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1.
Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most destructive wheat diseases in China. Yunnan Province, located in south-western China, possesses unique
features of geography, climate, wheat growth and stripe rust epidemics, different from main epidemic regions in China. The
isolates of this pathogen were collected from nine counties in Yunnan Province during February to May of 2008. Used as a comparison,
isolates were also collected from five counties of Gansu Province, the province important in inter-regional stripe rust epidemics
in China. Amplified fragment length polymorphism (AFLP) method was applied to study the population genetics of the pathogen
among different populations in these two provinces. Forty one AFLP genotypes were obtained from 150 isolates and the genotype
qj3 showed the highest frequency in Yunnan Province. While 22 genotypes were detected from 40 isolates, no genotype showing
as predominant was identified in Gansu Province. Genotypic diversity in Gansu Province was higher than that in Yunnan Province.
A free recombination signature was detected in Gansu Province but not in Yunnan Province. We concluded that the population
of P. striiformis in Yunnan Province can be considered as a clonal population. 相似文献
2.
Harsh Garg Linda M. Kohn M. Andrew Hua Li Krishnapillai Sivasithamparam M. J. Barbetti 《European journal of plant pathology / European Foundation for Plant Pathology》2010,126(3):305-315
Sclerotinia stem rot caused by Sclerotinia sclerotiorum is a serious threat to oilseed production in Australia. Eight isolates of S. sclerotiorum were collected from Mount Barker and Walkway regions of Western Australia in 2004. Comparisons of colony characteristics
on potato dextrose agar (PDA) as well as pathogenicity studies of these isolates were conducted on selected genotypes of Brassica napus and B. juncea. Three darkly-pigmented isolates (WW-1, WW-2 and WW-4) were identified and this is the first report of the occurrence of
such isolates in Australia. There was, however, no correlation between pigmentation or colony diameter on PDA with the pathogenicity
of different isolates of this pathogen as measured by diameter of cotyledon lesion on the host genotypes. Significant differences
were observed between different isolates (P ≤ 0.001) in two separate experiments in relation to pathogenicity. Differences were also observed between the different Brassica genotypes (P ≤ 0.001) in their responses to different isolates of S. sclerotiorum and there was also a significant host × pathogen interaction (P ≤ 0.001) in both experiments. Responses between the two experiments were significantly correlated in relation to diameter
of cotyledon lesions caused by selected isolates (r = 0.79; P < 0.001, n = 48). Responses of some genotypes (e.g., cv. Charlton) were relatively consistent irrespective of the isolates of the pathogen
tested, whereas highly variable responses were observed in some other genotypes (e.g., Zhongyou-ang No. 4, Purler) against
the same isolates. Results indicate that, ideally, more than one S. sclerotiorum isolate should be included in any screening programme to identify host resistance. Unique genotypes which show relatively
consistent resistant reactions (e.g., cv. Charlton) across different isolates are the best for commercial exploitation of
this resistance in oilseed Brassica breeding programmes. 相似文献
3.
Xiaojie Wang Wenming Zheng Heinrich Buchenauer Jie Zhao Qingmei Han Lili Huang Zhensheng Kang 《European journal of plant pathology / European Foundation for Plant Pathology》2008,120(3):241-247
Stripe rust of wheat caused by Puccinia striiformis f. sp. tritici is one of the most important diseases on wheat worldwide, especially in temperate regions with cool moist weather conditions.
A rapid and reliable detection of the pathogen in latent infected wheat leaves during overwintering of the fungus in the dormant
stage will contribute to determine the initial inoculum potential and thus to predict early outbreak and to improve effective
management of the disease. To achieve this aim, a PCR-based method was developed for specific and sensitive detection of P. striiformis. Specific primers were designed according to a genome-specific sequence of P. striiformis. To evaluate the specificity of the primers, seven different isolates and races of P. striiformis as well as six other pathogens of wheat were tested. All isolates of P. striiformis yielded a distinct band of a fragment of 470 bp, while using DNA of the other wheat pathogens as a template no amplification
product was detected. The sensitivity of the primers was tested using serial dilutions of total DNA from P. striiformis; the limit of detection was 10 pg of DNA. Using extracts from P. striiformis-infected wheat leaves, the fungus could be determined in the leaves before symptoms appeared. The stripe rust could also
be detected in the dormant stage by the PCR assay in samples of wheat leaves taken during the winter season. The application
of the PCR assay may be useful for rapid and reliable detection of P. striiformis in latent infected leaves of overwintering wheat plants. 相似文献
4.
Toyozo Sato Jun Okamoto Yosuke Degawa Shigeru Matsunari Kokichi Takahashi Keisuke Tomioka 《Journal of General Plant Pathology》2009,75(1):46-51
In some areas of Japan, yellow spots with white pustules on leaves, stems, petioles, peduncles and calyces were found on Ipomoea nil, I. triloba, I. lacunosa and I. hederacea var. integriuscula. We demonstrated that the diseases on I. nil, I. triloba and I. lacunosa were caused by host-specific strains of Albugo ipomoeae-panduratae and defined three forma speciales of the fungus, respectively, for the three Ipomoea species: “f. sp. nile”, “f. sp. trilobae” and “f. sp. lacunosae”. Because the diseases were new to Japan, we coined the Japanese name “shirosabi-byo”, which means white rust. We also showed
that the disease on I. hederacea var. integriuscula was caused by A. ipomoeae-hardwickii. We named this new disease “white rust (shirosabi-byo in Japanese)”. 相似文献
5.
Xueren Cao Xiayu Duan Yilin Zhou Yong Luo 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(4):525-535
Experiments were conducted for 3 seasons, 2007–2008, 2008–2009 and 2009–2010 in a wheat field planted with a cultivar susceptible
to powdery mildew in Langfang City, Hebei Province, China. Plants were inoculated with Blumeria graminis f. sp. tritici (Bgt) and conidia of Bgt in the air were trapped using volumetric spore samplers. Disease severity was recorded weekly. The relationships between
airborne conidial concentrations and meteorological factors, as well as disease index were analyzed. Conidia were first detected
about 20 days after inoculation in all three seasons, and then increased gradually with time. The highest conidial concentrations
in the air were observed in mid-May 2008 and 2009 and late May 2010 at growth stage (GS) 10.5.4. The concentrations of Bgt conidia after inoculation (GS 5) to milky ripe (GS 11.1) in the air were positively correlated with temperature, solar radiation,
and negatively with relative humidity and vapor pressure deficit (VPD). Prediction models of Bgt conidial concentrations in the air based on meteorological factors were constructed using multiple regression analysis. Time
series analysis, using autoregressive integrated moving average (ARIMA) (p, d, q) models, showed that each of the three season’s
data can be fitted with simple ARIMA (1, 0, 0) models. Conidial concentrations within the canopy were significantly higher
than those above the canopy (P < 0.01). The weekly-accumulated mean hourly conidia per cubic metre of air significantly (P < 0.01) correlated with disease index in all three seasons. 相似文献
6.
Samuel M. Imathiu Rumiana V. Ray Matthew Back Martin C. Hare Simon G. Edwards 《European journal of plant pathology / European Foundation for Plant Pathology》2009,124(1):117-126
In vitro detached leaf assays involving artificial inoculation of wounded and unwounded oat and wheat leaves were used to investigate
the potential pathogenicity and aggressiveness of F. langsethiae, which was linked recently to the production of type A trichothecenes, HT-2 and T-2 in cereals in Europe. In the first two
experiments, two assays compared disease development by F. langsethiae with known fusarium head blight pathogen species each used as a composited inoculum (mixture of isolates) at 10°C and 20°C
and found all fungal species to be pathogenic to oat and wheat leaves in the wounded leaf assay. In the unwounded leaf assay,
F. langsethiae was not pathogenic to wheat leaves. Furthermore, there were highly significant differences in the aggressiveness of pathogens
as measured by lesion length (P < 0.001). In the second two experiments, pathogenicity of individual F. langsethiae isolates previously used in the composite inoculum was investigated on three oat and three wheat varieties. The wounded leaf
assay showed that all isolates were pathogenic to all oat and wheat varieties but only pathogenic towards oat varieties in
the unwounded assay. Highly significant differences (P < 0.001) in lesion length were found between cereal varieties as well as between isolates in the wounded assay. Significant
differences in lesion lengths (P = 0.014) were also observed between isolates in the unwounded assay. Results from the detached leaf assays suggest that F. langsethiae is a pathogen of wheat and oats and may have developed some host preference towards oats. 相似文献
7.
The apple rust mite Aculus schlechtendali (Nal.) (Acari: Eriophyidae), is a main pest in apple-growing areas in Ankara, Turkey, and chemical control applications have
some limitations. Entomopathogenic fungi have a potential for biological control of mites. In this study, an entomopathogenic
fungus, Paecilomyces lilacinus (Thom) Samson (Deuteromycota: Hyphomycetes), was first isolated from the mite cadavers on Japanese crab apple leaves and
pathogenicity of the fungus was observed in different inoculum densities and relative humidities. The pathogen caused up to
98.22% mortality of the mite population. The effects of some fungicides on the entomopathogenic fungus were determined in
in vitro studies. Carbendazim, penconazole and tebuconazole were the most effective fungicides on mycelial growth of P. lilacinus, with EC50 values under 3 μg ml−1. In spore germination tests, captan, mancozeb, propineb were the most effective fungicides, followed by tebuconazole, penconazole,
nuarimol and chlorothalonil. Sulphur could not inhibit the conidia germination totally at 5,000 μg ml−1. Copper oxychloride and fosetyl-al prevented conidia formation at concentrations above 1,000 μg ml−1. 相似文献
8.
Stripe rust is considered as the current major rust disease affecting winter cereal production across the world. A quick, reliable PCR-based marker was developed here to detect, identify and rapidly monitor Puccinia striiformis f. sp. tritici (Pst) in wheat-growing areas. Three respective sets of primers, designed from β-tubulin, squalene monooxygenase and ketopantoate reductase genes selected from the full genome of Puccinia striiformis f. sp. tritici, amplified sequences of 239, 358 and 1518 bp, respectively, in Pst pathotypes. A fragment of 1518 bp unique to Pst pathotypes was amplified using primer set PstKeto F1_30/Pst KetoR1_1547 and distinguished the pathogen clearly from different Puccinia spp. and other fungal pathogens. The detection limit of the marker (KetoPstRA1500, accession no. KU240073) by conventional PCR assay was 10 pg. This marker could detect the pathogen in the host before symptom expression. The sensitivity and utility of the marker were further enhanced in a qPCR-based assay that was developed with a newly designed primer set PstKeto F1_1246/Pst KetoR1_1547, which amplified a product of 302 bp and detected as little as 10 fg of DNA. This PCR/qPCR based marker is suitable for studying cultivar resistance, which requires accurate quantification of the pathogen in diseased host tissue. 相似文献
9.
B. Wang C. L. Brubaker P. H. Thrall J. J. Burdon 《European journal of plant pathology / European Foundation for Plant Pathology》2010,128(4):541-551
Temporal variation in Fusarium oxysporum f. sp. vasinfectum (Fov) populations was determined by comparing the genetic diversity of pathogen isolates recovered from three consecutive cotton
crops (2002, 2004 and 2006) in the Boggabilla area of New South Wales, Australia. A total of 288 isolates were collected,
among which 25 distinct AFLP genotypes were identified. These genotypes were classified into two main groups corresponding
to known vegetative compatibility groups (VCG)—01111 and 01112. The Fov populations were dominated by four genotypes (I-A, I-B, II-A, II-B) that accounted for 87.5% of the isolates. Significant
temporal variation was observed in both sampled fields with 6.8% and 10.7% of total genetic variation being attributed to
differences among collections in different years. Genetic diversity based on Nei’s gene diversity and the Shannon-Wiener index
increased over time. Significant changes in the frequency of the dominant Fov genotypes were observed in one field, where genotype I-A declined from 84.8% to 40.0% over the study period (2002–2006),
while genotype I-B increased from 7.6% to 35.4%. Strong inter-genotype competition was detected in glasshouse bioassays with
93.4% of symptomatic plants sampled from dual inoculation trials being infected by single genotypes. Competition was differentially
mediated by cotton cultivars as the competitive ability of pathogen genotype I-B was enhanced on the resistant cultivar Sicot
189 relative to the susceptible cultivar Siokra 1–4. This suggests that host-mediated inter-genotype competition may play
an important role in temporal variation in Fov populations in the field. 相似文献
10.
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
11.
12.
Baidya N. Mahto Suraj Gurung Achala Nepal Tika B. Adhikari 《European journal of plant pathology / European Foundation for Plant Pathology》2012,133(2):405-417
Spot blotch, caused by Cochliobolus sativus (Ito & Kuribayashi) Drechs. ex Dastur, is one of the important diseases of wheat worldwide. The main objective of this study
was to investigate the phenotypic and genotypic variability among C. sativus isolates from the hills and plains in Nepal. A total of 48 monoconidial isolates of C. sativus from the hills (n = 24 isolates) and plains (n = 24 isolates) in Nepal were analyzed for morphology, aggressiveness and genetic structure. C. sativus isolates were grouped into three categories on the basis of their colony texture and mycelia colour. Thirteen isolates from
the hills and plains belonging to three morphological groups were randomly selected and evaluated for aggressiveness on eight
wheat cultivars (Chirya 1, Chirya 7, Milan/Shanghai 7, SW 89–5422, PBW 343, BL 1473, BL 3036, and RR 21) at the seedling stage.
Nonparametric analysis revealed that the isolates from the plains (median disease rating of 5) were significantly (P = 0.0001) more aggressive than the isolates from the hills (median disease rating of 3). A significant (P = 0.0001) isolate by cultivar interaction was demonstrated and the isolates from the same geographic region and morphological
group displayed different degrees of aggressiveness on wheat cultivars tested. Combined IS-PCR and rep-PCR analyses revealed
moderate gene diversity (H = 0.24 and 0.25 for the hills and plains, respectively). Low linkage disequilibrium (LD) value and non-significant (P = 0.001) population differentiation (G″ST = 0.05) were detected, indicating that isolates of C. sativus from the hills and plains in Nepal were genetically similar. Analysis of molecular variation (AMOVA) revealed low (7%) levels
of genetic variation between the hill and plain populations, whereas >93% of genetic variation was found within populations.
Overall, C. sativus isolates from Nepal are pathologically and genetically diverse, and such information will be useful in developing wheat cultivars
resistant to C. sativus. 相似文献
13.
Tong Liu Lixing Liu Xue Jiang Jumei Hou Kehe Fu Feihong Zhou Jie Chen 《European journal of plant pathology / European Foundation for Plant Pathology》2010,126(3):363-371
In order to explore the molecular mechanisms of virulence and genetic variance of Curvularia lunata in maize, an ATMT (Agrobacterium tumefaciens-mediated transformation) system was established in order to create a wide range of insertional transformants of C. lunata. Our results showed that the germinating conidia were the ideal starting material for transformation. Based on our optimised
transformation condition, the transformation efficiency of C. lunata with T-DNA was improved greatly, and the average transformation frequency was as high as 84 ± 5 transformants per 1 × 106 germlings. Southern blotting results of 39 randomly-selected transformants showed a unique hybridisation pattern and predominant
single-copy insertions. An ATMT library containing approximate 3000 transformants was generated, and four types of transformants
were screened in terms of growth rate, sporulation, mycelial pigmentation, and toxin production in vitro. This library will be used to identify genes involved in the virulence of the pathogen. 相似文献
14.
Lijie Ma Xiaoping Hu Xiangming Xu 《European journal of plant pathology / European Foundation for Plant Pathology》2017,147(3):713-716
Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is an important disease of wheat worldwide. Understanding the survival of Pst during the winter is critical for predicting Pst epidemics in the spring. We used a real-time quantitative PCR (qPCR) method to quantify Pst CYR32 biomass in infected wheat seedlings under several fluctuating temperature regimes (three average temperatures 0, ?5 and ?10 °C, each with two daily fluctuating amplitudes 8 and 13 °C). The survival of Pst CYR32 increased with increasing average temperature but also varied greatly with the amplitude – larger amplitude led to lower survival, particularly at 0 and ?5 °C. Nevertheless the survival at both amplitudes was still significantly greater than under the corresponding constant temperatures. There were small, albeit statistically significant, differences between the two cultivars (Xiaoyan 22, low winter-hardiness; Lantian 15, high winter-hardiness) in Pst CYR32 survival. This study indicated potential errors that could result from using daily average temperatures to predict Pst survival during the winter. 相似文献
15.
Lian Wu Xie Shu Mei Jiang Hong Hui Zhu Wei Sun Yong Chang Ouyang Shi Kun Dai Xiang Li 《European journal of plant pathology / European Foundation for Plant Pathology》2008,122(4):571-578
Sclerotinia sclerotiorum is a worldwide ascomycete fungal plant pathogen, which causes enormous yield losses on major economic crops such as crucifers,
grain legumes and several other plant families. The objective of this research was to isolate and characterise some bioactive
products from cultures of fungi associated with the marine sponge Axinella sp. In total, nine fungal isolates were obtained from the marine sponge Axinella sp. collected from the South China Sea. A group of test strains, including two G+ strains (Bacillus subtilis and Staphylococcus aureus), two G− strains (Escherichia coli and Pseudomonas aeruginosa) and three fungi including two plant pathogenic fungi Sclerotinia sclerotiorum and Magnaporthe grisea and Saccharomyces cerevisiae, were employed as the indicator organisms for bioactivity screening. Using antagonistic tests and bioactive screening of
the ethyl acetate (EtOAc) extracts of the corresponding cultures, fungal isolate JS9 showed the stronger efficacy against
the test indicator strains, especially the indicator fungal pathogens. Isolate JS9 was further identified as Myrothecium sp. by a combination of morphological features and 18S rDNA BLAST on GenBank. Two macrocyclic trichothecenes, roridin A (compound
1) and roridin D (compound 2) were purified by tracking the activity of the EtOAc extract fractions and characterised with
spectral analyses including MS, 1H-NMR, 13C-NMR and disortionless enhancement by polarization transfer (DEPT). In vitro antifungal tests showed that the two macrocyclic trichothecenes were bioactive against S. cerevisiae, M. grisea and S. sclerotiorum with minimal inhibitory concentrations of 31.25, 125 and 31.25 μg ml−1 for roridin A, and 62.5, 250 and 31.25 μg ml−1 for roridin D, respectively. The present investigation demonstrated that two antifungal trichothecenes including roridin
A and roridin D produced by the fungus Myrothecium sp. isolated from the marine sponge Axinella sp. could be potential inhibitors against the plant pathogen S. sclerotiorum.
Lian Wu Xie and Shu Mei Jiang contributed equally to this work. 相似文献
16.
Fusarium wilt is an economically important fungal disease of common eggplant (Solanum melongena) cultivated in the eastern Mediterranean region of Turkey. Seventy-four isolates of Fusarium oxysporum isolated from diseased eggplant displaying typical Fusarium wilt symptoms were screened for pathogenicity on the highly susceptible
cv. ‘Pala’. All the isolates tested were pathogenic to eggplant and designated as Fusarium oxysporum f. sp. melongenae (Fomg). Genetic diversity among a core set of 20 Fomg isolates that were selected based upon geographic locations, were characterized by using pathogenicity, vegetative compatibility
grouping (VCG), and random amplified polymorphic DNA (RAPD) analysis. The area under the disease progress curve (AUDPC) was
calculated for each Fomg isolate until 21 days after inoculation (DAI). The most virulent isolate was identified as Fomg10 based on AUDPC, disease severity and vascular discoloration measurements at 21 DAI. At this date, a good correlation was
observed between disease severity and AUDPC values for all isolates (r = 0.73). UPGMA (unweighted pair group method with arithmetic average) cluster analysis of RAPD data using Dice’s coefficient
of similarity differentiated all the Fomg isolates tested, and indicated considerable genetic variation among Fomg isolates, but isolates from the same geographic region were grouped together. There was no direct correlation between clustering
in the RAPD dendrogram and pathogenicity testing of Fomg isolates. Twenty isolates of Fomg were assigned to VCG 0320. 相似文献
17.
Daniela Minerdi Marino Moretti Yuan Li Laura Gaggero Angelo Garibaldi Maria Lodovica Gullino 《European journal of plant pathology / European Foundation for Plant Pathology》2008,122(2):227-237
A conventional PCR and a SYBR Green real-time PCR assays for the detection and quantification of Phytophthora cryptogea, an economically important pathogen, have been developed and tested. A conventional primer set (Cryp1 and Cryp2) was designed
from the Ypt1 gene of P. cryptogea. A 369 bp product was amplified on DNA from 17 isolates of P. cryptogea. No product was amplified on DNA from 34 other Phytophthora spp., water moulds, true fungi and bacteria. In addition, Cryp1/Cryp2 primers were successfully adapted to real-time PCR.
The conventional PCR and real-time PCR assays were compared. The PCR was able to detect the pathogen on naturally infected
gerbera plants and on symptomatic artificially infected plants collected 21 days after pathogen inoculation. The detection
limit was 5 × 103
P. cryptogea zoospores and 16 fg of DNA. Real-time PCR showed a detection limit 100 times lower (50 zoospores, 160 ag of DNA) and the
possibility of detecting the pathogen in symptomless artificially infected plants and in the re-circulating nutrient solution
of closed soilless cultivation systems. 相似文献
18.
Roghayeh Hemmati Mohammad Javan-Nikkhah Celeste C. Linde 《European journal of plant pathology / European Foundation for Plant Pathology》2009,125(4):617-628
The genetic structure of 276 Sclerotinia sclerotiorum isolates representing 37 field populations from four provinces in northern Iran were analysed with six polymorphic microsatellite
loci. In total, 80 haplotypes were detected with 19 haplotypes (23.7%) shared amongst at least two regional populations. None
of the haplotypes were shared among all four regional populations. Of the 80 haplotypes, 32 haplotypes (40%) occurred in low
frequencies represented by only one isolate. Moderate levels of gene diversity (H = 0.51 to 0.61) and genotypic diversity (Ĝ = 12.0 to 22.0; clonal fraction = 0.39 to 0.67) for regional populations were observed. Genotypic diversities (Ĝ) did not differ significantly among populations. All regional populations were in linkage equilibrium indicating the occurrence
of outcrossing. Low to moderate levels of population subdivision (0.03 to 0.07), were observed among regional populations.
Only one large panmictic population was inferred by Structure, indicating no significant population structure. A Mantel test showed no significant isolation by distance (r = −0.43; P = 0.18), indicating anthropogenic movement of inoculum. The results demonstrated that S. sclerotiorum populations in northern Iran, are randomly mating and have a number of shared haplotypes among regional populations; this
possibly represents recent founder populations and/or a high occurrence of anthropogenic migration of infected plant material
among populations. 相似文献
19.
Matthew P. Daugherty Joao R. S. Lopes Rodrigo P. P. Almeida 《European journal of plant pathology / European Foundation for Plant Pathology》2010,127(3):333-340
Differences in the virulence of a pathogen among host species can occur because hosts differ in their resistance or tolerance
to infection or because of underlying genetic variation in the pathogen. The xylem-limited bacterium Xylella fastidiosa is pathogenic to dozens of plant species throughout the Americas, and is structured into genetically and biologically distinct
strains. In some plants X. fastidiosa causes striking leaf scorch symptoms and in others, such as alfalfa, stunting is the primary symptom. The mechanism by which
these symptoms occur has been debated. We tested the hypothesis that symptoms result from X. fastidiosa-induced water stress, and that the magnitude of water stress is strain-dependent. We mechanically inoculated alfalfa plants
with one of 14 isolates (5 identified genetically as “almond” and 9 as “grape” isolates), and compared stable carbon isotope
ratios among isolates. Infected plants showed significant isotopic shifts (up to 2% on average) relative to healthy plants
that were consistent with water stress. Moreover, there were significant differences in water stress among isolates, with
a tendency for grape isolates to cause more severe water stress than almond isolates. There was also a positive relationship
between plant infection level and isotopic shift (slope ± SE = 0.273 ± 0.068), which supports the hypothesis that X. fastidiosa symptoms result from bacterial multiplication and vessel occlusion. Unexpectedly, however, water stress was not correlated
with measures of alfalfa stunting. These results suggest X. fastidiosa induces strain-specific levels of water stress, but factors other than water stress alone are responsible for stunting. 相似文献
20.
María I. Dinolfo Sebastian A. Stenglein María V. Moreno Paul Nicholson Philip Jennings Graciela L. Salerno 《European journal of plant pathology / European Foundation for Plant Pathology》2010,127(4):483-491
Fusarium poae is one of the Fusarium species isolated from cereal grains infected by Fusarium head blight (FHB), and in recent years it has been identified as
a major FHB component. In this study, 97 F. poae isolates from Argentina (n = 62) and England (n = 35) were analysed by inter-simple sequence repeats (ISSR) to examine the genetic diversity and to determine whether intraspecific
variation could be correlated with geographic and/or host origin. The molecular analysis showed high intraspecific variability
within F. poae isolates, but did not reveal a clear relationship between variability and the host/geographic origin. Fusarium poae isolates from the same geographic region or host appeared in different subclusters. Conversely, isolates with the same haplotype
were also collected from different geographic regions. However, we did observe subclusters consisting of isolates from Argentina
only or from England only. Furthermore, a single seed sample was found to host different haplotypes. Analysis of molecular
variance (AMOVA) indicated a high genetic variability in F. poae, with most of the genetic variability explained by differences within, rather than between Argentinean and English populations.
This is the first report on genetic diversity of F. poae using ISSR markers. Moreover, ISSR fingerprinting generates highly polymorphic markers for F. poae and proved to be a useful and reliable assay for genetic variability studies. 相似文献