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1.
Luqman Qurata Aini Hisae Hirata Shinji Tsuyumu 《Journal of General Plant Pathology》2010,76(2):132-142
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Hsin-Cheng Lin Mu-Kuei Chu Yuang-Chuen Lin Wen-Ling Deng Hsiang Chang Shih-Tien Hsu Kuo-Ching Tzeng 《European journal of plant pathology / European Foundation for Plant Pathology》2011,130(2):143-154
The typical citrus canker lesions produced by Xanthomonas axonopodis pv. citri are erumpent, callus-like, with water-soaked margins. Three novel atypical symptom-producing variants of X. axonopodis pv. citri were described recently in Taiwan. Only the variant designated as Af type produces typical erumpent canker lesions on Mexican lime (Citrus aurantifolia) but induces flat necrotic with water-soaked margin lesions on grapefruit leaves (C. paradisi). Two homologous pthA were cloned and characterized from strains XW19 (a typical canker lesion producing strain) and XW47 (a strain of Af type). The pthA homolog from XW19 was transformed into XW47. The transformant of XW47 induced typical erumpent canker lesions on grapefruit
leaves. Sequence analyses of transformants XW19 and XW47 revealed over 99% homology in nucleotide and deduced amino acid sequences
compared with pthA homologs deposited in GenBank. The amino acid residues located at positions 49, 286, 742 and 767 of PthA were different between
XW47 and XW19. The PthA mutants with a single amino acid substitution at each of these four positions were constructed by
site-directed mutagenesis. Modified PthA (S286P) from XW47 in transformant 47SP induced erumpent canker lesions on grapefruit
leaves, whereas another modified PthA (P286S) from XW19 in transformant 47PS only induced flat necrotic lesions. These results
suggested that a single amino acid substitution from either serine to proline or proline to serine at position 286 of PthA
can alter canker formation by X. axonopodis pv. citri on grapefruit leaves. 相似文献
3.
Yongxiang Zhang Ewen M. Callaway Jeffrey B. Jones Mark Wilson 《European journal of plant pathology / European Foundation for Plant Pathology》2009,124(3):379-390
The plasmid pUFZ75 conferred constitutive GFP expression on the bacterial pathogen Xanthomonas euvesicatoria (syn. X. campestris pv. vesicatoria). Colonisation of the tomato phyllosphere and invasion of tomato leaves by X. euvesicatoria was examined using both fluorescence and confocal laser scanning microscopy. Xanthomonas euvesicatoria established a limited population on the tomato leaf surface, primarily occupying the depressions between epidermal cells
and around the stomata, prior to invasion of the leaf via the stomata and subsequent growth within the substomatal chamber
and the leaf apoplast. Additionally, hrp-gfp fusions were used to report on the temporal and spatial expression of hrp genes during epiphytic colonisation and invasion. Xanthomonas euvesicatoria cells carrying hrpG- and hrpX-gfp reporter constructs were not fluorescent in vitro on non-hrp-inducing LB agar but did exhibit a low level of fluorescence on the leaf surface within 24 h of inoculation, particularly
in the vicinity of stomata. Cells carrying hrpG- and hrpX-gfp fusions exhibited high levels of fluorescence 72 h after inoculation in the substomatal chamber and the leaf apoplast. Cells
carrying the hrpF-gfp fusion were slightly fluorescent on LB agar and showed no further increase in fluorescence on the leaf surface by 24 h after
inoculation, but did show a significant increase in fluorescence 72 h after inoculation in the substomatal chamber and apoplast.
The apparent low-level induction of the regulators hrpG and hrpX on the tomato leaf surface may suggest that some of the genes of the X. euvesicatoria HrpG/HrpX regulon are up- or down-regulated prior to invasion of the stomata while still on the leaf surface. 相似文献
4.
The clustered hrp genes encoding the type III secretion system in the Japanese strains MAFF301237 and MAFF311018 of Xanthomonas oryzae pv. oryzae were sequenced and compared. The strains differ in their pathogenicity, location, and year of isolation. A 30-kbp sequence comprising 29 open reading frames (ORFs) was identical in its structural arrangement in both strains but differed from X. campestris pv. campestris, X. axonopodis pv. citri, and X. axonopodis pv. glycines in certain genes located between the hpaB-hrpF interspace region. The DNA sequence and the putative amino acid sequence in each ORF was also identical in both X. oryzae pv. oryzae strains as were the PIP boxes and the relative sequences. These facts clearly showed that the structure of the hrp gene cluster in X. oryzae pv. oryzae is unique. 相似文献
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The effects of some fungicides used against citrus diseases, on mycelial growth and conidial germination of Isaria farinosa (Holmsk.) Fries [Sordariomycetes: Hypocreales] and also on the pathogenicity of the fungus on citrus mealybug, Planococcus citri (Risso), were determined. Systemic fungicides such as tebuconazole, penconazole and nuarimol were the most effective as regards
both conidial germination and mycelial growth. Protective fungicides such as captan, chlorothalonil, mancozeb and propineb
inhibited conidial germination at between 1 and 5 μg ml−1 concentration, but captan, chlorothalonil and propineb did not inhibit the mycelial growth at 5,000 μg ml−1. Mancozeb inhibited mycelial growth between 2,500 and 5,000 μg ml−1. Sulphur and copper oxychloride did not inhibit the fungus even at very high concentrations. Sulphur, copper oxychloride,
fosetyl-al, chlorothalonil and carbendazim did not decrease the mortality percentage caused by I. farinosa. Tebuconazole, penconazole and mancozeb were the most effective and respectively reduced the mortality from 83% to 33%, 28%
and 30% in the ovisacs, from 81% to 29%, 27% and 29% in the 1st instar larvae, and from 84% to 34% in the adult females. 相似文献
9.
Masato?Kawabe Kohei?Mizutani Takanobu?Yoshida Tohru?Teraoka Katsuyoshi?Yoneyama Isamu?Yamaguchi Tsutomu?Arie
We selected a reduced-pathogenicity mutant of Fusarium oxysporum f. sp. lycopersici, a tomato wilt pathogen, from the transformants generated by restriction enzyme-mediated integration (REMI) transformation. The gene tagged with the plasmid in the mutant was predicted to encode a protein of 321 amino acids and was designated FPD1. Homology search showed its partial similarity to a chloride conductance regulatory protein of Xenopus, suggesting that FPD1 is a transmembrane protein. Although the function of FPD1 has not been identified, it does participate in the pathogenicity of F. oxysporum f. sp. lycopersici because FPD1-deficient mutants reproduced the reduced pathogenicity on tomato.The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession number AB110097 相似文献
10.
Ahmed A. Kheder Yasunori Akagi Hajime Akamatsu Konomi Yanaga Nitaro Maekawa Hiroshi Otani Takashi Tsuge Motoichiro Kodama 《Journal of General Plant Pathology》2012,78(1):30-38
The tomato pathotype of Alternaria alternata (A. arborescens) produces the dark brown to black pigment melanin, which accumulates in the cell walls of hyphae and conidia. Melanin has
been implicated as a pathogenicity factor in some phytopathogenic fungi. Here, two genes of the tomato pathotype for melanin
biosynthesis, ALM1 and BRM2-1, which encode a polyketide synthetase and a 1,3,8-trihydroxynaphthalene (THN) reductase, respectively, have been cloned and
disrupted in the pathogen. The gene-disrupted mutants, alm1 and brm2-1, had albino and brown phenotypes, respectively. The wild-type and the mutants caused the same necrotic lesions on the leaves
after inoculation with spores. These results suggest that melanin is unlikely to play a direct role in pathogenicity in the
tomato pathotype A. alternata. Scanning electron microscopy revealed that the conidia of both mutants have much smoother surfaces in comparison to the
wild-type. The conidia of those mutants were more sensitive to UV light than those of the wild-type, demonstrating that melanin
confers UV tolerance. 相似文献
11.
Hiroshi Shiotani Terutaka Yoshioka Masashi Yamamoto Ryoji Matsumoto 《Journal of General Plant Pathology》2008,74(2):133-137
Susceptibility to Xanthomonas
axonopodis pv. citri of a citrus cybrid, in which the nuclear and cytoplasmic genomes were derived from Citrus
sinensis and C. unshiu, respectively, was evaluated. Bacterial growth in the leaves of the cybrid was similar to that in C. sinensis after pin-prick inoculation throughout the experiment, whereas growth was greater than that in C. unshiu from 8 days after inoculation. Lesion expansion and pustules that later developed from the lesions on the cybrid and on C. sinensis also appeared to be greater than those on C. unshiu. The incidence of citrus canker disease caused by the bacteria on the cybrid trees was in the field was equivalent to that
on C. sinensis but was severer than on C. unshiu. These results indicate that the nuclear genome of the cybrid plays a critical role in susceptibility to citrus canker disease.
However, the pathogenicity gene pthA of the bacteria is not likely to be involved in the difference in susceptibility to the bacteria between C. unshiu and C. sinensis because their susceptibility to a pthA-deficient mutant of the bacteria also differs. 相似文献
12.
Daniela Portz Eckhard Koch Alan J. Slusarenko 《European journal of plant pathology / European Foundation for Plant Pathology》2008,122(1):197-206
The volatile antimicrobial substance allicin (diallylthiosulphinate) is produced in garlic when the tissues are damaged and
the substrate allicin (S-allyl-l-cysteine sulphoxide) mixes with the enzyme alliin-lyase (E.C.4.4.1.4). Allicin undergoes thiol-disulphide exchange reactions
with free thiol groups in proteins and it is thought that this is the basis of its antimicrobial action. At 50 μg ml-1, allicin in garlic juice inhibited the germination of sporangia and cysts and subsequent germ tube growth by Phytophthora infestans both in vitro and in vivo on the leaf surface. Disease severity in P. infestans-infected tomato seedlings was also reduced by spraying leaves with garlic juice containing allicin over the range tested
(55–110 μg ml−1) with an effectiveness ranging from approximately 45–100%. Similarly, in growth room experiments at concentrations from 50–1,000 μg
ml−1, allicin in garlic juice reduced the severity of cucumber downy mildew caused by Pseudoperonospora cubensis by approximately 50–100%. These results suggest a potential for developing preparations from garlic for use in specialised
aspects of organic farming, e.g. for reducing pathogen inoculum potential and perhaps for use under glass in horticulture. 相似文献
13.
Betiana S. Garavaglia Cecilia G. Garofalo Elena G. Orellano Jorgelina Ottado 《European journal of plant pathology / European Foundation for Plant Pathology》2009,123(1):91-97
Hsp70 and Hsp90 expression in response to high and low temperatures was studied in orange, the host plant of Xanthomonas axonopodis pv. citri and in a non-host resistant plant, pepper. As expected in both plants, the expression of these chaperones was induced at
high temperatures while at cold temperatures the response was chaperone and plant-dependent. Expression of Hsp70 and Hsp90
was analysed during citrus canker and no changes in their levels could be observed whereas pepper plants infiltrated with
the phytopathogen showed an increase in the levels of both chaperones. These results suggest that no changes in Hsp70 and
Hsp90 expression are necessary during the disease while they are increased in non-host resistance. 相似文献
14.
Alessandro Vitale Gabriella Cirvilleri Anna Panebianco Filomena Epifani Giancarlo Perrone Giancarlo Polizzi 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(4):483-487
Thirty-two isolates belonging to black aspergilli (Aspergillus section Nigri) associated to vine canker disease of grapevine were collected in seven vineyards located in southeastern Sicily (Italy).
Molecular analysis was performed to identify the isolates by multilocus sequence analysis. Amplification of part of the β-tubulin
gene (benA) and partial calmodulin (CaM) gene were performed using the Bt2a, Bt2b and CL1, CL2A primers, respectively. Molecular characterisation showed a high distribution
of Aspergillus niger “aggregate” species on grapes in Sicily and in particular of A. niger (21 isolates), A. tubingensis (9 isolates), and A. carbonarius (2 isolates). The 21 isolates of A. niger found to belong within the newly described cryptic species A. awamori. Six isolates (3 of A. tubingensis, 2 of A. carbonarius, and 1 of A. niger) were used in pathogenicity studies on mature canes of cv. Italia grape. All species caused Aspergillus vine canker equally
well, with no differences in virulence. 相似文献
15.
Rita M. De Miccolis Angelini Wassim Habib Caterina Rotolo Stefania Pollastro Francesco Faretra 《European journal of plant pathology / European Foundation for Plant Pathology》2010,128(2):185-199
Resistance to the fungicide boscalid in laboratory mutants of Botryotinia fuckeliana (Botrytis cinerea) was investigated. The baseline sensitivity to boscalid was evaluated in terms of colony growth (EC50 = 0.3–3 μg ml−1; MIC = 10–30 μg ml−1) and conidial germination (EC50 = 0.03–0.1 μg ml−1; MIC = 1–3 μg ml−1) tests. Mutants were selected in vitro from wild-type strains of the fungus on a fungicide-amended medium containing acetate as a carbon source. Mutants showed
two different levels of resistance to boscalid, distinguishable through the conidial germination tests: low (EC50 ∼ 0.3 μg ml−1, ranging from 0.03 to 1 μg ml−1; MIC > 100 μg ml−1) and high (EC50 > 100 μg ml−1) resistance. Analysis of meiotic progeny from crosses between resistant mutants and sensitive reference strains showed that
resistant phenotypes were due to mutations in single major gene(s) inherited in a Mendelian fashion, and linked with both
the Daf1 and Mbc1 genes, responsible for resistance to dicarboximide and benzimidazole fungicides, respectively. Gene sequence analysis of
the four sub-units of the boscalid-target protein, the succinate dehydrogenase enzyme, revealed that single or double point
mutations in the highly conserved regions of the iron-sulphur protein (Ip) gene were associated with resistance. Mutations
resulted in proline to leucine or phenylalanine replacements at position 225 (P225L or P225F) in high resistant mutants, and
in a histidine to tyrosine replacement at position 272 (H272Y) in low resistant mutants. Sequences of the flavoprotein and
the two transmembrane sub-units of succinate dehydrogenase were never affected. 相似文献
16.
Mikiko Harada Satoshi Ishikawa Tadaaki Hibi Kyoko Watanabe 《Journal of General Plant Pathology》2008,74(4):341-343
In 2003–2004, anthracnoses of Enkianthus campanulatus and Rhynchosia acuminatifolia were found for the first time in Kanagawa Prefecture and Tokyo in Japan. These pathogens were identified as Colletotrichum gloeosporioides based on their pathogenicity, morphology and ribosomal DNA spacer sequences.
Results were presented at the annual meeting of The Phytopathological Society of Japan in 2004. 相似文献
17.
Khalid A. Hussein Mohamed A. A. Abdel-Rahman Ahmed Y. Abdel-Mallek Saad S. El-Maraghy Jin Ho Joo 《Phytoparasitica》2012,40(2):117-126
The greater wax moth Galleria mellonella L. (Lepidoptera: Pyralidae) is occasionally found in beehives and is a major pest of stored wax. Entomopathogenic fungi have
recently received attention as possible biocontrol elements for certain insect pests. In this study, 90 isolates of Beauveria bassiana and 15 isolates of Metarhizium anisopliae were screened for proteases and lipases production. The results showed significant variations in the enzymatic action between
the isolates. In the bioassay, the selected isolates evinced high virulence against the 4th instar of the G. mellonella larvae. The isolates BbaAUMC3076, BbaAUMC3263 and ManAUMC3085 realized 100% mortality at concentrations of 5.5 × 106 conidia ml−1, 5.86 × 105 conidia ml−1, and 4.8 × 106 conidia ml−1, respectively. Strong enzymatic activities in vitro did not necessarily indicate high virulence against the tested insect pest. The cuticle of the infected larvae became dark
and black-spotted, indicating direct attack of fungus on the defense system of the insects. The LC50 values were 1.43 × 103, 1.04 × 105 and 5.06 × 104 for Bba3263AUMC, Bba3076AUMC and Man3085AUMC, respectively, and their slopes were determined by computerized probit analysis
program as 0.738 ± 0.008, 0.635 ± 0.007 and 1.120 ± 0.024, respectively. 相似文献
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Yoshiaki Harimoto Takayoshi Tanaka Motoichiro Kodama Mikihiro Yamamoto Hiroshi Otani Takashi Tsuge 《Journal of General Plant Pathology》2008,74(3):222-229
The apple pathotype of Alternaria alternata produces the cyclic depsipeptide AM-toxin and causes Alternaria blotch of apple. Previously, we cloned AMT2 from the apple pathotype as an orthologue of AFTS1, which is required for biosynthesis of the decatrienoic acid ester AF-toxin I of the strawberry pathotype. These genes were
predicted to encode aldo-keto reductases involved in biosynthesis of a common precursor, 2-hydroxy-isovaleric acid, of AF-toxin
I and AM-toxin. In this study, we analyzed the function of AMT2 in AM-toxin biosynthesis in the apple pathotype. DNA gel blot analysis of the apple pathotype strain IFO8984 with five restriction
enzymes suggested that this strain has a single copy of AMT2 in the genome. However, gene disruption experiments showed that IFO8984 probably has three copies of AMT2. We made mutants having one or two copies of AMT2 disrupted. The single-copy mutants produced less AM-toxin than did the wild type and were still as pathogenic as the wild
type. The two-copy mutants produced trace or undetectable amounts of AM-toxin and were markedly reduced in pathogenicity.
Thus, AMT2 was verified to be required for AM-toxin biosynthesis and hence pathogenicity. The fact that the two-copy mutants have a
remaining copy of AMT2 suggests that multiple copies of AMT2 are prerequisite for the pathogen to produce enough AM-toxin for full pathogenicity. 相似文献
20.
Franklin Behlau Jeffrey B. Jones Monty E. Myers James H. Graham 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(2):259-270
Streptomycin has been tested as an alternative to copper bactericides, which are routinely used for the control of citrus
canker (Xanthomonas citri subsp. citri, Xcc) in citrus producing areas where the disease is endemic. A major concern is that excessive use of copper as a bactericide
may lead to development of copper-resistant strains of Xcc. In this study, we developed a semi-selective medium to recover
copper or streptomycin-resistant strains of Xcc from citrus leaves. The newly developed semi-selective medium was used to
monitor the effect of a 21-day-interval copper or streptomycin spray program on Xcc for three consecutive seasons and on citrus
epiphytic bacterial populations for two seasons in a commercial grapefruit grove. Although, no copper- or streptomycin-resistant
strains of Xcc were isolated after three seasons, we observed a significant increase over time in the frequency of citrus
epiphytic bacteria resistant to these chemicals. Overall, the proportion of epiphytic bacteria resistant to streptomycin on
treated and untreated leaves was proportionally lower than the copper-resistant bacterial population. When application of
each bactericide was suspended for the season, the proportion of bactericide-resistant bacteria in the epiphytic population
decreased to that of the non-treated bacterial population. Availability of an alternative bactericide, such as streptomycin,
to integrate into a copper-based program would reduce the amount of each bactericide sprayed in citrus orchards and possibly
lower the selection pressure for bacterial resistance to these chemicals. 相似文献