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1.
Phosphate was shown to reverse the in vitro activity of phosphonate ions against P. capsici (strain 375) more efficiently in liquid than in solid media. Phosphonate transport by mycelia incubated in aqueous solutions was enhanced by a previous phosphate starvation and the presence of K+ cations. The intracellular phosphonate concentration reached a constant level and this concentration, which is a function of the external concentration, fits a hyperbolic relationship. Phosphonate transport was greatly stimulated when mycelia were incubated in modified Ribeiro's medium. In the absence of any phosphorus source in the growth medium, the phosphate content of mycelia at stationary phase of growth decreased. This sign of phosphate deficiency was intensified in the presence of phosphonate. 相似文献
2.
Pre- and post-infection activities of phosphonate and fungicides (azoxystrobin, chlorothalonil, cyazofamid, copper hydroxide, and copper sulfate) against white powdery rot on fig leaves caused by Phytophthora palmivora were determined. Phosphonate and fungicides were applied at 3, 7, or 14 days before inoculation and 16, 24, or 40 h after inoculation. Phosphonate and four fungicides (except for chlorothalonil) had protectant activity for up to 14 days before inoculation. Protectant activity between phosphonate and the four fungicides did not differ significantly. These fungicides did not have a curative activity, whereas only phosphonate had a curative activity when applied 16 h after inoculation. The pre-infection activity of phosphonate was determined in fig fields. Phosphonate provided excellent protectant activity, and its activity did not differ significantly from that of the copper fungicides. The activity of phosphonate in the life cycle of P. palmivora was compared with that of the five fungicides. Half-maximal effective concentration of the inhibition of mycelial growth was low for phosphonate, chlorothalonil, and the two copper fungicides. Mycelial growth was least affected by azoxystrobin and cyazofamid, but n-propyl gallate, an alternative oxidase inhibitor, in combination with these fungicides, significantly inhibited mycelial growth. Sporangium formation was sensitive to all compounds. Germination of encysted zoospores was sensitive to azoxystrobin, cyazofamid, and chlorothalonil and least sensitive to phosphonate and the two copper fungicides. The activity of phosphonate on mycelial growth and sporulation of P. palmivora suggests it has potential for controlling the disease. 相似文献
3.
Phosphonate (0.1 mM) significantly reduced growth of Fusarium oxysporum f. sp. cubense (Foc) race 4 grown at an optimal phosphate concentration of 0.3 mM in vitro. At higher phosphate concentrations, closer to physiological conditions within the plant, the sensitivity of Foc race 4 to phosphonate was greatly reduced, with 25 mM phosphonate required to reduce growth by 50% at 1 mM phosphate. Two isolates of Fusarium oxysporum f. sp. dianthi and another race of Foc, race 1, were shown to be similar to Foc race 4 in their sensitivity to phosphonate, while another species of Fusarium, F. avenaceum , was more sensitive to phosphonate in vitro. 相似文献
4.
Phosphonate uptake and distribution were evaluated in tomato plantlets by direct determination and by autoradiography. The rate of root uptake was linear during the 2 h of assay, suggesting active transport of the molecule. Phosphonate was readily taken up through the roots and translocated to the leaves, which contained the molecule within 2 min of root application. Autoradiography showed that phosphonate was transferred apoplastically by veins and progressively entered the lamina by symplastic transport. After a root loading of 2 h, plants were transferred to water and phosphonate levels were evaluated over the following 3 days: the concentrations in roots increased with a corresponding decrease in phosphonate levels in the leaves. These experiments demonstrated the ambimobility of phosphonate. 相似文献
5.
6.
Footrot disease due to Nectria haematococca (anamorph Fusarium solani f.sp. pisi) is an economically important disease of peas globally. However, our ability to predict accurately the likelihood of footrot
infections is limited because there is no method to determine inoculum density prior to planting. In this research, a PCR-based
assay was developed to quantify the pea pathogenicity gene (PEP3), exclusive to highly pathogenic forms of N. haematococca, from DNA extracted from agricultural field soils. The applicability of using quantitative PCR (qPCR) to measure this gene
in soil was validated, and the relationship between PEP3 gene numbers and footrot disease was also studied. Results showed that the quantitative assay is both efficient and specific;
amplification efficiency of the Q-PCR assay for the PEP3 gene was 92%. Gene copy numbers were shown to vary significantly (P = 0.01) between fields, and were positively correlated to the number of spores of pathogenic N. haematococca, and to footrot disease. PEP3 numbers of up to 100 g−1 soil constituted a threshold number for infection—potentially capable of causing economically significant pea footrot disease.
The density of virulent N. haematococca in soil fields capable of causing footrot disease could be determined with a high degree of accuracy, with this assay. It
offers the opportunity for prediction of pea footrot infections in agricultural soils prior to cultivation. 相似文献
7.
L. A. Alvarez D. Gramaje P. Abad-Campos J. García-Jiménez 《European journal of plant pathology / European Foundation for Plant Pathology》2009,124(4):621-635
Three citrus scions were evaluated to determine seasonal changes in susceptibility to infections by Phytophthora citrophthora and Phytophthora nicotianae. In a period of 24 months, the Clementine mandarin cv. Hernandina, the hybrid Fortune mandarin and the sweet orange cv. Lane-Late
were branch-inoculated under field and laboratory conditions. Field studies showed that the cultivars inoculated with P. citrophthora developed the highest lesion areas during March–June (spring) and September–October (autumn) and with P. nicotianae from June to August (summer). However, lesion areas on detached citrus branches did not show a definite pattern of infection
because lesion sizes fluctuated irregularly during the study. The lesion area caused by P. nicotianae in different citrus scions correlated significantly with the monthly mean maximum values of temperature, relative humidity,
and the percentage of the relative water content in the 24-month period of inoculations. In contrast, there was no correlation
between these variables and the extent of colonisation by P. citrophthora. Nevertheless, a significant relationship was observed between lesion areas caused by P. citrophthora from October to May of each year and the same variables that were significant in inoculations with P. nicotianae. Seasonal changes in the susceptibility of citrus cultivars to P. citrophthora and P. nicotianae may facilitate timing of disease control measures to coincide with periods when disease development is greatest. 相似文献
8.
According to the results of bioassay studies, 50 p.p.m. and higher dosages of fentin acetate inhibited the growth of Phytophthora citrophthora in situ. Zoospore movement of P. citrophthora varied between 3 and 15 min at 0.5, 1, 10, 100 and 500 p.p.m. fentin acetate. The fungicide also inhibited fruit infections caused by P. citrophthora zoospores at 5 p.p.m. concentration, and protected citrus seedling roots against infection by the fungus at 20–50 p.p.m. concentrations in water culture. Fruit infection was significantly lower in fentin acetate plots than in those without fungicide applications. Stem infection was 15.5 and 8.3% when fentin acetate was applied one or three times respectively as a soil drench in a lemon orchard, but reached 74.9%) in control plots. Fentin acetate treatment decreased inoculum potential to 1/2 and 1/128 in the root zone from the first to the third application. 相似文献
9.
A severe crown rot of pear trees of cultivar ‘Kondoula’ grafted on quince rootstock was observed in Greece. Isolations from
the affected tissues repeatadly yielded aPhytophthora sp. that was determined by morphological and physiological characteristics to beP. citrophthora. The pathogenicity of two of theP. citrophthora isolates was tested by inoculating trunks of 2-year-old pear trees by mycelial agar disks. Thirty-two days after inoculation
all inoculated trees were infected. Although the pear isolates could not be differentiated from isolates ofP. palmivora orP. nicotianae based on isozyme profiles of α-esterase or lactate dehydrogenase, RAPD profiles with one selected primer differentiated the
pear isolates from the other species and revealed an electrophoretic banding pattern similar to that of aP. citrophthora standard. This is the first report ofP. citrophthora on pear trees in Greece. 相似文献
10.
Hebe Kouyeas 《EPPO Bulletin》1977,7(1):117-124
Stone fruit tree apoplexy in Greece is often caused by Phytophthora spp. Two types of Phytophthora apoplexy of stone fruit tree can be distinguished, one occurring during the hot summer period and usually caused by P. cactorum (Leb. et Cohn) Schröt. or P. citrophthora (R. et E. Smith) Leonian, and a second occurring in winter or early spring, and caused by P. syringae (Kleb.) Kleb. or sometimes P. megasperma Drechsler. Inoculation tests showed P. syringae to be highly pathogenic to apricot and almond, whereas certain clonal rootstock material showed resistance. Measures of control against Phytophthora attacks are given. 相似文献
11.
Francesco Faretra Stefania Pollastro Francisco Sansiviero 《Pest management science》1992,35(2):171-174
‘Aliette’, a formulation of the fungicide fosetyl-aluminium, is moderately active in vitro against the ascomycete Botryotinia fuckeliana (Botrytis cinerea). In contrast, fosetyl-aluminium and related chemicals, such as phosphonic acid and sodium phosphonate, have low efficacy, although it is enhanced by media with low phosphate content. This indicates that the effectiveness of ‘Aliette’ against B. fuckeliana is not due to fosetyl-aluminium but to adjuvants included in the formulation. The genetic basis of differences in sensitivity to ‘Aliette’ was investigated in field and laboratory isolates of B. fuckeliana. Genetic analysis showed that reduced sensitivity to ‘Aliette’ always co-segregated with resistance to benzimidazole fungicides in meiotic progeny of sexual crosses. This indicates that differences in sensitivity to ‘Aliette’ in B. fuckeliana are due to the major gene Mbcl of resistance to benzimidazole fungicides and active adjuvant(s) present in ‘Aliette’ are linked to benzimidazoles by cross-resistance. 相似文献
12.
E. Ilieva F. X. Arulappan R. Pieters 《European journal of plant pathology / European Foundation for Plant Pathology》1995,101(6):623-626
Root and crown rot of raspberry (Rubus idaeus L.) was observed in a plantation at the experimental station of small fruits in Kostinbrod, Bulgaria. Isolates ofPhytophthora spp. were obtained from diseased plants. Colony morphology, growth rates, features of asexual and sexual structures were studied and as a result twoPhytophthora species were identified:Phytophthora citricola Saw. andPhytophora citrophthora (R.E. Sm. & E.H. Sm.) Leonian. Their pathogenicity was confirmed in artificial inoculation experiments. The isozyme (-esterase) patterns ofP. citrophthora andP. citricola isolates from raspberry and from the collection of the CBS, Baarn the Netherlands were compared, using micro-gel electrophoresis. Both species are reported for the first time as pathogens of raspberry in Bulgaria. This is only the second report in phytopathological literature ofP. citrophthora on raspberry, the first being from Chile [Latorre and Munoz, 1993]. 相似文献
13.
A. E. Kalamarakis V. P. Demopoulos B. N. Ziogas S. G. Georgopoulos 《European journal of plant pathology / European Foundation for Plant Pathology》1989,95(Z1):109-120
Mutants ofNectria haematococca var.cucurbitae with high resistance to triadimenol could be isolated at high frequency. Resistance of 30 such mutants studied, was due to a mutation at thetri-1 locus, that maps in linkage group I, 10 cross-over units from the mating type locus. Thetri-1 mutation has no obvious effects on growth and sporulation on media without fungicide and on virulence for squash seedlings and mature fruit. In addition, a resistant mutant killed all of artificially inoculated seedlings in the presence of triadimenol at a concentration which gave 100% protection against the original wild type strain. Thetri-1 mutants were crossresistant at various levels to triadimefon, bitertanol, and propiconazol, but not to non-triazole SBIs. Their sensitivity to three imidazole derivatives was even higher than that of the wild type strains. This is believed to be the first report of a major gene for resistance to an SBI fungicide.Isolatie vanNectria haematococca var.cucurbitae mutanten met een hoog niveau van resistentie tegen triadimenol bleek zeer gemakkelijk. Uit genetische analyse van 30 van deze mutanten bleek dat in alle een mutatie voorkwam in de tri-1 locus die kon worden gelokaliseerd op koppelingsgroep I, 10 overkruisingseenheden verwijderd van de mating-type locus. Detri-1 mutatie had geen waarneembare effecten op groei en sporulering van de schimmel op fungicide-vrij medium en op pathogeniteit ten aanzien van zaailingen en rijpe vruchten van pompoen.Triadimenol-behandeling van zaailingen bleek aantasting door de resistente mutant niet te kunnen voorkomen, terwijl behandeling wel effectief bleek tegen de ouderstam. 相似文献
14.
Séverine Cohen Valérie Allasia Paul Venard Sylvia Notter Christian Vernière Franck Panabières 《European journal of plant pathology / European Foundation for Plant Pathology》2003,109(8):791-805
Isolates of Phytophthora pathogenic to citrus crops on Eastern Corsica and associated with gummosis were identified by PCR-RFLP of internal transcribed spacers (ITS) sequences and characterized by the random amplified microsatellites (RAMS) technique. A sample of 114 isolates collected from diseased trunks and fruits, and from soil, were overwhelmingly Phytophthora citrophthora. Further analysis indicated that the P. citrophthora population was not homogeneous in citrus groves. There were two groups, with a few (4%) atypical isolates in two marginal groups. The major groups have been re-examined in the light of mating behaviour, RFLPs of mitochondrial DNA and sequence comparisons of ITS regions of rDNA. They were found distinct with all these criteria and perhaps constitute distinct taxa. The results indicate that important modifications occurred in the population structure of P. citrophthora over time in Corsican groves. These changes may have impact on the recent outbreaks of gummosis. 相似文献
15.
Thomas Thomidis 《Phytoparasitica》2002,30(2):191-193
The virulence ofPhytophthora citrophthora isolated from various host-plants on three peach rootstocks (GF677, PR204, KID I) was examined. There was no significant
difference among the rootstocks with respect to their susceptibility to testedP. citrophthora isolates. The most virulent isolate originated from sycamore (Acer pseudoplatanus); isolates from pistachio trees (Pistacia vera) also showed high virulence but were significantly less virulent than the sycamore isolate. Isolates originating from plum
(Prunus domestica), almond (Prunus amygdalus) and lemon (Citrus limon) trees were moderately virulent on peach rootstocks; those from cyclamen (Cyclamen persicum) showed the lowest virulence of those tested. There was thus great variation in virulence among the testedP. citrophthora isolates. It is possible that the isolates ofP. citrophthora from sycamore, pistachio, plum, almond and lemon trees are a threat to peach trees, whereas the low virulence of the isolates
from cyclamen hosts suggests that these pathogens are not a serious threat to peach trees.
http://www.phytoparasitica.org posting Jan. 3, 2002. 相似文献
16.
Luis Armando Alvarez Maela León Paloma Abad-Campos José García-Jiménez Antonio Vicent 《European journal of plant pathology / European Foundation for Plant Pathology》2011,129(1):103-117
Considerable tree losses have been observed during the past few years in Spain due to Phytophthora branch canker of clementines
caused by Phytophthora citrophthora. The emergence of this disease led to the speculation that either the pathogen has evolved increasing its aggressiveness
or specificity to clementines. A total of 134 isolates of P. citrophthora collected from 2003 to 2005 in 135 citrus orchards in Spain and 22 reference isolates were analyzed genotypically and phenotypically
to determine the structure of the population. Genotypic diversity was evaluated by means of Inter-Simple Sequence Repeat (ISSR)
markers. Among the phenotypic characteristics examined, sporangial characters, sexual behavior, growth rates and colony morphology
of the isolates at different temperatures were studied. The aggressiveness and host-specificity of selected isolates were
evaluated by pathogenicity tests on sweet oranges and clementines under field conditions. Phytophthora branch canker of clementines
was associated mainly with one genotype (P-1), which included 88% of the isolates obtained from branches. Strains isolated
years before the first disease outbreak clustered also with this major genotype, thus it may be considered as a predominant
population. Thirteen other minor genotypes were determined, but most contained only one isolate. Although there was wide variation
in the morphological and physiological characters, all Phytophthora isolates obtained from branch cankers were sexually sterile
and showed a characteristic petalloid colony pattern. As in previous greenhouse studies, pathogenicity tests under field conditions
demonstrated that clementines and their hybrids were more susceptible to P. citrophthora than sweet oranges. However, no evidence was found to support the hypothesis that the emergence of the disease was associated
with more aggressive or host-specific forms of P. citrophthora. 相似文献
17.
Effects of irrigation on the dynamics of soil populations of Phytophthora citrophthora have been studied in three citrus orchards in East Sicily (Italy). Significant increases of inoculum levels were detected 24 h after irrigation. In one orchard throughout summer, population of P. citrophthora beneath the tree canopy was more than 15 propagules g-1 soil, a value which is considered a threshold level for root rot infections. 相似文献
18.
Yuuri Hirooka Takao Kobayashi Jun Takeuchi Tsuyoshi Ono Yasunori Ono Keiko T. Natsuaki 《Journal of General Plant Pathology》2007,73(5):330-335
A ring spot disease of Aloe vera was found on leaves of potted seedlings of Aloe vera in Hachijojima and Chichijima Islands, Tokyo. From tissue of ring spot lesions, a fungus producing Fusarium-type conidia was consistently isolated. After 1 month, reddish perithecia of nectriaceous fungus had formed on the colonies
of this isolate on PDA. These nectriaceous and Fusarium fungi were identified as Haematonectria haematococca and Fusarium sp., respectively. From a single ascospore isolation, the former was confirmed to be the teleomorph of the Fusarium sp. Typical ring spot lesions were reproduced by artificial inoculations using single ascospore and single conidium isolates.
Inoculations of five species of genus Aloe revealed that they were highly susceptible except for A. arborescens. This is the first report of a disease on Aloe caused by H. haematococca (anamorph: Fusarium sp.) in Japan, and it was named aloe ring spot. 相似文献
19.
Danile Debieu Jocelyne Bach Alexandrine Lasseron Christian Malosse Pierre Leroux 《Pest management science》1998,54(2):157-167
The relative importance of the depletion of ergosterol versus the accumulation of precursor or abnormal sterols in the mechanism of fungal growth inhibition by sterol biosynthesis inhibitor fungicides is incompletely understood. In order to investigate this problem further, the degree of inhibition of the growth of Nectria haematococca by fungicides with different enzymatic targets in the sterol biosynthetic pathway was determined and compared with their effects on the sterol profile. The sensitivity of N. haematococca was highest towards fenpropimorph, followed by tebuconazole, terbinafine, fenpropidin and tridemorph. Terbinafine, a squalene epoxidase inhibitor, induced a very large accumulation of squalene without very significant inhibition of ergosterol biosynthesis and growth. The fungus appeared able to tolerate large amounts of squalene. In the case of tebuconazole, a sterol 14α-demethylase inhibitor, it seemed that the accumulation of C4 mono- and dimethyl sterols was responsible for fungitoxicity. Fenpropimorph and fenpropidin seemed to be good inhibitors of both sterol Δ14-reductase and Δ8→Δ7-isomerase, whereas tridemorph was a better inhibitor of Δ8→Δ7-isomerase than of the Δ14-reductase. Large accumulations of Δ8,14- or Δ8-sterols and correspondingly large decreases in the ergosterol content are both implicated in the fungitoxicity of these compounds in N. haematococca. © 1998 Society of Chemical Industry 相似文献
20.
Oranges and lemons infected with Phytophthora citrophthora and P. syringae were placed among healthy fruits in boxes kept at 5, 10 and 14°C. The spread of the rot by contact infection was assessed after 3,6,12 and 18 days and again after 7 days' shelf-life at 17°C. P. citrophthora infected adjacent fruits after 12 days at 10°C and 3 days at 14°C. No infection occurred at 5°C. P. syringue infected the fruits at all the temperatures tested. On fruits kept for 6 days at 5°C, the rot developed after shelf-life. The presence of Phytophthora-infected fruits in orange and lemon packing boxes enhanced the development of penicillium rots. Post-harvest dips in metalaxyl at 0.05 and 0.1% concentrations and fosetyl-Al at 0.1,0.2 and 0.3% concentrations prevented the spread of P. citrophthora in packing boxes kept for 30,40 and 60 days at 11°C, but had no effect on penicillium rots. The mixture of the above fungicides with thiabendazole at 0.1%] or imazalil at 0.05%, concentrations gave best control against phytophthora and penicillium rots. 相似文献