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1.
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
2.
Sclerotinia sclerotiorum is an important pathogen of many crop plants which also infects wild hosts. The population structure of this fungus was studied for different crop plants and Ranunculus acris (meadow buttercup) in the UK using eight microsatellite markers and sequenced sections of the intergenic spacer (IGS) region of the rRNA gene and the elongation factor 1‐alpha (EF) gene. A total of 228 microsatellite haplotypes were identified within 384 isolates from 12 S. sclerotiorum populations sampled in England and Wales. One microsatellite haplotype was generally found at high frequency in each population and was distributed widely across different hosts, locations and years. Fourteen IGS and five EF haplotypes were found in the 12 populations, with six IGS haplotypes and one EF haplotype exclusive to buttercup. Analysis of published sequences for S. sclerotiorum populations from the USA, Canada, New Zealand and Norway showed that three of the IGS haplotypes and one EF haplotype were widely distributed, while eight IGS haplotypes were only found in the UK. Although common microsatellite and IGS/EF haplotypes were found on different hosts in the UK, there was evidence of differentiation, particularly for one isolated population on buttercup. However, overall there was no consistent differentiation of S. sclerotiorum populations from buttercup and crop hosts. Sclerotinia sclerotiorum therefore has a multiclonal population structure in the UK and the wide distribution of one microsatellite haplotype suggests spatial mixing at a national scale. The related species S. subarctica was also identified in one buttercup population. 相似文献
3.
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
4.
Genetic differentiation in populations of Exserohilum turcicum from maize and sorghum in South Africa 下载免费PDF全文
Exserohilum turcicum is the causal agent of northern leaf blight, a devastating foliar disease of maize and sorghum. Specificity of E. turcicum to either maize or sorghum has been observed previously, but molecular evidence supporting host specialization is lacking. The aim of this study was to compare the genetic structure of E. turcicum isolates collected from adjacent maize and sorghum fields in Delmas and Greytown in South Africa. In addition, the mode of reproduction of this pathogen was investigated. Isolates from maize (N = 62) and sorghum (N = 64) were screened with 12 microsatellite markers as well as a multiplex mating type PCR assay. No shared haplotypes were observed between isolates from different hosts, although shared haplotypes were detected between isolates from maize from Delmas and Greytown. Population structure and principal coordinate analyses revealed genetic differentiation between E. turcicum isolates from maize and sorghum. Analysis of molecular variance indicated higher among‐population variation when comparing populations from different hosts, than comparing populations from different locations. Lack of shared haplotypes, high proportion of private alleles, greater among‐population variance between hosts than locations and significant pairwise population differentiation indicates genetic separation between isolates from maize and sorghum. The high haplotypic diversity in combination with unequal mating type ratios and significant linkage equilibrium indicates that both sexual and asexual reproduction contributes to the population genetic structure of E. turcicum in South Africa. 相似文献
5.
Azadeh Ghaneie Rahim Mehrabi Naser Safaie Masoud Abrinbana Abbas Saidi Mostafa Aghaee 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(2):191-202
Septoria tritici blotch (STB), caused by Mycosphaerella graminicola has recently become one of the devastating diseases in Iran causing significant yield losses on most commercial bread and
durum wheat cultivars. Iran is located in the Fertile Crescent, a region where wheat was historically domesticated; and, thus,
landraces derived from this region are of considerable global interest for identification of new sources of resistance to
various stresses. Here, we report on the resistance responses of 45 tetraploid wheat landraces collected from different provinces
of Iran to eight M. graminicola isolates. In total 138 isolate-specific resistances were found among all interactions (n = 360). The highest number of specific resistances (30 out of 32 interactions) was found in wheat landraces collected from
West Azarbaijan. In contrast, all landraces from Kordestan were highly susceptible to M. graminicola isolates and only one isolate-specific resistance was identified among 106 isolate-wheat interactions. Kermanshah landraces
showed the highest resistance variation against different isolates. About 57 isolate-specific resistances were identified
among 104 interactions. Ilam landraces were highly resistant to STB as 28 specific resistances were observed among 32 interactions.
Markazi (n = 2) and Sistan-Baluchestan (n = 1) were susceptible to all isolates tested. Landraces from Lorestan were generally susceptible to isolates tested as 26
susceptible responses were observed out of 32 interactions. Our results indicate that landraces collected from the Fertile
Crescent region may possess diverse effective resistance genes or valuable broad spectrum resistance genes, and that their
identification is of interest and can be exploited in breeding programs. 相似文献
6.
Gwenaelle Comont Marie-France Corio-Costet Philippe Larignon François Delmotte 《European journal of plant pathology / European Foundation for Plant Pathology》2010,127(4):451-464
Phaeomoniella chlamydospora, (Chaetothyriales, Herpotrichiellaceae) is one of the main causal agents of Petri disease and esca on grapevines. We have
used AFLP markers to study the population genetic structure of 74 isolates collected at different spatial scales: 56 isolates
originated from vines with esca disease sampled from four French vineyards (Poitou-Charentes, Aquitaine, Languedoc-Roussillon,
Alsace); 18 isolates were collected from a single plot (Aquitaine vineyard). Significant linkage disequilibrium indicated
that P. chlamydospora populations are not panmictic, whereas the level of haplotypic diversity observed, 72 single multilocus haplotypes identified
in total among the 74 isolates analysed, suggest that reproduction in this species may not be strictly clonal. Clustering
analyses suggests the presence of two genetically differentiated but sympatric clusters of isolates. The level of differentiation
between the two clusters is high (F
ST = 0.23) and significant at 13 out of the 21 loci analyzed. The most plausible explanation for this pattern of admixture is
the coexistence in P. chlamydospora French populations of two predominant clonal lineages. Finally, the low level of spatial genetic differentiation in this
study is consistent with the spread of this fungus through the transport of infected plant material by human activities. 相似文献
7.
Ninghai Lu Jianfeng Wang Xianming Chen Gangming Zhan Changqing Chen Lili Huang Zhensheng Kang 《European journal of plant pathology / European Foundation for Plant Pathology》2011,131(4):685-693
In China, wheat stripe rust, caused by Puccinia striiformis f. sp. tritici, is one of the most destructive diseases of wheat. The Longnan and Linxia regions in Gansu Province and Qinghai Province
are the major over-summering regions for the pathogen and key epidemiological zones in Northwest China. Population genetic
diversity and interregional long-distance spread of the wheat stripe rust pathogen in Northwest China were studied using SSR
markers. The genetic diversity in the Longnan population was much higher than those in the Linxia and Qinghai populations.
Therefore, the molecular data confirmed that the Longnan region is a center of genetic diversity for P. striiformis f. sp. tritici in Northwest China. The low genetic differentiation (Gst = 0.15) and the extensive gene flow (Nm = 1.37) were found among the three regions in Northwest China. The most important conclusion of this study is that the stripe
rust inoculum in Qinghai can come from both Longnan and Linxia, but mainly from Longnan directly in the spring. 相似文献
8.
An analysis of allelic diversity at nine microsatellite loci provided an insight into the population structure of Botrytis cinerea from four fields (sampled in 2003 and 2004) that represented important regional locations for chickpea production in Bangladesh. Although three populations were limited by sample size after clone‐correction, a total of 51 alleles were amplified among 146 B. cinerea isolates from Bangladesh, which revealed a high amount of within‐population and overall genetic diversity (HS = 0·48 and HT = 0·54, respectively). The percentage of maximal genotypic diversity (G) ranged between populations (G = 23–40), with a total of 69 haplotypes detected (G = 25). Bayesian cluster analysis depicted two major clusters distributed among the four Bangladesh populations, indicating population admixture from two origins that have spread throughout these regions. Genotype flow between regions was detected and indicated the spread of clonal lineages, consistent with relatively low differentiation among the four populations (mean GST = 0·1, P < 0·05). These results highlighted the potential threat of host resistance breakdown as a result of considerable genetic diversity, genotype flow and the evolutionary potential of B. cinerea. 相似文献
9.
Norio KONDO Yuki KOBAYASHI Futoshi SAKUMA Shohei FUJITA Kippei MURATA 《Journal of General Plant Pathology》2002,68(4):284-291
The distribution of two races (1 and 2) of Phialophora gregata f. sp. adzukicola, the causal agent of brown stem rot of adzuki bean, was examined using a total of 483 isolates obtained from 39 fields in
19 locations on Hokkaido, Japan between 1997 and 1999. Race 1 was predominant (416 isolates or 86.1%) in the commercial fields
tested. Race 2 was found in 25 fields (64.1%), including two fields of cultivar Kita-no-otome (resistant to race 1, but susceptible
to race 2), indicating that race 2 was widely distributed in most of the production areas in Hokkaido. Using amplified fragment
length polymorphisms (AFLP), a total of 67 polymorphic AFLP markers was recorded among 72 representative isolates (37 and
35 isolates of races 1 and 2, respectively), and 57 distinct haplotypes were detected. Cluster analysis revealed no close
correlation between races and AFLP groups. Thus, no difference was observed between values of gene diversity in each race
(0.253 and 0.284 in races 1 and 2, respectively), and the coefficient of gene differentiation was very low (G
ST
=0.015). Gene differentiation between both races by analysis of molecular variance was not significantly different from zero
(Φ=−0.001; p=0.403). However, the results of gene differentiation among regional populations (G
ST
=0.290, Φ=0.292; p<0.001) are not necessarily consistent with the result that isolates from the same district were generally not tightly clustered.
Received 15 April 2002/ Accepted in revised form 6 September 2002 相似文献
10.
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
11.
Jinxiu Zhang Allen G. Xue Malcolm J. Morrison Yao Meng 《European journal of plant pathology / European Foundation for Plant Pathology》2011,131(1):95-102
This study evaluated the impact of time between the application of cell suspensions or cell-free filtrates of Bacillus subtilis strains SB01 or SB24 on soybean plants under field conditions and inoculation with Sclerotinia sclerotiorum on their effectiveness for suppression of S. sclerotiorum. The results showed that the cell suspensions of two strains provided greater effectiveness than the cell-free filtrates,
but the suppression effectiveness decreased as the time between application in the field and S. sclerotiorum inoculation increased. The B. subtilis cell suspensions applied on soybean leaves for up to 10 days under field conditions were able to provide a significant (P < 0.01) reduction in disease severity by approximately 20–90% at 5 days after the S. sclerotiorum inoculation. When rated 15 days after S. sclerotiorum inoculation, plants treated with bacterial cells for ≤6 days reduced Sclerotinia stem rot severity by 15–70%. Most effectiveness was provided by the cell suspensions present on soybean leaves for <3 days
under field conditions, which significantly (P < 0.01) reduced disease severity by 40–70% over 15 days. In comparison, the cell-free filtrates remaining on leaves for <6 days
significantly (P < 0.01) reduced disease severity during the first 5 days after the inoculation, while the best cell-free filtrate treatments
were those with ≤1-day intervals, which significantly (P < 0.01) reduced disease severity by 10–40% during 15 days after the inoculation. The effectiveness of B. subtilis was reduced when it rained after application. 相似文献
12.
Molecular,morphological and pathogenic diversity of Sclerotinia sclerotiorum isolates from common bean (Phaseolus vulgaris) fields in Argentina 下载免费PDF全文
C. L. Abán G. Taboada Y. Spedaletti M. Aparicio R. N. Curti N. B. Casalderrey M. E. Maggio M. O. Chocobar M. Salgado M. Z. Galván 《Plant pathology》2018,67(8):1740-1748
White mould, caused by Sclerotinia sclerotiorum, is one of the most threatening fungal diseases occurring across major bean production regions worldwide. In Argentina, under favourable weather conditions, up to 100% seed yield losses occur on susceptible common bean cultivars. The aim of this study was to characterize the diversity of S. sclerotiorum isolates from six dry bean fields in the main production area of Argentina by means of molecular, morphological (mycelium colour, number and pattern of sclerotia distribution) and pathogenic approaches. Among 116 isolates analysed, high genotypic and morphological variability was observed. A total of 52 mycelial compatibility groups (MCGs) and 59 URPs (universal rice primers) molecular haplotypes were found. All the MCGs were location specific, while only 12% of the URP haplotypes were shared among locations. The molecular analysis of variance revealed a significant differentiation among populations, with higher genetic variability within the populations analysed than among them. The aggressiveness of the isolates towards bean seedlings was assessed in the greenhouse. Most of the isolates were highly aggressive, while no variation among locations was observed. The information generated in the present study provides, for the first time, information on the variability of S. sclerotiorum associated with white mould in the main common bean production area in Argentina. In addition, the findings suggest the occurrence of both clonal and sexual reproduction in the populations analysed. This work contributes to the development of sustainable management strategies in bean production aimed to minimize yield losses due to white mould. 相似文献
13.
Genetic structuring and diversity patterns along rivers – local invasion history of Ambrosia artemisiifolia (Asteraceae) along the Danube River in Vienna (Austria) shows non‐linear pattern 下载免费PDF全文
Ambrosia artemisiifolia is an annual weed from North America that nowadays is invasive in many countries worldwide. In Austria, numerous populations of A. artemisiifolia are located along the Danube River, especially along the ‘New Danube’ (Vienna). This area is characterised by ruderal and riparian sites, which are regularly flooded. To better understand the spread of A. artemisiifolia and its colonising behaviour along the Danube River, we analysed genetic structure and diversity based on 23 populations linearly arranged along the Viennese Danube riverbed and upstream, utilising the Amplified Fragment Length Polymorphism (AFLP) fingerprint method. We generated 284 polymorphic AFLP markers across 446 A. artemisiifolia plants. The genetic diversity within populations was higher (HW = 0.091) than among populations (HB = 0.007). This result indicates A. artemisiifolia introductions from similar mixtures of sources or spread from a single already mixed introduction. Within our local setting, we were unable to identify neither source or sink populations nor an obvious linear genetic structuring. Genetic among‐population differentiation was low to moderate (amova ‐derived FST = 0.124). Lack of geographical structuring is indicative of highly dynamic gene flow, which is further supported by the absence of an isolation‐by‐distance pattern. Multiple introductions and non‐directional gene flow are most likely promoted by anthropogenic disturbance and human‐mediated dispersal. Our results demonstrate the ability and speed of A. artemisiifolia to settle in newly disturbed areas and the difficulties to predict invasion directions, as downstream river dispersal was negligible. 相似文献
14.
Ziqin Li Yingchun Wang Yu Chen Jinxiu Zhang W. G. Dilantha Fernando 《Phytoparasitica》2009,37(1):77-85
Ninety-six isolates of sunflower Sclerotinia sclerotiorum (Lib.) de Bary from Inner Mongolia (IM) in China, from Canada and the United Kingdom (UK) were sampled to investigate the
genetic diversity and structure using Sequence-Related Amplified Polymorphism. A total of 123 polymorphic bands were obtained,
ranging in size from 100 to 500 base pairs. The five populations of S. sclerotiorum isolated from the three countries showed various levels of genetic variability. The percentage of polymorphic loci varied
from 30.89% in the UK population to 97.56% in the Middle IM population. The values of Shannon index (i) varied from 0.1876 in the UK population to 0.5301 in the West IM population. The heterozygosity of the five geographic populations
obtained by estimating allele frequency varied from 12.91% in the UK population to 35.44% in the West IM population. The genetic
identity, as indicated by the Nei unbiased identity index, ranged from 0.9744 between populations from Canada and East IM
to 0.6477 between populations from West IM and UK. UPGMA cluster analysis using Nei’s genetic distance gave distances ranging
from 0.0259 to 0.4343. The rates of gene flow among five geographic populations ranged from 1.5406 between West IM and UK
populations to 18.4149 between West IM and Middle IM populations. The four populations from West IM, Middle IM, East IM and
Canada were clustered into one subgroup in which the isolates from West and Middle IM belonged to one population, whereas
those from East IM and Canada essentially were another population. The isolates from the UK formed a population that was significantly
distinct from other populations. 相似文献
15.
María M. Reynoso Sofía N. Chulze Kurt A. Zeller Adriana M. Torres John F. Leslie 《European journal of plant pathology / European Foundation for Plant Pathology》2009,123(2):207-215
Fusarium verticillioides (sexual stage Gibberella moniliformis) is a common fungal pathogen of maize worldwide that also produces fumonisin mycotoxins. Populations of this fungus can be
diverse with respect to neutral and selectable genetic markers. We used vegetative compatibility groups (VCGs) and amplified
fragment length polymorphisms (AFLPs) to evaluate the genetic structure of three F. verticillioides populations from commercial maize fields in Argentina. Based on work with similar populations from outside South America,
we expected individuals within the populations to be genetically diverse, that genotypic variation would be distributed in
a manner consistent with random mating, and that populations from different locations would be genetically indistinguishable
from one another. We analysed 62 AFLP loci for 133 fungal isolates. All three populations were genotypically diverse but genetically
similar and potentially part of a larger, randomly mating population, with significant genetic exchange occurring between
the three subpopulations. There was no evidence for linkage disequilibrium at P = 0.05. The low values of G
ST
, the lack of frequent private alleles, and the lack of a systemic pattern of linkage disequilibrium all suggest that sexual
reproduction is sufficiently common in F. verticillioides and that the dispersal of strains is sufficiently efficient for the population of F. verticillioides in the main maize growing region to be a single randomly mating population with no detectable genetic subdivision. Thus differences
in disease and/or toxin production observed in this region are best attributed to differences other than the genetic composition
of the population. 相似文献
16.
Jalal Soltani Ali A. Aliabadi 《European journal of plant pathology / European Foundation for Plant Pathology》2010,128(1):65-70
Bacterial blight disease of Persian walnut (Juglans regia, L.), caused by Xanthomonas arboricola pv. juglandis (Xaj), leads to significant nut losses in northern, central and western areas of Iran. To identify the natural sources of resistance
to disease in the endemic walnut genotypes of Iran, sixteen walnut genotypes, collected from different areas of Hamedan province,
were inoculated with Xaj in a randomized complete block design with five replicates for each genotype. Two-year old genotypes were gently sprayed
with a suspension of bacteria adjusted to approximately 2 × 109 cfu ml−1 of distilled water in May. Infected leaves were rated for disease 28 and 42 days after inoculation, using a 0 to 5 severity
scale, based on the number, size and distribution of lesions on the leaves. Data analyses showed that there were variations
among genotypes in response to pathogen. Upon inoculation by bacterial suspension genotype 94 showed the highest resistance
to both disease incidence and its progress after 4–6 weeks of infection. Genotype 65 showed high susceptibility to disease
and genotype 69 showed high susceptibilities both to disease incidence and its progress after 4–6 weeks of infection. 相似文献
17.
Firas Talas Heiko K. Parzies Thomas Miedaner 《European journal of plant pathology / European Foundation for Plant Pathology》2011,131(1):39-48
Fusarium head blight (FHB) is one of the most destructive diseases of wheat. Twelve small commercial wheat fields (size 1–3
hectares) were sampled in Germany for Fusarium populations at three spots per field with 10 heads each. PCR assays using generic primers confirmed 338 isolates as F.graminearum sensu stricto (s.s.) (64.9%) out of 521 Fusarium spp. that were further analyzed. Populations of F. graminearum s.s. in Germany contain three types of trichothecenes with a dominancy of 15-acetyldeoxynivalenol chemotype (92%) followed
by 3-acetyldeoxynivalenol chemotype (6.8%) and a few isolates of nivalenol chemotype (1.2%). All these isolates were genotyped
using 19 microsatellite loci. The 12 populations showed a high genetic diversity within the small scale sampling areas resulting
in 300 different haplotypes. Genetic diversity within populations (71.2%) was considerably higher than among populations (28.8%)
as shown by analysis of molecular variance. Gene flow (Nm) between populations ranged from 0.76–3.16. Composition of haplotypes
of one population followed over 2 years changed considerably. No correlation between genetic and geographical distance was
found. In conclusion, populations of F. graminearum s.s. in Germany display a tremendous genetic variation on a local scale with a restricted diversity among populations. 相似文献
18.
Yosuke Matsushita Tomio Usugi Shinya Tsuda 《European journal of plant pathology / European Foundation for Plant Pathology》2010,128(2):165-170
We isolated eight polymorphic microsatellite markers for the basidiomycete Armillaria cepistipes and characterised them by analysing 50 isolates representing two geographically distinct populations from Switzerland and
the Ukraine. The number of alleles per locus and population varied from one to eight, resulting in 43 alleles over the eight
loci and two populations. In both populations, no significant linkage disequilibrium was observed between pairs of loci. Significant
(P < 0.05) deviations from Hardy-Weinberg equilibrium were observed at one locus in the Swiss population and at three loci in
the Ukrainian population. Of the eight loci developed for A. cepistipes, six were also polymorphic in A. gallica, four in A. ostoyae, two in A. mellea, and one in A. borealis. Beside the potential to be used for population genetic studies on A. cepistipes, these microsatellites thus represent additional molecular markers for three of the four annulated Armillaria species occurring in Europe. 相似文献
19.
Rhizoctonia solani anastomosis group 4 (AG‐4) is a serious pathogen causing damping off and root rot in many important crop plants. A total of 190 isolates of R. solani AG‐4 HG‐I were collected from host fields in five provinces of Iran. The genetic structure of this pathogen was evaluated using seven microsatellite loci, focusing particularly on geographic differentiation. Most of the multilocus genotypes (MLGTs) were unique, with few MLGTs shared among populations. High to moderate levels of gene flow among populations was indicated by low to moderate differentiation between pairs of populations based on the fixation index (FST). Gametic equilibrium of most pairs of microsatellite loci and moderate genotypic diversity were found for two out of five populations, indicating that these populations were sexually recombining in structure. High genotypic diversity, moderate clonal fractions and site‐specific genotypes were consistent with mixed reproductive systems for the remaining populations. The findings of departures from Hardy–Weinberg (HW) equilibrium, gametic disequilibrium and a significant excess of homozygotes in half or more than half of the loci were probably caused by the presence of null alleles and the Wahlund effect. This is the first study to consider the population genetics of the root and crown rot pathogen R. solani AG‐4. 相似文献
20.
Pathotypic and genetic diversity in the population of Rhizoctonia solani AG1‐IA causing rice sheath blight in China 下载免费PDF全文
Sheath blight, caused by Rhizoctonia solani AG1‐IA, is one of the most serious diseases of rice. In this study, a total of 175 isolates of R. solani AG1‐IA were collected from five rice‐growing regions in China. Pathogenicity tests revealed that all isolates were virulent to five cultivars with different levels of resistance at the rice seedling stage in the greenhouse. There was considerable variation in aggressiveness, and the isolates were classified into three pathotypes based on disease severity, with moderately virulent isolates prevalent in the population. Forty‐three haplotypes were identified based on ITS sequencing, and 39 haplotypes were distinct among isolates. There were high levels of haplotype diversity and nucleotide diversity within the populations of R. solani AG1‐IA. High gene flow (Nm = 1·63–5·22) was detected, consistent with relatively low differentiation between pairs of populations. Five populations were divided into two distinct clusters by the unweighted pair group method with arithmetic mean (UPGMA), and no spatial population differentiation was discernible. The majority (97·8%) of genetic diversity was distributed among isolates within populations, with only 2·2% of the genetic diversity attributed to differences among populations. The star‐like shape of the haplotype network provided evidence of signatures of population expansion in recent history. No significant relationships were found between the genetic diversity and aggressiveness or geographic origin among populations of R. solani AG1‐IA. These results highlight that the population characteristics of R. solani AG1‐IA should be taken into account in evaluating the germplasm resistance of rice cultivars to sheath blight. 相似文献