhall), pummelo (Chandler), lemon (Eureka), Rough lemon, Rangpur lime, sweet lime, citron, limequat, sour orange, Troyer citrange and Alemow were resistant.     

Isotope ratio analysis by HRGC-MS of monoterpene hydrocarbons from citrus essential oils

The isotope ratio of monoterpene hydrocarbons in citrus essential oils of different origins was measured by ordinary high-resolution gas chromatography-mass spectrometry (HRGC-MS). The isotope ratio (Ir) was determined by the ratio of the isotope peak intensity (m/z 137) to the molecular mass peak intensity (m/z 136) of the monoterpene hydrocarbons. The accuracy of Ir was examined by measuring monoterpene hydrocarbon standards and 13C-labeled compounds. The isotope fingerprints based on the values of monoterpene hydrocarbons from lemon, lime and yuzu essential oils were determined. These citrus essential oils were also discriminated by a principal component analysis of their Ir data. The characteristic vectors showed that alpha-terpinene, beta-pinene and beta-phellandrene were important components for distinguishing between the citrus species. It is suggested that this technique will be applicable to evaluate the quality, genuineness and origin of citrus fruits and their products.     

Toxicity of some terpenoids of essential oils of Xylopia aethiopica from Cameroon against Sitophilus zeamais Motschulsky

Abstract:  The acute toxicity of essential oils from the whole fruit (EF) or from the fibres of the fruit (FF) of the local aromatic plants Xylopia aethiopica Dunal (Annonaceae) collected in north Cameroon was evaluated on Sitophilus zeamais adults. A concentration of 1 ml of essential oil per 100 g of maize seeds was tested to determine weevil mortality after 24 h of exposure. Under these conditions, the essential oil derived from both EF and FF of X. aethiopica led to 100% mortality. In a second step, proportions of active compounds present in the oil of both EF and FF of X. aethiopica were quantified. The toxicity of the four main compounds was tested against S. zeamais : α -pinene, β -pinene, Δ-3-carene and terpinen-4-ol according to their proportion in the essential oil of the concerned plant part. β -pinene and terpinen-4-ol were responsible for 50% of the mortality at the proportion found in EF and FF essential oils respectively. When mixed, a synergic effect of the compounds was observed that restored the mortality percentage observed for the crude oil. It appears that X. aethiopica essential oil could be a potential source of natural and low-cost insecticide to control storage pests.     

Decreased Immunoreactivity of Hepatitis E Virus Antigen Following Treatment with Sakhalin Spruce (Picea glehnii) Essential Oil

The hepatitis E virus (HEV) causes a common infectious disease that infects pigs, wild boars, deer, and humans. In most cases, humans are infected by eating raw meat. Some essential oils have been reported to exhibit antiviral activities. In this study, in order to investigate the anti-HEV properties of essential oils, the immunoreactivities of HEV antigen proteins against the relevant antibodies were analyzed after the HEV antigens underwent treatment with various essential oils. The essential oils extracted from the tea tree, which was previously reported to exhibit antiviral activity, lavender, and lemon had strongly reduced activity. We found that treatment with the essential oil prepared from Sakhalin spruce was associated with the strongest reduction in immunoreactivity of HEV antigen protein(s) among the tested substances. The main volatile constituents of Sakhalin spruce essential oil were found to be bornyl acetate (32.30 %), α-pinene (16.66 %), camphene (11.14 %), camphor (5.52 %), β-phellandrene (9.09 %), borneol (4.77 %), and limonene (4.57 %). The anti-HEV properties of the various components of the essential oils were examined: treatment with bornyl acetate, the main component of Sakhalin spruce oil, α-pinene, the main component of tea tree oil, and limonene, the main component of lemon oil, resulted in a strong reduction in HEV antigen immunoreactivity. These results indicate that each main component of the essential oils plays an important role in the reduction of the immunoreactivity of HEV antigen protein(s); they also suggest that Sakhalin spruce essential oil exhibits anti-HEV activity. In a formulation with the potential to eliminate the infectivity of HEV in foodborne infections, this essential oil can be applied as an inactivating agent for meat processing and cooking utensils, such as knives and chopping boards.     

Citrus Leprosis and its Status in Florida and Texas: Past and Present

According to published reports from 1906 to 1968, leprosis nearly destroyed the Florida citrus industry prior to 1925. This was supported with photographs showing typical leprosis symptoms on citrus leaves, fruit, and twigs. Support for the past occurrence of citrus leprosis in Florida includes: (1) presence of twig lesions in affected orange blocks in addition to lesions on fruits and leaves and corresponding absence of similar lesions on grapefruit; (2) yield reduction and die-back on infected trees; and (3) spread of the disease between 1906 and 1925. Transmission electron microscopy (TEM) examination of tissue samples from leprosis-like injuries to orange and grapefruit leaves from Florida in 1997, and fruits from grapefruit and sweet orange varieties from Texas in 1999 and 2000 did not contain leprosis-like viral particles or viroplasm inclusions. In contrast, leprosis viroplasm inclusions were readily identified by TEM within green non-senescent tissues surrounding leprosis lesions in two of every three orange leaf samples and half of the fruit samples obtained from Piracicaba, Brazil. Symptoms of leprosis were not seen in any of the 24,555 orange trees examined across Florida during 2001 and 2002. The authors conclude that citrus leprosis no longer exists in Florida nor occurs in Texas citrus based on: (1) lack of leprosis symptoms on leaves, fruit, and twigs of sweet orange citrus varieties surveyed in Florida: (2) failure to find virus particles or viroplasm inclusion bodies in suspect samples from both Florida and Texas examined by TEM; (3) absence of documented reports by others on the presence of characteristic leprosis symptoms in Florida; (4) lack of its documented occurrence in dooryard trees or abandoned or minimal pesticide citrus orchard sites in Florida. In view of the serious threat to citrus in the U.S., every effort must be taken to quarantine the importation of both citrus and woody ornamental plants that serve as hosts for Brevipalpus phoenicis (Geijskes), B. californicus (Banks), and B. obovatus Donnadieu (Acari: Tenuipalpidae) from countries where citrus leprosis occurs.     

Evaluation of three essential oils as potential sources of botanical fungicides

In previous study, thirty essential oils were evaluated in vitro against two citrus pathogens namely Penicillium italicum Wehmer and Penicillium digitatum Sacc. Essential oils of Cinnamomum zeylanicum, Cinnamomum verum and Eugenia caryophyllus were selected because of their high inhibitory activities against both pathogens. The present study was undertaken to evaluate the in vivo activity of these essential oils. Fresh orange fruits were wounded and treated with different concentrations of essential oil (0.5, 1, and 5%) before being infected at the wound site with conidia suspensions of the tested pathogens. When applied at 5%, essential oils tested controlled totally the infections. Among the three essential oils tested, C. zeylanicum seems particularly interesting because of its high protection activity at 1% compare to the others. It reduced the disease incidence from 40 to 70% and the disease severity from 65 to 82%. Moreover no visible damage burn induced on the orange cuticle or skin was observed up to 5% of essential oil. These results strengthen the potential use of essential oils in postharvest disease management of citrus fruit as alternative to chemical fungicides.     

Essential oil composition of four Lomatium Raf. species and their chemotaxonomy

The composition of the essential oils of Lomatium dasycarpum ssp. dasycarpum, Lomatium lucidum, Lomatium macrocarpum var. macrocarpum and Lomatium utriculatum is described. Identification of components was determined from their GC, GC/MS data and many were confirmed by coinjections with authentic samples. Several components were isolated by liquid and gas chromatographic techniques and their structures confirmed from their ¹H and ¹³C NMR spectral data. 2-Methyl and 3-methylbutanoates were the major components of L. dasycarpum fruits as well as stems and leaves oils. β-Phellandrene/limonene, decanal, dodecanal, bornyl acetate, germacrene D, α-humulene and bicyclogermacrene were the major components of the corresponding L. lucidum oils. α-Pinene and β-pinene were the major components of the fruit oil of L. macrocarpum. Its stem and leaf oil was rich in peucenin 7-methyl ether, β-caryophyllene, (Z)-3-hexenol, palmitic acid, linoleic acid and (E)-2-hexenal. Sabinene, (Z)-ligustilide, terpinen-4-ol, β-phellandrene/limonene, β-caryophyllene, myrcene, α-pinene and β-pinene were the major compounds in L. utriculatum fruit oil, while its stem and leaf oil was rich in (Z)-ligustilide, palmitic acid, terpinen-4-ol, linoleic acid and germacrene D. (Z)-Falcarinol was a major component of all the four root oils.     

Current Distribution of Huanglongbing (citrus greening disease) in India as Diagnosed by Real‐Time PCR

The widespread occurrence of Huanglongbing (HLB) was recorded in sixteen citrus growing states of India using the real‐time quantitative PCR and the derived threshold cycle (Ct) value. All the commercially important citrus varieties of mandarin, sweet orange, lime and lemon, pummelo and Satkara were infected with ‘Candidatus Liberibacter asiaticus’, the bacterium associated with HLB. Ct values positive for HLB were found in all the states except Arunachal Pradesh. The primer–probe combination HLBas‐HLBr‐HLBp was found specific to Ca. L. asiaticus and do not exhibit any cross‐reactivity with other pathogenic residents of citrus.     

Brown spot disease of citrus caused by Phaeoisariopsis sp.

Brown spot disease of Citrus spp. was shown to be caused by Phaeoisariopsis sp. It severely affects all varieties of sweet orange, tangerine, grapefruit, lime and rough lemon, smooth lemon being relatively resistant. Fruits and leaves are much more susceptible than stems on which symptoms are rare. On the young fruit circular, slightly sunken, brown necrotic lesions are often associated with a surrounding ring of raised epicarp, giving the fruit a blistered appearance. Lesions on older fruits are usually flat and brown and surrounded by yellow haloes. Premature abscission, especially of young fruits, is common. Leaf symptoms start as greenish yellow patches and a fully formed leaf spot consists of light brown or greyish centre which is surrounded by a dark brown margin bordered by a yellow halo. Generalised foliar chlorosis, caused by coalescence of several lesions, culminates in premature defoliation. During wet weather, centres of both fruit and foliar lesions sporulate and become black. Stem lesions, dark brown and mostly occurring as extensions of petiole lesions, may coalesce causing stem die-back or resulting in the formation of corky internodal lesions. In artificial culture, the fungus sporulated only on media containing an extract of citrus leaf or fruit peel. The characteristics of the fungus mostly based on examination of structures formed on naturally infected parts of the plant, are described. This is probably the first report of a Phaeoisariopsis sp. on citrus.     

The influence of the composition of essential lemon oils on their antioxidant properties and the stability of the components

The antioxidant properties of various essential oils of lemon (Citrus limon L.) were studied by capillary gas liquid chromatography and compared with those of individual limonene and citral and their mixture in model systems. Some differences in resistance towards oxidation of the major components of lemon oils were ascertained and the synergetic effects in the antioxidant activity of the components and their stability were found.