共查询到20条相似文献，搜索用时 15 毫秒
1.
J.H.M. Schneider C.G. Kocks M.T. Schilder 《European journal of plant pathology / European Foundation for Plant Pathology》2001,107(7):723-738
looseness-1In two observation fields, where six sites were artificially infested with Rhizoctonia solani AG 2-t, bare patches developed. These patches did not re-occur at the site of infestation in three successive years. In fields with and without artificial infestation, natural infection of tulip bulbs by Rhizoctonia spp. occurred. The spatial distribution of infected tulip bulbs was visualised in maps after kriging. The influence of sampling intensity was evaluated by stepwise reduction obtained in the observed data set of the first year. Omnidirectional semivariogram characteristics did not change when sampling intensity was reduced down to 10%. The average maximum prediction error was minimised at sampling intensities varying from 7% to 25%. Naturally occurring bare patches slowly vanished during successive cropping of flower bulbs and did not re-appear in the fourth growing season. A high frequency of isolation of R. solani AG 2-t in one field (Lisse-2) in the fourth consecutive crop did not result in bare patches in that year. It is hypothesised that a reduction in aggressiveness may account for this observation. In contrast, bulb rot due to Rhizoctonia spp. increased during the observation period. R. solani AG 5 isolates were seldom isolated before the bulbs flowered, but were the dominant isolate from bulbs at harvest. In a growth chamber experiment, it was demonstrated that AG 5 did not account for replacement of AG 2-t. However, it was demonstrated that competition may partially explain replacement of AG 2-t isolates during the growing season. At 18 °C, but not at 9 °C, an AG 4 isolate prevented AG 2-t colonising and infecting iris bulbs when both isolates were introduced together to soil. Rhizoctonia populations develop in relation to soil temperature and plant development. It is hypothesised that a temporal niche differentiation may be one of the mechanisms affecting the dynamics of rhizoctonia bare patch of tulips. 相似文献
2.
J.H.M. Schneider M.T. Schilder G. Dijst 《European journal of plant pathology / European Foundation for Plant Pathology》1997,103(3):265-279
During a spring survey in 1991, 130 isolates of R. solani were collected in 25 commercial flower bulb fields from diseased plants occurring in bare patches. On the basis of hyphal fusion frequency and pathogenicity to flower bulbs, tulip isolates were provisionally assigned to AG 2-t to distinguish these isolates from AG 2-1 isolates which were non-pathogenic to bulbs. Hyphal fusion frequency of a subgroup of 7 AG 2-t isolates was highly variable when paired with 7 AG 2-1 isolates (2-75%), thus making assignment of AG 2-t isolates to AG 2-1 inconclusive. The mean hyphal fusion frequency among AG 2-t isolates was 65% (±6%) indicating AG 2-t to be a relatively homogeneous group. Hyphal fusion frequency among AG 2-1 isolates was highly variable with a mean 51% (±25%) indicating AG 2-1 to be a heterogeneous group. The optimum growth temperature for AG 2-t and AG 2-1 isolates on malt peptone agar was 20-25 °C. The host range of AG 2-t and two AG 2-1 isolates comprised tulip, iris, hyacinth and lily at both 9 and 18 °C, and cruciferous, sugarbeet and lettuce seedlings at 18 °C. Six other AG 2-1 isolates were pathogenic to cruciferous seedlings, but not to any of the bulbous crops. The tested narcissus, Tagetes patula, tomato, potato, wheat, leek and maize cultivars were not susceptible to AG 2-t and AG 2-1 isolates. Statistical analysis using a proportional-odds model revealed significant differences in aggressiveness between R. solani AG 2-t isolates and differences in susceptibility between tulip and iris cultivars. At 18 °C, but not at 9 °C, isolates representing AG 2-2, AG 4, AG 5 and AG BI were pathogenic to bulbous crops. In addition to bare patch causing AG 2-t isolates, other anastomosis groups may cause disease in field grown tulips. For the development of optimal crop rotation schedules, the impact of bulb rot causing isolates under field conditions needs further study. 相似文献
3.
Ricardo B. Baldassari Ester Wickert Antonio de Goes 《European journal of plant pathology / European Foundation for Plant Pathology》2008,120(2):103-110
In the present study, the pathogenicity of 36 isolates of Guignardia species isolated from asymptomatic ‘Tahiti’ acid lime fruit peels and leaves, ‘Pêra-Rio’ sweet orange leaves and fruit peel
lesions, and a banana leaf were characterized. For pathogenicity testing, discs of citrus leaves colonized by Phyllosticta citricarpa under controlled laboratory conditions were kept in contact with the peels of fruit that were in susceptible states. In addition,
pathogenicity was related to morphological characteristics of colonies on oatmeal (OA) and potato dextrose agar (PDA). This
allowed the morphological differentiation between G. citricarpa and G. mangiferae. Polymerase chain reactions (PCRs) were also used to identify non-pathogenic isolates based on primers specific to G. citricarpa. A total of 14 pathogenic isolates were detected during pathogenicity tests. Five of these were obtained from leaf and fruit
tissues of the ‘Tahiti’, which until this time had been considered resistant to the pathogen. Given that the G. citricarpa obtained from this host was pathogenic, it would be more appropriate to use the term insensitive rather than resistant to
categorize G. citricarpa. A non-pathogenic isolate was obtained from lesions characteristic of citrus black spot (CBS), indicating that isolation
of Guignardia spp. under these conditions does not necessarily imply isolation of pathogenic strains. This also applied to Guignardia spp. isolates from asymptomatic citrus tissues. Using fluorescent amplified fragment length polymorphism (fAFLP) markers,
typically pathogenic isolates were shown to be more closely related to one another than to the non-pathogenic forms, indicating
that the non-pathogenic isolates display higher levels of genetic diversity. 相似文献
4.
Thirty-four isolates ofFusarium oxysporum f.sp.melonis (F.o.m.) obtained from 205 fields in melon-producing areas in the southeastern Anatolia Region of Turkey were identified on the basis
of colony morphology and pathogenicity by the root dip method. In this region the mean prevalence of wilt disease was 88.1%
and the mean incidence of disease was 47.5%. Physiologic races 0, 1, 2, and 1,2 of the pathogen were determined by their reactions
on differential melon cultivars ‘Charentais T,’ ‘Isoblon’, ‘Isovac’ and ‘Margot’ in the greenhouse. Race 1,2, representating
58.8% (20/34) of all isolates, was widely distributed. Of the other pathogenic isolates, eight were identified as race 0,
five as race 1, and one as race 2. This is the first report of physiologic races ofF.o.m. in Turkey. Of 44 melon cultivars tested in the greenhouse for resistance toF.o.m. races, 36 were found to be moderately resistant to race 0, 17 were susceptible to race 1,2, 34.1% were highly resistant to
race 1, and 52.2% had moderate resistance to race 2.
http://www.phytoparasitica.org posting July 16, 2002. 相似文献
5.
In the course of pre- and postharvest epidemiological studies on bulbs contamination byAspergillus niger, two Sudanese onion cultivars were tested: ‘Saggai Red’ and ‘El-Hilo White’.A. niger spores, whether seedborne, soilborne or airborne, were avirulent to the healthy growing onion plants. The fungus heavily
contaminated the dead onion tissues, mainly the dead leaves followed by the dry scales, the dead roots and, to a lesser extent,
the bulb necks, preferring the red-skinned cultivar to the white one. The initial spores carried from naturally contaminated
field soil on the dead tissues could germinate and produce massive numbers of new spores on bulbs stored at average climatic
conditions of Sudan (23–39°C, 29–93% relative humidity). Under laboratory-controlled conditions, optimal growth occurred at
75–85% r.h. on bulbs with dry scales and maximum losses occurred at 100% r.h. and ambient temperature. Underin vitro conditions, the optimal growth and sporulation temperature forA. niger was in the range of 30–35°C. Early harvesting and removal of the dead onion tissues improved bulb storability in aseptic
stores under low temperature and relative humidity conditions.
http://www.phytoparasitica.org posting Oct. 20, 2003. 相似文献
6.
Marie-Agnès Jacques Nathaëlle Luçon Sandrine Houdault 《European journal of plant pathology / European Foundation for Plant Pathology》2009,124(4):695-700
Bacterial blight of garlic, caused by Pseudomonas salomonii, results in leaf and sheath necrosis and sometimes leads to soft rot and plant death. The epidemiology of this bacterial
disease, known as ‘Café au lait’ disease, is poorly understood and no resistant cultivars are currently available. To develop
control strategies for this disease, we investigated principal sources of inoculum. The pathogen was isolated from bulbs from
plants with typical vegetative symptoms of bacterial blight. Subsequent development of typical foliar symptoms on plantlets
originating from symptomatic bulbs demonstrated transmission of the pathogen in the planting material. In one of three field
experiments the contamination rate of planting stock influenced the disease incidence in field-grown garlic. The importance
of planting stock as a source of inoculum was demonstrated here and should be evaluated relative to other potential sources
such as crop debris, soil or alternate hosts in order to develop successful control strategies. 相似文献
7.
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
8.
Single-ascospore-derived isolates ofMycosphaerella fijiensis Morelet from false horn ‘Agbagba’ plantain leaves obtained from five different villages in southern Nigeria were stimulated
to mate under artificial conditions. Pairs of isolates were incubated under blacklight on potato dextrose agar (PDA) with
surface-sterilized plantain leaves or on PDA with autoclaved plantain leaves. Some isolates were observed to be sexually compatible
by their ability to produce spherical to bulb-shaped fruiting body structures (FBS) and ascospores on pairing. FBS were observed
to measure between 39–65 μm (smallest diameter) and 39–104 μm (largest diameter; mean 55.3×71.1 μm) in diameter, whereas ascospore
lengths measured between 13.0 and 14.9 μm. Length of incubation time required for FBS production was dependent on the pair
of isolates involved, the average being 40.1 days. With some pairs, ascospores were observed after 35 days of incubation.
http://www.phytoparasitica.org posting Dec. 16, 2002. 相似文献
9.
Kazutaka Kido Rie Adachi Masaru Hasegawa Kazutaka Yano Yasufumi Hikichi Shigeharu Takeuchi Tae Atsuchi Yuichi Takikawa 《Journal of General Plant Pathology》2008,74(4):302-312
An internal fruit rot with a malodor was found in netted melons (Cucumis melo L.) in commercial greenhouses in Kochi Prefecture, Japan, in 1998, despite their healthy appearance and lack of water-soaking
or brown spots on the surface. A yellow bacterium was consistently isolated from the affected fruits. To confirm the pathogenicity
of eight representative isolates of the yellow bacterium, we stub-inoculated ovaries (immature-fruits) 5–7 days after artificial
pollination, with a pin smeared with bacteria. After the melon fruits had grown for 60 more days, an internal fruit rot resembling
the natural infection appeared, and the inoculated bacterium was reisolated. The melon isolates had properties identical with
Pantoea ananatis, such as gram-negative staining, facultative anaerobic growth, indole production, phenylalanine deaminase absence, and acid
production from melibiose, sorbitol, glycerol, and inositol. Phylogenetic analysis based on 16S rDNA sequences showed that
the melon bacterium positioned closely with known P. ananatis strains. The melon bacterium had indole acetic acid (IAA) biosynthesis genes (iaaM and iaaH) and a cytokinin biosynthesis gene (etz). The bacterium could be distinguished from the other ‘Pantoea’ group strains by rep-PCR genomic fingerprinting. From these results, the causal agent of internal fruit rot was identified
as a strain of P.ananatis [Serrano in (Philipp J Sci 36:271–305, 1928); Mergaert et al. in (Int J Syst Bacteriol 43:162–173, 1993)].
The nucleotide sequence data reported are available in the DDBJ database under accessions AB297969, AB373739, AB373740, AB373741,
AB373742, AB373743 and AB373744. 相似文献
10.
Greenhouse and field evaluations of onion for resistance to Fusarium basal rot caused byFusarium oxysporum f.sp.cepae were conducted on cultivars ‘Akgün 12’ and ‘Rossa Savonese’ previously described as resistant at the seedling stage. In the
greenhouse experiments inoculations were carried out on seeds or soil; in the field experiments evaluation was performed on
onion sets from plants grown in naturally infested soils. Akgün 12 and to a lesser extent Rossa Savonese were resistant to
the disease at the bulb stage in all experiments. Results were also consistent with those obtained from a previous screening
at the seedling stage. Onion sets were also extracted and fractionated by thin layer chromatography to determine their content
of antifungal compounds. Extracts were characterized by the expression of distinct antifungal components, which may be involved
in resistance to the pathogen.
http://www.phytoparasitica.org posting July 14, 2004. 相似文献
11.
Nihal Özder 《Phytoparasitica》2002,30(4):434-436
Nymphal development time and fecundity ofSitobion avenae (F.) (Homoptera: Aphididae) were determined on nine widespread wheat varieties cultivated in Tekirdağ Region in Turkey. Tests
were carried out in controlled environment chambers (25±1°C, 65±5% r.h.; 16:8, L:D). Development time (±S.E.) ranged from
5.75±0.25 to 7.20±0.20 days. Fecundity per female ofS. avenae was found to be the highest (12.87±1.50) on wheat cv. ‘Sana’. In this investigation cvs. ‘MV-17’, ‘Miryana’, ‘Pehlivan’ and
‘Saraybosna’ were particularly resistant againstS. avenae.
http://www.phytoparasitica.org posting July 8, 2002. 相似文献
12.
B. H. H. Bergman 《European journal of plant pathology / European Foundation for Plant Pathology》1966,72(3-6):222-230
In field infections of tulip bulbs caused byF. oxysporum, soil temperature, although important, has been proved to be not the decisive factor influencing the moment of infection. The presence in the white skin tissue of young bulbs of a water soluble substance which has a growth inhibiting effect onF. oxysporum in vitro has been demonstrated. Inoculations with the fungus on the white skins were unsuccessful. In the susceptible tulip cultivar so far examined the concentration of this substance in extracts decreases during the last weeks before the bulbs mature. It is suggested that this substance is protecting the susceptible fleshy bulb scales during the greater part of the growth period and that its diminution during the final weeks enablesF. oxysporum to infect the scales during this period. 相似文献
13.
Field experiments were conducted during 1997 and 1998 to determine the effects of sugar beet cultivar susceptibility to Cercospora
leaf-spot on the sensitivity ofCercospora beticola isolates to the triazole fungicide flutriafol. Four cultivars with different levels of disease resistance were treated in
experimental plots with six spray applications of flutriafol. Disease assessments were carried out at 15-day intervals. Sensitivity
to flutriafol was measured on isolates collected from the plots ∼15 days after the last flutriafol application. Measurements
of disease severity and calculations of AUDPC (area under disease progress curve) values showed a distinct differentiation
among cultivars, reflecting their level of disease resistance. Disease severity was significantly lower in cvs. ‘Bianca’ and
‘Areth’ than in ‘Univers’ and ‘Rizor’ both in the untreated and in the flutriafol-treated plots. Fungal isolates from flutriafol-treated
plots were less sensitive to the fungicide than were isolates from untreated plots. However, no differences in isolate sensitivity
were observed among the cultivars, as regards their level of disease resistance. Despite the fact that the use of resistant
cultivars cannot eliminate selectively the resistant strains, it can eliminate both resistant and sensitive isolates. Reducing
the number of treatments with DMIs, by applying them only when environmental conditions are favorable for disease development,
is a prerequisite for successful resistance management; therefore, the use of disease-resistant varieties could aid toward
management of DMIs resistance inC. beticola.
http://www.phytoparasitica.org posting May 6, 2003. 相似文献
14.
T. Abou Al Fadil G. Dechamp-Guillaume R. Darvishzadeh A. Sarrafi 《European journal of plant pathology / European Foundation for Plant Pathology》2007,117(4):341-346
Phoma macdonaldii is one of the most important pathogens of sunflower (Heliantus annuus) in France. In order to determine the inheritance of resistance to the disease, five sunflower genotypes with wide genetic
variability for resistance to two ‘collar’ and two ‘root’ Phoma isolates were crossed in a diallel programme. Four separate
experiments were undertaken under controlled conditions. In each one, the response of parental genotypes and their F1 hybrids
were evaluated with one of the four Phoma isolates. Analysis of variance was performed to determine the effects of genotype
on disease severity score when inoculated with ‘collar’ or ‘root’ Phoma isolates and showed significant variability among
parents and F1 hybrids for disease severity score. Diallel analysis showed that general combining ability (GCA) and specific
combining ability (SCA) effects for resistance to ‘collar’ and ‘root’ Phoma isolates were highly significant for each of the
four isolates indicating that both kinds of gene effects were important in controlling the resistance. The GCA/SCA ratios
were more than one for three out of four isolates showing that additive genetic effects were more important than non-additive
effects for resistance to three of the studied Phoma isolates. Hence, conventional breeding methods could be recommended to
achieve genetic improvement to such ‘collar’ and ‘root’ Phoma isolates. 相似文献
15.
Eleven soybean cultivars with different levels of susceptibility to virulent isolate SG915 ofCalonectria ilicicola were examined for reaction to metabolites produced by the isolate. When the culture filtrate from isolate SG915 was applied
to trifoliates from 11 cultivars, cvs. ‘Cajun’ and ‘Asgrow 7986’ exhibited reduced wilting severity. However, there was no
correlation between sensitivity to culture filtrate and susceptibility to the fungal isolate. Wilting severity on cv. ‘Riverside
699’ was greatest when trifoliates were treated with culture filtrates from isolates SG915 (highly virulent) and C31 (less
virulent). The dilution end-point for culture filtrates of virulent isolate SG915 was determined to be 1:8. Nonautoclaved
culture filtrates caused complete wilt of soybean trifoliates after 36 h, but autoclaved culture filtrates demonstrated a
reduced ability to wilt leaves. Electrolyte leakage from treated leaf tissues increased over time regardless of the concentrations
of culture filtrate tested. The greatest electrolyte losses were observed during the initial 30 min incubation of leaf tissues.
The highest concentration of culture filtrate (50%, v/v) induced more electrolyte loss than the low concentration (10%, v/v)
or control. These results suggest that toxic metabolites ofC. ilicicola may be involved in disease development with leaf symptom expression. 相似文献
16.
17.
A. H. PRESLY 《Plant pathology》1985,34(3):422-427
Botrytis byssoidea (mycelial neck rot) was more prevalent than B. allii (sclerotial neck rot) on the leaves of field onions and the bulbs of stored onions grown in some of the areas where onions or onions and leeks had previously been grown sequentially.
B. byssoidea and B. porri were also isolated from leeks. Spores of B. allii, B. byssoidea (from onions and leeks), B. porri , and B. squamosa caused infection of seedlings of salad (green) and bulb onions.
Inoculation with B. squamosa spores caused severe infection of seedling leaves, but inoculation with mycelial discs caused little damage to onion bulb tissue. By comparison, mycelial discs of the remaining species were highly pathogenic to bulbs.
The practical implications of disease transfer of certain of these species between onions and leeks are discussed. 相似文献
B. byssoidea and B. porri were also isolated from leeks. Spores of B. allii, B. byssoidea (from onions and leeks), B. porri , and B. squamosa caused infection of seedlings of salad (green) and bulb onions.
Inoculation with B. squamosa spores caused severe infection of seedling leaves, but inoculation with mycelial discs caused little damage to onion bulb tissue. By comparison, mycelial discs of the remaining species were highly pathogenic to bulbs.
The practical implications of disease transfer of certain of these species between onions and leeks are discussed. 相似文献
18.
Three isolates of Chrysanthemum stem necrosis virus (CSNV) were obtained from chrysanthemum plants in distinct regions of Japan in 2006 and 2007. All the original host plants
showed severe necrotic symptoms on the leaves and stems. Amino acid sequence data of the nucleocapsid protein genes of the
three isolates (CbCh07A, TcCh07A, and GnCh07S) showed high identities with those of two other CSNV isolates, HiCh06A L1 from
Japan and Chry1 from Brazil. Furthermore, for the first time the complete nucleotide sequence of the S RNA was determined
for CSNV (isolate HiCh06A). In phylogenetic analysis based on the non-structural protein genes from the genus Tospovirus, HiCh06A L1 was placed in the same genetic group as Tomato spotted wilt virus (TSWV) and Impatiens necrotic spot virus. Host range examination for isolates HiCh06A L1 and CbCh07A showed that green pepper (cv. ‘Kyoyutaka’, ‘Saitamawase’, ‘Tosakatsura’,
‘L3 sarara’ and ‘L3 miogi’) and tomato (cv. ‘Sekaiichitomato’) were systemically susceptible hosts, whereas TSWV-resistant
Solanaceae species, Capsicum chinense, Lycopersicon peruvianum and a TSWV-resistant cultivar of green pepper (cv. TSR miogi), were resistant. 相似文献
19.
Dean K. Malvick Niklaus J. Grünwald Alan T. Dyer 《European journal of plant pathology / European Foundation for Plant Pathology》2009,123(2):171-182
Aphanomyces euteiches (races 1 and 2) causes root rot of alfalfa; however, its population biology and distribution are poorly understood where
alfalfa is a major crop. The objectives of this study were to (1) characterise the distribution and frequency of races of
A. euteiches in Illinois alfalfa fields, (2) determine host range of A. euteiches on cultivated and native legumes, and (iii) to describe genetic diversity and population genetic structure of A. euteiches in alfalfa fields. To accomplish this, soil samples (n = 103) were collected from 30 alfalfa fields in 18 Illinois counties. Using the susceptible cv. ‘Saranac’, 148 isolates of
A. euteiches were baited from the soil. The virulence phenotype of isolates representing all 18 counties was tested, and 54% were R1 and
46% were R2. Both races were detected in 61% of the counties, whereas only R1 was detected in 22% and R2 in 17%. Thirteen
legume hosts for isolates from alfalfa fields were identified based on symptoms and/or production of oospores in roots. In
addition to six previously known hosts, seven species were susceptible to infection: kura clover, purple prairie clover, white
prairie clover, ladino clover, hairy vetch, Canadian milk vetch, and Illinois tick trefoil. AFLP analysis revealed high levels
of genetic diversity among the isolates from different fields and counties and a lack of genetic structuring of populations
based on race or geographical origin. The results suggest that populations of A. euteiches in alfalfa fields are diverse, often composed of races 1 and 2, and create risk for alfalfa and to multiple cultivated and
native legume species. 相似文献
20.
Two distinct races ofDitylenchus dipsaci in Israel were identified: one, which infects and damages onion and garlic, reproduces on pea, but does not infect phalaris
grass; and a second, which infects and damages phalaris—and, probably, also ‘Saia’ oats—but fails to infect onion and garlic.
A new ‘garlic’ race of the nematode does not appear to have been introduced into Israel together with the ‘Lavinia’ garlic
cultivar, as previously speculated, but rather the introduced Lavinia clone is highly susceptible to the existing ‘onion and
garlic’ race ofD. dipsaci. 相似文献