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PubMed2002

[Inhibitory effect of flavones from Ageratum conyzoides on the major pathogens in citrus orchard].

Inter-cropping with Ageratum conyzoides may effectively control major pathogens in citrus orchard. The research showed that flavones produced by and released from A. conyzoides could inhibit the major fungal pathogens, such as Elsimoe fawcetti Bit. Et Jenk, Collectrichum gloeosporimdes Penz, Oidium tingitaninum Carter, Capondium citri Berk et Desm in citrus orchard. 10 flavones, including one glycoside, from A. conyzoides plant were isolated and identified. Most of them could gradually degraded in soil and only 3 flavones could be accumulated and last a long time. Just these 3 flavones could obviously possess inhibitory effect on fungal pathogens in citrus orchard. The inhibitory effect of the 3 flavones was stronger, not only than those of other allelochemicals produced by and released from A. conyzoides, but also than that of Carbenzin, a commercial fungicide. Therefore, the flavones produced by and released from A. conyzoides played an important role in pathogens control in citrus orchard.

Ageratum↗
PubMed2004

Impact of genetically modified Enterobacter cloacae on indigenous endophytic community of Citrus sinensis seedlings.

Enterobacter cloacae (strain PR2/7), a genetically modified endophyte (GME) in citrus plants, carrying different plasmids (pEC3.0/18, pCelE, pEglA and pGFP), was inoculated into Citrus sinensis seedlings under greenhouse conditions. The impact of this on the indigenous bacterial endophytic community was studied by analyses of 2 different morphologic groups. The germination rates of inoculated seeds were evaluated in greenhouse, and plasmid stability under in vitro conditions. Results demonstrated a great and diverse endophytic community inside plants, and specialization in tissue colonization by some bacterial groups, in different treatments. Shifts in seed germination rate were observed among treatments: in general, the PR2/7 harboring pEglA bacterial clone significantly reduced seed germination, compared to the PR2/7 harboring pEC3.0/18 clone. This suggests that the presence of the pEglA plasmid changes bacteria-seed interactions. The endophytic community of citrus seedlings changed according to treatment. In seedlings treated with the PR2/7 with pEglA clone, the population of group II decreased significantly, within the context of the total endophytic community. These results indicate that the application of GMEs induces shifts in the endophytic bacterial community of citrus seedlings.

Bacteria↗
PubMed2006

[Study on a bacterial strain Bt8 for biocontrol against citrus bacterial canker].

Citrus bacterial canker is an important disease of Citrus species in China. The disease severely occurs especially in the coastal area. Integrated control system has been used for the control of the disease, in which chemotherapy plays an important role at present. The chemotherapy-dominant control system brought many problems to the environment, such as chemical residua in the products and induction of resistance to fungicide(s) by the pathogen. To solve these problems, an intensive study on biocontrol of citrus bacterial canker is needed. Isolations and characterizations of biocontrol agents are the basis for biocontrol of the disease. A bacterial strain Bt8 with strong inhibiting ability against Xanthomonas axonopodis pv. citri (Hasse) Vauterin, was isolated from citrus orchard soil in Nanning, China. The isolated bacterial strain was identified and characterized as Acinetobacter baumannii Bouvet et Grimont on the base of its morphology and 16S rDNA sequence analysis as well as physiological and biochemical characters. The inhibiting activity of the bacterium suspension against the pathogen was significantly influenced by environmental factors, such as temperatures, pHs and media. At temperatures of 18 degrees C to 33 degrees C, both the inhibiting activity of the bacterium suspension and the biomass of the bacterium increased with the increases of temperatures, suggesting that the influence of temperature on inhibiting activity of the bacterium suspension was in dependence on the bacterial biomass. In NA liquid medium of pH 10, the bacterium suspension showed the highest inhibiting activity against Xanthomonas axonopodis pv. citri, which was not in dependence on biomass of the bacterium. The bacterium suspension provided 55.2% inhibition against bacterial canker under greenhouse conditions. The results showed that Acinetobacter baumannii has potential as biocontrol agent against bacterial canker disease. Acinetobacter baumannii was reported as the pathogens infecting human and animals. The present study enriched the understanding on biological diversity in Acinetobacter baumannii to sciences. This is the first report on the isolation of Acinetobacter baumannii with strong inhibiting ability against plant pathogen.

Acinetobacter baumannii↗
PubMed2006

[Arbuscular mycorrhizal fungal growth on citrus roots and its correlations with soil available phosphorus content and phosphatase activity].

In 2004, a field investigation was made on the mycorrhizal infection rate, spore density, soil available phosphorus content, and soil phosphatase activity in the Guoqing No. 1 (Citrus unshiu )/trifoliate orange (Poncirus trifoliata) and Guoqing No. 4 (C. unshiu)/trifoliate orange (P. trifoliata) plantations, aimed to approach the correlations between the arbuscular mycorrhizal fungal growth on citrus roots and the available phosphorus content and phosphatase activity in rhizosphere soil. The results showed that the annual variation of mycorrhizal infection rate and spore density in the test plantations was in "A" shape, while that of soil available phosphorus content and neutral phosphatase activity was in "V" shape. The mycorrhizal infection rate was significantly positively correlated with spore density (P < 0. 01), and negatively correlated with soil available phosphorus content (P < 0.01), indicating that higher spore density and lower soil available ghosphorus content could accelerate the mycorrhizai infection on citrus roots. The pore density was significantly negatively correlated with soil available phosphorus content (P < 0.01) while positively correlated with soil total and neutral phosphatase activity (P < 0.01), suggesting that soil available phosphorus could inhibit the increase of spore density, while soil total and neutral phosphatase activity could stimulate it. The mineralization of soil organic phosphorus in citrus plantations was mainly depended on soil neutral phosphatase activity.

Animals↗
PubMed2006

[Production of polyclonal and monoclonal antibodies against citrus tristeza virus and their efficiency for the detection of the virus].

Citrus tristeza virus (CTV) was purified from a citrus sample by a modified protocol, and the yield was about 1 mg from 100 g citrus tissues. Polyclonal antibody was prepared by immunizing rabbits with the purified CTV preparation with a titer 1:25600 in indirect ELISA test. Eighteen hybridoma-cell lines secreting monoclonal antibodies (MAbs) against CTV were screened after the fusion of mouse myeloma cells (SP2/0) with spleen cells from BALB/c immunized with the virus preparation. Four hybridoma-cell lines were selected randomly for later analysis. The results indicated that the titers of ascetic fluids against these hybridoma cell lines ranged from 1:51200 to 1:204800 in indirect ELISA, and their isotypes and subclasses were IgG2a for 2G and 3H and IgG2b for IE and 4H. These four Mabs were used to detect CTV in citrus samples in different sources. Results showed that TAS-ELISA with polyclonal antibody as trapping antibody and monoclonal antibody as testing antibody had a higher specificity and sensitivity than PAS-ELISA. Four Mabs showed different intensities of serological reaction with different CTV isolates. However, much work remains for realizing the characteristics and the serological relationships among these isolates.

Animals↗
PubMed1980

Determination of Geotrichum mold in citrus juices: collaborative study.

The sieve mesh sizes (Nos. 8, 16, and 230) specified in the official method for the Geotrichum mold count of fruits and vegetables, 44.079, are inadequate for citrus juices. Citrus tissue passes through the larger mesh screens and clogs the fine mesh No. 230 sieve. The fine citrus tissue prevents the separation of the mold from the product and the liquid. The proposed method changes the sieve series to Nos. 40, 140, and 230 mesh. A compromise is reached which permits the concentration of mold along with the citrus tissue and the elimination of the excess liquid. The method has been adopted official first action.

Beverages↗
PubMedDate not supplied

Determination of thiabendazole residues in whole citrus fruits by liquid chromatography with fluorescence detection.

An existing liquid chromatographic (LC) method for determination of thiabendazole (TBZ) residues in or on whole green bananas and potatoes was applied to whole, unwashed citrus fruits. The method is applicable for determining TBZ residues in whole oranges, grapefruits, tangerines, and lemons. TBZ is extracted from citrus homogenate with ethyl acetate, and the extract is cleaned up on a cation-exchange, solid-phase extraction column. The purified extract is analyzed by LC with a cation-exchange column and fluorescence detection. Average recovery of TBZ from whole citrus fruits fortified with TBZ at 0.05-20 ppm was 96%. The assay provides a simple, rapid, and sensitive method for monitoring TBZ residues in whole citrus fruits.

Chromatography, Ion Exchange↗
PubMed1997

Occurrence of citrus viroids in Costa Rica.

A survey for citrus viroids was conducted in the major citrus commercial growing areas in Costa Rica. Screening of 36 sweet orange and 12 lemon trees resulted in the detection of members of four of the five citrus viroid groups as determined by nucleic acid hybridization using specific RNA probes and polymerase chain reaction (PCR) using specific oligonucleotide primers. CEVd, CVd-IIa, CVD-IIb and CVd-III viroids were found to be widespread in the three main regions of commercial citrus production. CVd-Ib was only found in lemon in Nicoya.

Citrus↗
PubMed2005

Leaf volatile compounds of six citrus somatic allotetraploid hybrids originating from various combinations of lime, lemon, citron, sweet orange, and grapefruit.

Volatile compounds were extracted by a pentane/ether (1:1) mixture from the leaves of six citrus somatic allotetraploid hybrids resulting from various combinations of lime, lemon, citron, sweet orange, and grapefruit. Extracts were examined by gas chromatography-mass spectrometry (GC-MS) and compared with those of their respective parents. All hybrids having an acid citrus parent exhibit the same relative contents in hydrocarbons and oxygenated compounds as the acid citrus, while the (grapefruit + orange) hybrid behaves similarly to its two parents. When volatile compound contents (microg g(-1)) are examined in detail, several behaviors are encountered in hybrids and seem to depend on the presence/absence of the considered parental compound and on the corresponding hybrid combination. Meanwhile, the sesquiterpene hydrocarbons are present in all hybrids at concentrations systematically lower than those of the highest parental producers. Statistical analyses show that hybrids exhibit hardly discriminable aromatic profiles, meaning that no strong dominance of one or the other parent was observed in hybrids with regards to the leaf volatile compound production.

Citrus↗
PubMed2005

Pesticide residues survey in citrus fruits.

The use of pesticides is widespread in citrus fruits production for pre- and post-harvest protection and many chemical substances may be applied in order to control undesirable moulds or insects. A survey was carried out to evaluate levels of pesticide residues in citrus fruits. Two multiresidue analytical methods were used to screen samples for more than 200 different fungicides, insecticides and acaricides. A total of 240 samples of citrus fruits including lemon, orange, mandarin, grapefruit, lime, pomelo and kumquat were taken in various markets in the Geneva area during the year 2003. Ninety-five percent of the 164 samples issued from classical agriculture contained pesticides and 38 different compounds have been identified. This high percentage of positive samples was mainly due to the presence of two post-harvest fungicides, imazalil and thiabendazole, detected in 70% and 36% of samples respectively. Only three samples exceeded the Swiss maximum residue limits (MRLs). Fifty-three samples sold with the written indication "without post-harvest treatment" were also controlled. Among theses samples, three exceeded the Swiss MRLs for penconazole or chlorpyrifos and 18 (34%) did not respect the written indication since we found large amounts of post-harvest fungicides. Finally, 23 samples coming from certified organic production were analysed. Among theses samples, three contained small amounts of pesticides and the others were pesticides free.

Agriculture↗
PubMed2003

Expressed sequence enrichment for candidate gene analysis of citrus tristeza virus resistance.

Several studies have reported markers linked to a putative resistance gene from Poncirus trifoliata ( Ctv-R) located at linkage group 4 that confers resistance against one of the most important citrus pathogens, citrus tristeza virus (CTV). To be successful in both marker-assisted selection and transformation experiments, its accurate mapping is needed. Several factors may affect its localization, among them two are considered here: the definition of resistance and the genetic background of progeny. Two progenies derived from P. trifoliata, by self-pollination and by crossing with sour orange ( Citrus aurantium), a citrus rootstock well-adapted to arid and semi-arid areas, were used for linkage group-4 marker enrichment. Two new methodologies were used to enrich this region with expressed sequences. The enrichment of group 4 resulted in the fusion of several C. aurantium linkage groups. The new one A(7+3+4) is now saturated with 48 markers including expressed sequences. Surprisingly, sour orange was as resistant to the CTV isolate tested as was P. trifoliata, and three hybrids that carry Ctv-R, as deduced from its flanking markers, are susceptible to CTV. The new linkage maps were used to map Ctv-R under the hypothesis of monogenic inheritance. Its position on linkage group 4 of P. trifoliata differs from the location previously reported in other progenies. The genetic analysis of virus-plant interaction in the family derived from C. aurantium after a CTV chronic infection showed the segregation of five types of interaction, which is not compatible with the hypothesis of a single gene controlling resistance. Two major issues are discussed: another type of genetic analysis of CTV resistance is needed to avoid the assumption of monogenic inheritance, and transferring Ctv-R from P. trifoliata to sour orange might not avoid the CTV decline of sweet orange trees.

Chromosome Mapping↗
PubMed1982

Mutagenicity of hydrolysates of citrus fruit juices.

Hydrolysates of citrus fruit juice were mutagenic according to the Ames test. The citrus fruit juices were hydrolysed with 1 M HCl, hesperidinase, naringinase and human intestinal bacteria. The hydrolysates were successively extracted with n-hexane, chloroform, diethyl ether and ethyl acetate. The mutagenicities of extracts were assayed by the Ames test, and the mutagens were analysed by gas chromatography and mass spectrometry (GC-MS). Mutagenicities of hydrolysates of citrus fruit juice were found in both the chloroform extracts and the ether extracts. The chloroform extracts were mutagenic to TA98 and TA100 with S9 mix, and the ether extracts were mutagenic to TA98 and TA100 with or without S9 mix. Some known flavonols such as kaempferol and quercetin were detected in the extracts of the hydrolysates by GC-MS. It is suggested that the mutagenicity of the extracts originated from those flavonols in the citrus fruit juice.

Flavonoids↗
PubMed2001

Differences in sensitization rates to outdoor aeroallergens, especially citrus red mite (Panonychus citri), between urban and rural children.

BACKGROUND: A recent investigation has suggested that citrus red mite (Panonychus citri, CRM) is the most important allergen in citrus-cultivating farmers with asthma and allergic rhinitis. OBJECTIVE: A cross-sectional survey was performed to evaluate the prevalence of asthma and chronic rhinitis symptoms and sensitization to common indoor and outdoor aeroallergens, including CRM and Japanese cedar pollen, in rural and urban Korean children. METHODS: A total of 2,055 children (1,055 subjects living in rural areas with citrus farms and 1,000 controls in urban areas without citrus farms) were enrolled. They were evaluated by a questionnaire, and by skin prick tests with 13 common indoor and outdoor aeroallergens, including CRM and Japanese cedar pollen. RESULTS: The prevalence of wheezing and chronic rhinitis symptoms during the last 12 months was 8.3% and 35.7% in the rural children and 10.5% and 22.4% in the control group. The most common sensitizing allergens in order of decreasing frequency were Dermatophagoides pteronyssinus (26.6%), Dermatoplagoides farinae (22.7%), CRM (14.2%), cockroach (11.3%), and Japanese cedar pollen (9.7%) among the rural children, but the sensitization rates to CRM and Japanese cedar pollen were 1.3% and 0.2% among the control children, respectively. The prevalence of wheeze during the last 12 months was not different between rural children with sensitization to CRM or Japanese cedar pollen and those without sensitization (5.4% vs 6.1%; 6.9% vs 5.9%). However, the prevalence of chronic rhinitis during the last 12 months was higher among those with sensitization to CRM or to Japanese cedar pollen than among those without sensitization (40.8% vs 34.4%; 51.5% vs 33.5%). CONCLUSIONS: CRM is a common sensitizing allergen in rural children, and the sensitization rates to outdoor aeroallergens, especially CRM and Japanese cedar pollen, are very different between children from rural and urban areas in Korea.

Adolescent↗
PubMed2002

Identification of a grapefruit cDNA belonging to a unique class of citrus dehydrins and characterization of its expression patterns under temperature stress conditions.

Citrus fruits are sensitive to low temperatures and this often results in the development of chilling injuries during postharvest storage. In order to gain more insight into the molecular mechanisms involved in the acquisition of fruit chilling tolerance, we initiated a grapefruit (Citrus paradisi, cv. Marsh Seedless) flavedo cDNA sequencing project and used it to identify a cDNA similar to other Poncirus trifoliata and Citrus unshiu dehydrin genes reported to be responsive to low temperatures. The grapefruit dehydrin cDNA, designated cor15, encodes a predicted polypeptide of 15.1 kDa, that is almost completely identical with other reported citrus dehydrin proteins, except that it contains two large amino acid repeats, whereas P. trifoliata COR11 has only one such repeat and P. trifoliata COR19 and C. unshiu COR19 have three repeats. Together, the various grapefruit, P. trifoliata and C. unshiu dehydrins form a closely related and unique dehydrin gene family that differs from most other plant dehydrins in having an unusual K-segment similar to that of gymnosperms and in having a serine cluster (S-segment) at an unusual position at the carboxy-terminus. The grapefruit cor15 gene is consistently expressed in the fruit peel tissue at harvest, but its message levels dramatically decrease during storage at 2 degrees C. However, a pre-storage hot water treatment, which enhances fruit chilling tolerance, elicited retention of the constant level of cor15 gene expression during cold storage and eliminated its decline. The hot water treatment had no inductive effect on cor15 gene expression when the fruit were held at non-chilling temperatures. The effects of other stresses, such as exposure to ethylene, UV irradiation and wounding, on cor15 gene expression, were temporary and persisted for 1-2 days after the treatments.

Journal Article↗
PubMed1987

Chlorophyll catabolism in senescing plant tissues: In vivo breakdown intermediates suggest different degradative pathways for Citrus fruit and parsley leaves.

High-pressure liquid chromatography was used to separate chlorophyll derivatives in acetone extracts from senescing Citrus fruit peel, autumnal Melia azedarach L. leaves, and dark-held detached parsley (Petroselinum sativum L.) leaves. Chlorophyllide a and another polar, dephytylated derivative accumulated in large amounts in senescing Citrus peel, particularly in fruit treated with ethylene. Ethylene also induced a 4-fold increase in the specific activity of Citrus chlorophyllase (chlorophyll chlorophyllidohydrolase, EC 3.1.1.14). Detailed kinetics based on a hexane/acetone solvent partition system showed that the in vivo increase in dephytylated derivatives coincided with the decrease in total chlorophyll. Polar, dephytylated derivatives accumulated also in senescing Melia leaves. Senescing parsley leaves revealed a very different picture. The gradual disappearance of chlorophyll a was accompanied by an increase in pheophytin a and by the transient appearance of several phytylated derivatives. Only pheophytin a and an adjacent peak were left when all the chlorophyll a had disappeared. The pathways for breakdown of chlorophyll in the Citrus and parsley senescence systems are discussed.

Journal Article↗
PubMed2001

In Vitro and In Vivo Lipoprotein Antioxidant Effect of a Citrus Extract and Ascorbic Acid on Normal and Hypercholesterolemic Human Subjects.

Polyphenols and particularly flavonoids are well known in vitro antioxidants. Their consumption in foods has been shown to decrease the risk of heart disease in epidemiological studies. Because flavonoids are consumed with vitamin C in the diet, the combination may prove to be more beneficial than either alone. The combination of citrus extract and vitamin C was found to produce a synergistic antioxidant effect in an in vitro lipoprotein oxidation model. In a double-blind, placebo-controlled study with 26 normal and hypercholesterolemic subjects, the citrus extract and vitamin C, but not vitamin C or vitamin E alone, significantly lowered triglycerides. The combination of citrus extract and vitamin C increased the lag time of lipoprotein oxidation, compared with vitamin C alone or a placebo, and was a significantly better antioxidant than vitamin E. These results and other published studies are highly suggestive of in vitro and in vivo antioxidant synergism between citrus extract and vitamin C.

Journal Article↗
PubMed1997

Citrus response to salinity: growth and nutrient uptake.

To determine the effects of salinity on relative growth rate (RGR), net assimilation rate on a leaf weight basis (NAR(w)), leaf weight ratio (LWR), and nutrient uptake and utilization of citrus, we grew four citrus rootstocks (sour orange, Cleopatra mandarin, Carrizo citrange and Citrus macrophylla) in nutrient solutions containing 0, 10, 20, 40 or 80 mM NaCl for 20, 40 or 60 days. For each element analyzed, specific absorption rate (SAR) and specific utilization rate on a leaf basis (SUR(L)) were calculated for the period between Days 40 and 60. Relative growth rate decreased with time for all treatments and rootstocks. Salt treatment significantly reduced both RGR and NAR(w), whereas LWR showed no definite trend. In all rootstocks, NAR(w), but not LWR, was significantly correlated with RGR, indicating that NAR(w) was an important factor underlying the salinity-induced differences in RGR among the citrus rootstocks. At Day 60, salinity had a significant effect on leaf concentrations of Cl, Na, K, Ca, Mg, P, Fe, Mn and Zn and on the SAR and SUR(L) of most elements. In general, RGR was correlated with SAR and SUR(L). Therefore, in addition to osmotic effects and the inhibitory effects of high concentrations of Cl(-) and Na(+), an imbalance of essential nutrients may also contribute to the reduction in plant growth under saline conditions.

Journal Article↗
PubMed1966

Differentiation between indoleacetic Acid and the citrus auxin by column chromatography.

A gradient elution column chromatography technique and a step-wise technique succeeded in differentiating between IAA and the citrus auxin. IAA was eluted ahead of the citrus auxin in both systems. The highest Avena curvature ever obtained from the citrus auxin occurred after the auxin had passed through the 2 purification techniques and a paper chromatography step. This is probably due to the elimination of inhibitors. Fluorometric assay, Ehrlich's reaction, thin-layer chromatography, and biological assay were used for the detection of IAA or citrus auxin in the column eluates.

Journal Article↗