首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Cryphonectria parasitica, the causal agent of chestnut blight, has been present in Slovenia since at least 1950. To improve understanding of its diversity, 254 isolates of the fungus from 11 Slovenian populations were sampled. Fifteen vegetative compatibility (vc) types were identified. The dominant vc type was EU‐13, comprising 40·1% of all isolates tested, followed by EU‐1 (19·7%), EU‐2 (12·2%) and EU‐12 (9%). The vc type diversity in the most diverse population sampled in Slovenia was higher than in the populations found previously in northern Italy and Croatia. Both mating types and perithecia were observed in surveyed populations. Natural hypovirulence was found in six out of seven populations tested, with frequencies ranging from 72·2% in the population sampled near the Croatian border to 11·1% in the population sampled near the Austrian border. All identified hypoviral isolates (21) belonged to the Italian subtype of Cryphonectria hypovirus 1 and were closely related to the hypoviruses found in other European countries. Despite the high vc type diversity, incidence of hypovirulence was also high, indicating widespread natural biological control of the disease.  相似文献   

2.
In order to improve understanding of its diversity, 338 isolates of Cryphonectria parasitica, the causal agent of chestnut blight, were sampled from 10 chestnut populations throughout chestnut‐growing coastal and continental areas of Croatia. Eighteen vegetative compatibility (VC) types were identified. The VC type EU‐1 was the most widespread, comprising 42·9% of the isolates, followed by EU‐2 (21%) and EU‐12 (14·2%). In respect to the occurrence of the main VC types, the C. parasitica populations in Croatia combined features of both northwestern and southeastern European populations. Perithecia and mating‐type ratios of approximately 1 : 1 were found in all populations, suggesting that sexual reproduction of the fungus is common in Croatia. Natural hypovirulence was also evident in all populations, with incidence of hypovirus‐infected isolates ranging from 12·7% in Istria‐Buje to 66·6% in the continental part of the country. A total of 36 hypovirus‐infected isolates sampled throughout Croatia were analysed in ORF‐A and ORF‐B by RT‐PCR/RFLP analysis. All viral isolates belonged to the Italian subtype of Cryphonectria hypovirus 1 (CHV‐1) and were closely related to the isolates found in other European countries. The RFLP patterns found were also identical or similar to the patterns of three isolates collected in Croatia 22 years ago, suggesting a slow evolution of the hypovirus.  相似文献   

3.
  相似文献   

4.
The objective of this study was to determine whether genetically differentiated groups of Puccinia triticina are present in Europe. In total, 133 isolates of P. triticina collected from western Europe, central Europe and Turkey were tested for virulence on 20 lines of wheat with single leaf rust resistance genes, and for molecular genotypes with 23 simple sequence repeat (SSR) markers. After removal of isolates with identical virulence and SSR genotype within countries, 121 isolates were retained for further analysis. Isolates were grouped based on SSR genotypes using a Bayesian approach and a genetic distance method. Both methods optimally placed the isolates into eight European (EU) groups of P. triticina SSR genotypes. Seven of the groups had virulence characteristics of isolates collected from common hexaploid wheat, and one of the groups had virulence characteristics of isolates from tetraploid durum wheat. There was a significant correlation between the SSR genotypes and virulence phenotypes of the isolates. All EU groups had observed values of heterozygosity greater than expected and significant fixation values, which indicated the clonal reproduction of urediniospores in the overall population. Linkage disequilibria for SSR genotypes were high across the entire population and within countries. The overall values of RST and FST were lower when isolates were grouped by country, which indicated the migration of isolates within Europe. The European population of P. triticina had higher levels of genetic differentiation compared to other continental populations.  相似文献   

5.
In recent years, Pinus plantation forestry has been significantly hampered by outbreaks of pitch canker caused by the fungus Fusarium circinatum. This study investigated the role of Pinus host, geographic origin and reproductive mode in structuring the F. circinatum populations in plantations. For this purpose, 159 isolates originating from diseased plantation trees in the Western and Eastern Cape Provinces of South Africa were genotyped using 10 microsatellite markers. Analyses of these data revealed 30 multilocus haplotypes and that the populations were distinct based on geographic origin as well as host. However, shared haplotypes were observed between populations, showing that these populations are connected, possibly through the movement of haplotypes. A second aim was to determine whether the genetic variation found in these populations of the fungus could be attributed to outbreaks of the seedling disease caused by this pathogen in Pinus nurseries. To achieve this goal, an additional set of 43 isolates originating from pine seedling nurseries was genotyped and analysed. The results showed that the populations of F. circinatum in plantations most probably originated from the nursery outbreaks that occurred prior to the plantation outbreak. Inferences regarding reproductive mode further showed that sexual reproduction has little impact on the genetic makeup of the F. circinatum populations and that they primarily reproduce asexually. Overall, the results of this study showed that the F. circinatum diversity in South Africa has arisen due to multiple introductions of the pathogen and is not due to sexual reproduction.  相似文献   

6.
Since 1911, dothistroma needle blight, caused by Dothistroma septosporum, has been recorded in most European countries. In the Czech Republic, the fungus has become an important disease of pines since 2000, especially Austrian pines in plantations of Christmas and ornamental trees. The aim of this study was to analyse the population structure, gene flow and mode of reproduction of this pathogen. Microsatellite and mating‐type markers were analysed in a Dothistroma population in the southeastern part of the country using reference isolates from other European countries. The haplotypic diversity was high, with 87 unique and 13 shared haplotypes (probable clones) identified in 121 samples. Based on structure analysis, the isolates were divided into two populations, with an uneven distribution over the sampling sites. The grouping of the sites to the populations did not follow a geographical pattern because certain isolates that were sympatrically co‐occurring at the same site were placed in different populations. Tests for random mating (the index of association and a parsimony tree‐length permutation test) showed a significant clonal mode of reproduction in most cases, but the intrapopulation haplotypic diversity is unexpectedly high. Although a teleomorphic stage of D. septosporum has not been previously observed in the Czech Republic, the high intrapopulation haplotypic diversity can be explained by infrequent sexual reproduction consistent with the occurrence of both mating types.  相似文献   

7.
Erwinia amylovora is the causative agent of fire blight, a destructive disease of rosaceous plants. The European population can be divided into several subtypes according to differences in restriction fragment length polymorphism of the XbaI genomic DNA digest analysed with pulsed-field gel electrophoresis. This technique was also used to determine the genetic relatedness of six Croatian isolates to the E. amylovora types found in the countries surrounding Croatia. The isolates belong to the Pt2 pattern type that is characteristic of the East Mediterranean basin. All tested isolates gave essentially the same total cell protein pattern in SDS-polyacrylamide gel electrophoresis. The number of short-sequence DNA repeats in plasmid pEA29 of six isolates was determined by PCR assays and ranged from four to seven. The isolates examined showed high pathogenicity in immature pear fruits. Differences were also revealed in microbiological assays such as amylovoran synthesis, levan formation, siderophore production and colour on coliform medium.  相似文献   

8.
During 2012, an official survey was conducted for Monilinia species present on peach and nectarine in Croatia. In total, 169 Monilinia spp. isolates were collected from 24 commercial orchards and identified according to morphology in culture and PCR. Eighty of the isolates were identified as Monilinia laxa, 70 as M. fructigena and 19 as M. fructicola. M. fructicola was found only at one location in the Mediterranean part of the country, and this is the first record of this quarantine fungus in Croatia. PCR diagnostic tests using M. fructicola‐specific primer pair MO368‐5/MO368‐10R repeatedly gave false negatives for some isolates. PCR tests using primer pair ITS1‐Mfc1/ITS4‐Mfc1 amplified M. fructicola‐specific product in all isolates and was therefore shown to be more suitable for diagnostic purposes.  相似文献   

9.
Chestnut blight, caused by Cryphonectria parasitica, was identified in Devon, UK, in December 2016. Intensive surveys detected the disease at further sites in Devon (seven), Berkshire (one), Dorset (one), Derbyshire (four) and a cluster of eight sites in southeast London. Over 570 survey samples were tested, and 227 were positive for C. parasitica by isolation and real-time PCR. A total of 227 isolates were tested for mating type, and 197 screened for vegetative compatibility group (VCG) and compared with VCGs known from mainland Europe. The same isolates were also screened for the presence of Cryphonectria hypovirus 1 (CHV-1). Eleven VCGs were identified within the UK population. Five corresponded to already known European VCGs but six were unique. The European VCGs mainly came from the Devon, Dorset, Berkshire and Derbyshire disease outbreaks, whilst unique VCGs were almost exclusively from the southeast London cluster. Both mating types were detected, but only one mating type was present at each site, with the exception of a single Devon site. Perithecia of C. parasitica were never observed at any site. CHV-1 was found in seven isolates from three different locations and was always subtype-I, which has limited hypovirulence. Therefore, although CHV-1 is associated with C. parasitica at some outbreaks, it probably has limited impact on virulence. The diversity of VCGs and their distribution at outbreak sites, together with findings of CHV-1, suggests C. parasitica has been introduced to the UK multiple times over at least two decades through international plant trade.  相似文献   

10.
Phytophthora pluvialis is the causal agent of red needle cast on Pinus radiata in New Zealand. It was first isolated in 2008 but had previously been recovered from tanoak (Notholithocarpus densiflorus) and Douglas‐fir (Pseudotsuga menziesii) trees in Oregon, USA in 2002. Phytophthora pluvialis was subsequently described as a new species in 2013 and classified as a clade III Phytophthora species. The aim of this study was to gain a better understanding of the genetic diversity, population structure and origin of this pathogen. A total of 360 P. pluvialis isolates were collected from the USA and New Zealand. The genome sequences of two P. pluvialis isolates were used to identify 27 single nucleotide polymorphism (SNP) markers that were then used to genotype the two populations. The genotypic data showed that the USA population of P. pluvialis had twice the genetic diversity and a greater number of multilocus genotypes (MLGs) compared to the New Zealand population, with 126 and 24 MLGs, respectively. The majority of the subpopulations within the USA and New Zealand showed linkage disequilibrium. All subpopulations had a negative fixation index, indicating that clonal reproduction is prevalent in both countries. A minimum spanning network (MSN) showed two unique clusters of isolates in the New Zealand population, suggesting two potential introductions of P. pluvialis into New Zealand from the USA. There was no significant structure within the New Zealand or USA populations. This study provides novel insight into the genetic structure of P. pluvialis in New Zealand and the USA.  相似文献   

11.
In order to characterize the pathogen(s) responsible for the outbreak of fusarium diseases in Algeria, 48 Fusarium spp. isolates were collected from diseased tomato in Algeria and compared with 58 isolates of Fusarium oxysporum originating from seven other Mediterranean countries and 24 reference strains. Partial sequences of the translation elongation factor EF‐1α gene enabled identification of 27 isolates as F. oxysporum, 18 as F. commune and three as F. redolens among the Algerian isolates. Pathogenicity tests confirmed that all isolates were pathogenic on tomato, with disease incidence greater at 28°C than at 24°C. All isolates were characterized using intergenic spacer (IGS) DNA typing, vegetative compatibility group (VCG) and PCR detection of the SIX1 (secreted in xylem 1) gene specific to F. oxysporum f. sp. lycopersici (FOL). No DNA polymorphisms were detected in the isolates of F. redolens or F. commune. In contrast, the 27 Algerian isolates of F. oxysporum were shown to comprise nine IGS types and 13 VCGs, including several potentially new VCGs. As none of the isolates was scored as SIX1+, the 27 isolates could be assigned to F. oxysporum f. sp. radicis‐lycopersici (FORL). Isolates from Tunisia were also highly diverse but genetically distinct from the Algerian isolates. Several Tunisian isolates were identified as FOL by a PCR that detected the presence of SIX1. The results show that isolates from European countries were less diverse than those from Tunisia. Given the difference between Algerian populations and populations in other Mediterranean countries, newly emergent pathogenic forms could have evolved from local non‐pathogenic populations in Algeria.  相似文献   

12.
Signs and symptoms of a disease similar to those of armillaria root rot have recently been observed on various native woody plants on the foothills of Table Mountain in South Africa, one of the most botanically diverse natural environments globally. This is of concern because the root rot fungus Armillaria mellea has previously been shown to be an alien pathogen of European origin in planted gardens in the City of Cape Town. An aim of this study was to identify the cause of the root rot disease on infected plants. Based on DNA‐sequence phylogeny, it was shown that isolates collected from at least 16 native tree and woody shrub species represented the non‐native A. mellea. Microsatellite markers were then used to determine the genetic diversity and population structure of the A. mellea isolates from Table Mountain and two planted gardens where the pathogen has previously been found. Population genetic analyses revealed low levels of gene diversity and no population differentiation amongst the three populations. The results provide the first firm evidence that A. mellea has escaped the planted environment and invaded a sensitive and ecologically important natural woody environment in South Africa. This is only the second definitive case of a non‐native tree pathogen invading a natural ecosystem in the country.  相似文献   

13.
The pinewood nematode, Bursaphelenchus xylophilus, native to North America (NA), is now a major invasive pine pest in Eurasia. Pine species differ greatly in their susceptibility to B. xylophilus, and differences in susceptibility might be related to differences in phytochemistry. This study addressed two major questions: (i) which plant chemical profiles (including compounds that act as plant defences and those important for nutrition) favour pinewood nematode development; and (ii) are NA and Portuguese pinewood nematodes different in their capacity to subsist on plant tissues? For this, B. xylophilus isolates from NA and Portugal were tested on pine phloem and xylem of different pine species. It was found that unaltered pine phloem can sustain the population growth of B. xylophilus, but only in a few cases, and this was clearly related to distinct chemical profiles in some pine species. No evidence was found of evolutionary divergence between B. xylophilus populations in Portugal and NA. The pine species with phloem on which pinewood nematodes could grow tended to have low levels of total phenols, condensed tannins, flavonoids and lignin. Evidence was also found that nutrients such as N may be important.  相似文献   

14.
Light leaf spot, caused by the ascomycete Pyrenopeziza brassicae, is an established disease of Brassicaceae in the United Kingdom (UK), continental Europe, and Oceania (OC, including New Zealand and Australia). The disease was reported in North America (NA) for the first time in 2014 on Brassica spp. in the Willamette Valley of western Oregon, followed by detection in Brassica juncea cover crops and on Brassica rapa weeds in northwestern Washington in 2016. Preliminary DNA sequence data and field observations suggest that isolates of the pathogen present in NA might be distinct from those in the UK, continental Europe, and OC. Comparisons of isolates from these regions using genetic (multilocus sequence analysis, MAT gene sequences, and rep-PCR DNA fingerprinting), pathogenic (B. rapa inoculation studies), biological (sexual compatibility), and morphological (colony and conidial morphology) analyses demonstrated two genetically distinct evolutionary lineages. Lineage 1 comprised isolates from the UK, continental Europe, and OC, and included the P. brassicae type specimen. Lineage 2 contained the NA isolates associated with recent disease outbreaks in the Pacific Northwest region of the USA. Symptoms caused by isolates of the two lineages on B. rapa and B. juncea differed, and therefore “chlorotic leaf spot” is proposed for the disease caused by Lineage 2 isolates of P. brassicae. Isolates of the two lineages differed in genetic diversity as well as sensitivity to the fungicides carbendazim and prothioconazole.  相似文献   

15.
Dothistroma pini is one of two pathogens causing Dothistroma needle blight (DNB), a foliar disease of pines. The species was redefined in 2004 and subsequently recorded in several European countries. In Slovakia, the first report of the pathogen was in 2013. In this study, the population structure, genetic diversity, and reproductive mode of 105 isolates collected from 10 localities and seven hosts were determined in Slovakia. Species-specific mating type markers, ITS haplotype determination, and 16 microsatellite markers were used to characterize and genotype the isolates. Overall, 15 unique multilocus haplotypes (MLHs) based on microsatellite markers and three ITS haplotypes were identified. Three independent methods (DAPC, STRUCTURE, EDENetwork) separated the isolates into two distinct population clusters corresponding with ITS haplotypes. A high level of clonality was recorded suggesting that conidia are the primary source of pathogen dispersal. The low genetic diversity, predominantly asexual reproductive mode of the pathogen, and the fact that most isolates were collected from introduced tree species and native species in artificially planted urban greenery, supports the hypothesis that D. pini has been recently introduced into Slovakia.  相似文献   

16.
Leaf rust, caused by the fungus Puccinia triticina, is one of the most damaging rust diseases of wheat in Russia. Populations of P. triticina were monitored in seven regions of Russia from 2001 to 2018, with a total of 5,191 single urediniospore isolates from bread wheat (Triticum aestivum) being analysed. Populations have changed significantly in all regions since 2012, after 2 years of drought (2010–2011). Regional collections of P. triticina were also significantly different between the two periods 2001–2009 and 2012–2018, with changes along two geographic gradients from West Siberia to the north-west and south-west (North Caucasia) of the European part of Russia. All tested isolates were avirulent to resistance gene Lr9 in 2001–2009 but, since 2010, virulence to Lr9 has occurred and annually increased in the Asian part of Russia (Ural and West Siberia) due to deployment of cultivars with the Lr9 gene. Virulence to Lr2a and Lr15 was considerably lower in Dagestan (6%–33%) and all European regions (35%–67%) than in Asian regions (84%–96%). During 2001–2009, virulence on Lr1 was also lower in Dagestan (33%) and the European regions (50%–77%) than in Asia (91%–96%); however, by 2012–2018, nearly all isolates were virulent on Lr1. Remarkable changes were observed in frequencies of P. triticina races defined by their virulence/avirulence to Lr1 and Lr2a genes. We postulate the P. triticina population in Dagestan is specific to that area and pathogen populations in European and Asian parts of Russia are distinct.  相似文献   

17.
Colletotrichum isolates (457) were collected from strawberry plant tissues with and without typical anthracnose symptoms and from symptomless weeds in 19 Belgian strawberry fields. The isolates were characterized based on genetic, morphological and pathological features. Isolates were classified according to rDNA‐ITS sequencing: 97% of 211 representative isolates were C. acutatum, 2%C. gloeosporioides and 1%C. coccodes. The C. acutatum isolates belonged to the intraspecific groups A2 (33%), A3 (5%), A4 (50%), A5 (3%) and A7 (6%). Differences in spore morphology, growth rate and colony colour of a selection of 146 isolates confirmed the genetic grouping. Multiple Colletotrichum genotypes were detected in the same field. There was no association between the most common genotypes and geographic origin, presence or absence of symptoms, nor plant species or plant part. Representative Belgian Colletotrichum isolates were used in pathogenicity tests, together with European and American reference isolates. The C. acutatum A2 and the Belgian C. gloeosporioides isolates were the most aggressive on fruits, followed by C. acutatum A3, A4, A5, A7 and C. coccodes isolates. When inoculated into crowns, C. acutatum A2, A5 and American C. gloeosporioides isolates were the most aggressive, followed by C. acutatum A3 isolates. The A4 and A7 isolates and all European C. gloeosporioides isolates were non‐pathogenic on crowns. These data indicate that an unusually diverse Colletotrichum population is present in Belgium. The traditional differentiation between C. acutatum and C. gloeosporioides as causal agents of fruit and crown rot, respectively, proved not to be valid in Belgian strawberry fields.  相似文献   

18.
Phytophthora ramorum has been detected in official plant health surveys on Rhododendron, Viburnum and Camellia in ornamental nurseries in northern Spain since 2003. A collection of 94 isolates of P. ramorum was obtained from 2003 to 2008 from plants with symptoms at different geographical locations. Isolates were identified based on morphology and sequence of the rDNA ITS region. Mating type, genetic variation, sensitivity to phenylamide fungicides and aggressiveness of these isolates were determined. All isolates belonged to the A1 mating type, ruling out the possibility of genetic recombination. Seven microsatellite markers were used to study genetic diversity; three out of the seven microsatellite markers were polymorphic within the Spanish population of P. ramorum. This study confirms that all Spanish isolates of P. ramorum belonged to the EU1 lineage. Twelve intralineage genotypes were detected, five that are unique to Spain (EU1MG38, EU1MG41, EU1MG37, EU1MG39 and EU1MG40) and seven that are also present in at least one other European country (EU1MG1, EU1MG29, EU1MG22, EU1MG13, EU1MG2, EU1MG18 and EU1MG26). Genotypes EU1MG37, EU1MG39 and EU1MG40 were isolated from Rhododendron from one region; EU1MG38 and EU1MG41 were isolated from Camellia from two different regions. Isolates of genotype EU1MG38 were resistant to metalaxyl and mefenoxam. The level of genetic diversity within the Spanish population of P. ramorum is limited and indicates a relatively recent clonal expansion.  相似文献   

19.
Lasiodiplodia theobromae is one of the most frequent fungal pathogens associated with dieback, gummosis, leaf spot, stem-end rot and fruit rot symptoms in cashew, mango, papaya and grapevine. In this study, the variation in the genetic diversity of 117 L. theobromae isolates from northeastern Brazil (n = 100) and Mexico (n = 17), which were collected from these four crops, was analysed using microsatellite markers. The results revealed low genetic diversity among L. theobromae populations and the existence of two genetic groups. All Mexican isolates were grouped with Brazilian isolates, suggesting a low level of differentiation between these populations. Furthermore, no evident host or climate-based population differentiation was observed for L. theobromae in Brazil. The populations studied were mostly clonal, but additional studies are needed to better understand the mode of reproduction of the pathogen. The low genetic diversity of L. theobromae populations in northeastern Brazil suggests that resistant cultivars could be used as a durable management strategy to reduce the impact of the diseases caused by this pathogen.  相似文献   

20.
The almost simultaneous outbreaks of Pepino mosaic virus in tomato crops in different European and non-European countries, was reason to have a closer look at the relationship between these isolates and the original isolate from pepino. Fifteen isolates from tomato from different locations and the original pepino isolate, were compared on the basis of their symptomatology on a series of plant species. In addition, PCR fragments derived from the viral polymerase gene were sequenced and aligned. Both studies showed that the isolates from tomato clearly differed from the pepino isolate. The different tomato isolates, however, exhibited only minor differences to each other, both in symptomatology and nucleotide sequence. These results support the conclusion that the tomato isolates should be considered as a distinct strain (Mumford and Metcalfe (2001) Archives of Virology 146: 2455–2460; Van der Vlugt et al. (2000) Plant Disease 84: 103; Van der Vlugt et al. (2002) Bulletin OEPP/EPPO Bulletin 32: 503–508). Moreover, the high similarity of the different tomato isolates suggests the existence of a common source of infection for the recent outbreaks.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号