Characterization of Glomerella cingulata isolates from almond fruit using VCG,molecular, fungicide sensitivity and pathogenicity tests 1

Almond anthracnose caused by Glomerella cingulata is a major disease of this crop in Israel. The pathogen infects young fruit resulting in fruit rot. Leaf wilting and shoot dieback accompany fruit rot, even though the pathogen cannot be isolated from leaves or twigs. Isolates of G. cingulata from diseased almond fruit were compared using vegetative compatibility grouping (VCG), molecular methods, fungicide sensitivity and pathogenicity assays in order to determine the genetic diversity and host specificity among different populations. Polymerase chain reaction amplification of genomic DNA, using four primers produced uniform banding patterns for all the almond isolates from different geographic locations in Israel. HaeIII digestion patterns of A + T-rich DNA, and Southern hybridization of the repetitive nuclear DNA element (GcpR1) to PstI-digested genomic DNA of almond isolates also revealed no polymorphism. Chlorate-resistant nitrate-nonutilizing (nit) mutants were generated and used in heterokaryon tests. Complementary heterokaryons formed between the mutants of different isolates indicated a single VCG. Isolates of G. cingulata from almond had optimal growth temperatures of 20–22°C as opposed to 26–28°C for avocado isolates. In addition, almond isolates of G. cingulata are insensitive to benzimidazole fungicides in contrast to sensitivity of isolates from avocado. In artificial inoculations, almond isolates infected almond, avocado, apple, mango and nectarine fruit at a slower rate than G. cingulata isolates from avocado, apple and mango. Only the anamorph Colletotrichum gloeosporioides has been detected on almond in Israel, whereas isolates of G. cingulata from other hosts produce ascocarps.     

Coffee berry disease in Kenya. II. The role of Glomerella cingulata in the Colletotrichum population,colonizing the bark of Coffea arabica

On the maturing bark of cut branches ofCoffea arabica previously sprayed with copper fungicides perithecia ofGlomerella cingulata were easily found after two to ten days of incubation. Without fungicides the number of perithecia was decidedly lower. On prunings left on the ground under the coffee trees for 6 to 24 weeks the perithecia could also be found, but the numbers declined rapidly with time. Perithecia ofG. cingulata could forcibly discharge ascospores under laboratory conditions. Monospore cultures obtained by catching ascospores on agar, invariably belonged to threeColletotrichum types. It was rarely possible to isolate aColletotrichum able to infect green coffee berries. Growthrate, colour of the mycelium, number of conidia producedin vitro and infectivity on green coffee berries, however, differed substantially fromC. coffeanum, the cause of coffee berry disease. In Kenya no evidence has been obtained that ascospores from perithecia on bark could infect wounded or unwounded green coffee berries. Neither has any infection been obtained with ascospores from perithecia grownin vitro. Possible explanations for the difference with previous findings are offered. Based on the data presented in this paper, it is concluded thatG. cingulata is not likely to play a role in the epidemiology of the coffee berry disease in Kenya.     

Pathogenicity,colony morphology and diversity of isolates of <Emphasis Type="Italic">Guignardia citricarpa</Emphasis> and <Emphasis Type="Italic">G. mangiferae</Emphasis> isolated from <Emphasis Type="Italic">Citrus</Emphasis> spp.

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.     

Variability of Cuban and International Populations of Alternaria solani from Different Hosts and Localities: AFLP Genetic Analysis

As causal agent of early blight disease in tomato and potato, Alternaria solani is an internationally important horticultural pathogen. Genetic variability was surveyed by amplified fragment length polymorphism analysis in a total of 112 isolates from potato and tomato, representing pathogen populations from different Cuban provinces together with isolates from the USA, Brazil, Turkey, Greece and China. Also included in the analysis were isolates from catenulated Alternaria spp. from Brazil, Canada, Greece and Russia, along with single isolates of Alternaria porri, Alternaria alternata and a Curvularia sp. UPGMA clustering revealed a differentiation between the isolates of A. solani and all other species with the exception of A. porri which could not be distinguished from A. solani. Among the isolates of A. solani, two distinct subclusters were formed, with high genetic significance revealed by bootstrapping, corresponding to a general subdivision based on the respective solanaceous host. The results are discussed with regard to potential host specificity of A. solani on tomato and potato, and in terms of the comparative contributions of regional and international genetic variability in populations of this ubiquitous plant pathogen.     

Genetic Structure of the Population of Phytophthora infestans Attacking Solanum ochranthum in the Highlands of Ecuador

Thirty-nine isolates of Phytophthora infestans were collected from the wild host Solanum ochranthum in the highland tropics of Ecuador and characterized with a set of phenotypic and molecular markers (mating type, metalaxyl sensitivity, the allozyme loci Gpi, and Pep, mitochondrial DNA haplotype, RFLP, and SSR), as well as for pathogenicity on various hosts. Three groups of isolates (A, B, and C) were identified based on their multilocus genotypes and variable abilities to cause disease on different hosts. Group A had a combination of alleles for the Gpi (86/100), Pep (96/100) and mtDNA (Ia) loci, as well as an RFLP fingerprint, that have not been reported for P. infestans in Ecuador, or elsewhere. Group B shares many marker characteristics with the US-1 lineage described in Ecuador on tomato, pear melon (S. muricatum), and S. caripense, but has SSR alleles not present in typical US-1 isolates. Group C for all markers tested is identical to the EC-1 lineage described on cultivated and wild potatoes in Ecuador. All isolates from S. ochranthum were able to re-infect their host of origin in the detached leaf assay; however, we did not draw clear conclusions as to the relative aggressiveness of the three groups on this host. Isolates of group A were the most specialized and were generally non-pathogenic or weakly pathogenic on all hosts other than S. ochranthum. Groups B and C infected tuber-bearing hosts, including the cultivated potato but were generally non-pathogenic on other non-tuber bearing hosts. Solanum ochranthum was infected by isolates coming from tuber-bearing Solanum hosts (i.e., the EC-1 lineage of P. infestans) and some US-1 isolates from non-tuber bearing hosts. Thus, in nature this species might be a potential reservoir of inoculum of different pathogen populations able to infect the cultivated hosts potato, tomato and pear melon (S.␣muricatum). Unlike potato and tomato in Ecuador, each of which is primarily attacked by a highly specialized pathogen population, S. ochranthum appears to harbour at least three pathogen groups of␣different genetic make-up. The unresolved issue of potential host specificity in isolates found on S.␣ochranthum could complicate efforts to use this species in tomato improvement.     

Mating type, pathotype and RAPDs analysis inDidymella rabiei, the agent of ascochyta blight of chickpea

Eleven pathotype groups (A-K), including five not previously reported, ofDidymella rabiei (anamorphAscochyta rabiei), representing isolates of the pathogen from Ascochyta blight-affected chickpeas mainly from India, Pakistan, Spain and the USA, were characterized using 44 single-spore isolates tested against seven differential chickpea lines. Of 48 isolates tested for mating type, 58% belonged to MAT 1-1 and 42% to MAT 1-2. Thirty-nineD. rabiei isolates, as well as two isolates ofAscochyta pisi and six isolates of unrelated fungi, were analyzed using Randomly Amplified Polymorphic DNAs (RAPDs) employing five primers (P2 at 40°C, and OPA3, OPC1, OPC11 and OPC20 at 35°C). Computer cluster analysis (UPGMA / NTSYS-PC) detected a relatively low level of polymorphism among all theD. rabiei isolates, although atca 7% dissimilarity,ca 10 RAPD groups [I-X] were demarcated, as well as subclustering within the larger groups. By the same criteria, the maximum dissimilarity for the whole population ofD. rabiei isolates wasca 13%. No correlation was found between different RAPD groups, pathotype, or mating type ofD. rabiei, although some evidence of clustering based on geographic origin was detected. The use of RAPDs enabled us to identify specific DNA fragments that may have a potential use as genetic markers in sexual crosses, but none which could be used as virulence markers.     

Analysis of a Secreted Aspartic Peptidase Disruption Mutant of Glomerella cingulata

Peptidases have been implicated in the pathogenicity of fungi that cause disease in plants. Expression of the secreted aspartic peptidase gene (gcsap), of a Glomerella cingulata isolate pathogenic on apples, is induced during appressorium formation. To determine whether the secreted aspartic peptidase (GcSAP) is essential to pathogenicity, gcsap was disrupted using a vector containing a 637 bp fragment of genomic DNA that encodes the sequence spanning the two active site aspartic acid (Asp) residues. To ensure that the truncated gcsap gene products could not have residual peptidase activity the codons for the active site residues Asp¹¹² and Asp²⁹⁷ were both mutated to histidine residues. Both PCR and Southern analysis confirmed disruption of gcsap. Neither gcsap mRNA nor GcSAP activity was detected in the disruption mutant. Pathogenicity tests on fruit from three apple cultivars showed that GcSAP was not required for pathogenicity. The disruption mutant grew on medium containing protein as the sole source of nitrogen because G. cingulata secretes a previously undetected peptidase(s). A serine peptidase that had a pH optimum between pH 7.0 and 8.0 and a K _m of 0.25 mM for the synthetic substrate succinyl-Ala–Ala–Pro–Phe-p-nitroanilide was identified.     

Differentiation of Bean pod mottle virus isolates based upon host symptoms

Accessions from Glycine, Phaseolus, and Vigna genera were screened for their reactions to different subgroups of isolates of Bean pod mottle virus (BPMV) in order to establish a differential host system. Screening results indicated that the BPMV isolates differed in pathogenic aggressiveness but not in virulence. No major resistance genes were found in soybean (Glycine max) or G. soja since all screened accessions showed mosaic or necrotic symptoms to BPMV inoculation. However, these accessions expressed differences in severity of symptoms when challenged by various BPMV isolates. The inoculation of G. tomentella accessions did not result in mosaic symptoms, and some accessions did not support systemic infection of some of the isolates. Resistance, presented as a hypersensitive reaction, was observed in some of Phaseolus and Vigna genotypes, and resistant response or susceptibility was stable to all the isolates used in the screening. In conclusion, the selected G. soja genotypes PI 407019, PI 464889A, and PI 464928, and ‘Amsoy 71’ soybean may help to separate severe (reassortant) from mild isolates of BPMV based upon their phenotypic reactions.     

Cultural characteristics, pathogenicity and genetic diversity of Fusarium oxysporum isolates from tobacco fields in Spain

Several formae speciales of Fusarium oxysporum are capable to produce disease in tobacco plants. Different authors have classified those isolates as a forma specialis or a race within on the basis of the severity of disease and host specificity. Fusarium wilt of tobacco plant in Extremadura (central Spain) tobacco fields have been recorded in the last years and F. oxysporum was isolated from symptomatic plants. The aim of our study was to characterize these F. oxysporum populations. For this purpose, the in vitro spore production and growth and the virulence (severity of disease) have been tested. Although all isolates behaved as pathogen, the virulence of isolates was different. The differences in growth could not be correlated with other characteristics but the two isolates with scarce spore production have also behaved as the weakest pathogen. We have analyzed intergenic spacer (IGS) region polymorphism of ribosomal DNA and random amplified polymorphic DNA (RAPD) markers to assess the genetic diversity within F. oxysporum isolates. These molecular analyses showed two major groups with different physiological capabilities that could reflect two different lineages. One group was characterized by medium–high sporulation, high virulence and the same IGS-RFLP pattern. The other group was more heterogeneous featuring low–medium sporulation and variable virulence and growth. This first experimental approach to pathogen population could be a good starting point for further studies including non-pathogenic isolates and a larger number of pathogen that could clarify if there are two or more genetic lineages.     

呼和浩特市苜蓿根腐病病原菌鉴定及致病性测定

为确定引起呼和浩特市苜蓿根腐病的病原菌种类,采用常规组织分离法对采集的疑似苜蓿根腐病病样进行病原菌分离与培养,利用形态学观察结合分子生物学方法对分离物代表菌株进行鉴定,并采用土壤接种法对代表菌株的致病性进行测定。结果表明,共分离获得6类形态学特征不同的分离物,各随机选择1株代表菌株进行鉴定,结合分子生物学鉴定结果确定呼和浩特市苜蓿根腐病病原菌有6种,分别是麦根腐平脐蠕孢菌Bipolaris sorokiniana、立枯丝核菌Rhizoctonia solani、木贼镰刀菌Fusarium equiseti、变红镰刀菌F. incarnatum、锐顶镰刀菌F. acuminatum和织球壳枯萎菌Plectosphaerella cucumerina,分别分离到1、7、14、26、7和14株菌株,占总分离菌株数的1.45%、10.14%、20.29%、37.68%、10.14%和20.29%。其中,立枯丝核菌的致病力最强,接种苜蓿幼苗发病的病情指数达82.67,其次为木贼镰刀菌、变红镰刀菌、锐顶镰刀菌、麦根腐平脐蠕孢菌和织球壳枯萎菌,病情指数分别为72.67、62.67、58.67、52....     

A comparison of morphology,pathogenicity and restriction fragment patterns of mitochondrial DNA among isolates of Phytophthora porri Foister

Thirteen strains ofPhytophthora porri from five different hosts were compared with respect to their morphology, cardinal temperatures for growth, pathogenicity to leek and cabbage and restriction fragment patterns of mitochondrial DNA. Morphology of vegetative growth was rather similar in most isolates. Those characters which differed among isolates showed overlapping variability and could not be used to distinguish groups, with the exception of production of oogonia and sporangia and the antheridium type. Considerable differences were found in restriction patterns of mitochondrial DNA, isolates from the same host mostly showing identical patterns. Isolates from differentAllium species showed relatively similar restriction patterns if compared to the other isolates. Isolates fromBrassica oleracea proved to be a homogeneous group, quite different from the others with respect to restriction patterns, production of sporangia, production of oogonia, antheridium type and pathogenicity. One isolate, CBS 366.59, isolated from and pathogenic toA. porrum, deviated in many characters from the other isolates. It showed the restriction patterns ofPhytophthora nicotianae and also the high cardinal temperatures for growth typical for this species. The sporangia, however, were distinctly non-papillate and the majority of antheridia was of the paragynous type.     

Biological control ofBotrytis cinerea in residues and flowers of Rose (Rosa hybrida)

Microbial isolates from living petals, petal residues and leaf residues of rose, and from laboratory collections, were evaluated for control ofBotrytis cinerea in rose. In leaf residues artificially infested withB. cinerea, isolates of the filamentous fungiGliocladium roseum, FR136 (unidentified) andTrichoderma inhamatum reduced sporulation of the pathogen by >90%, other filamentous fungi were 25–90% effective, and those of yeasts and bacteria were <50% effective. In artificially inoculated petal residues, no microbe reduced sporulation ofB. cinerea by >75%, but isolates ofCladosporium oxysporum and four yeasts were 51–75% effective, and three filamentous fungi, eight yeasts andBacillus subtilis isolates were 26–50% effective. Isolates ofT. inhamatum, C. oxysporum andG. roseum performed best againstB. cinerea among isolates evaluated in leaf residues naturally infested with the pathogen and indigenous microorganisms. Totals of ten isolates of filamentous fungi (includingC. oxysporum andC. cladosporioides), two of yeasts and five ofBacillus subtilis completely prevented lesion production byB. cinerea in detached petals, and a further six isolates of filamentous fungi (includingG. roseum) and six yeasts were 90–99% effective. Isolates ofC. oxysporum, C. cladosporioides andB. subtilis, the most effective microorganisms againstB. cinerea in flower buds, reduced number of lesions in the range of 42–65% compared with 59–89% for à standard fungicide (vinclozolin). It is suggested that application of leading antagonists Jo living rose leaves and flowers should optimize control of inoculum production byB. cinerea when the tissues die. Optimal biocontrol of lesion production in flower buds requires a better understanding of the microenvironment of petals.     

Genetic variability and virulence among Verticillium albo-atrum isolates from hop

Verticillium wilt, caused by Verticillium albo-atrum or V. dahliae, is an important disease of many worldwide crop species. In Europe, V. albo-atrum isolates infecting hop express different levels of virulence, inducing mild or lethal disease syndromes, and it is therefore an attractive model for studying the virulence of this pathogen. In this work, eleven amplified fragment length polymorphism (AFLP) primer combinations were used to analyze genetic variability among 55 V. albo-atrum hop isolates from four European hop growing regions, as well as isolates from other hosts and V. dahliae isolates. Cluster analysis divided V. albo-atrum and V. dahliae isolates into two well-separated groups. Within the V. dahliae cluster, isolates were separated without host specific grouping, although no host adapted isolates were included. In V. albo-atrum, the alfalfa isolates were distinct from isolates of other hosts, where a high association with virulence was observed in hop and tomato isolates. All lethal hop isolates were genetically different from mild hop isolates. The lethal hop isolates from England and Slovenia expressed the same virulence phenotype, although they showed a different AFLP pattern. The mild hop isolates formed two subgroups, to which isolates clustered irrespective of geographical location. These data suggest multiple origins of V. albo-atrum hop isolates, and the possible appearance of new virulent isolates in the future in other hop growing regions.     

Susceptibility of pure and hybrid willows to isolates ofMelampsora epitea rust

Pure species and F₁ hybrid families ofSalix viminalis andS. dasyclados were tested for resistance to four single uredinium isolates ofMelampsora rust in laboratory experiments using excised leaves. Rust isolates were derived from:S. viminalis, S. dasyclados, aS. viminalis x triandra hybrid, andS. daphnoides. Incidence of infection, number of uredinia per leaf, and numbers of spores per uredinium were measured. As expected, the isolate fromS. daphnoides did not infect any of the willow species or hybrids tested. For the other three rust isolates that were tested, the parent from which the isolate was derived was susceptible, the other parent was resistant, and hybrids were intermediate in resistance for incidence and uredinia per leaf. These patterns indicate additive inheritance of these resistance traits in hybrids. Numbers of spores per uredinium were similar on the hybrids and the susceptible parent for one rust isolate, suggesting dominant inheritance of this trait in the hybrids.     

Selection and evaluation of phyllosphere yeasts as biocontrol agents against grey mould of tomato

Phyllosphere yeasts antagonistic to the infective activity of Botrytis cinerea were isolated from leaves of greenhouse-grown tomatoes and evaluated in a detached leaf assay for their ability to suppress grey mould. Nine of 30 recovered yeast isolates were found to reduce a disease index by >90% when compared to an untreated control. In greenhouse experiments, the yeast isolate Rhodotorula glutinis Y-44 was the most efficient in controlling grey mould of tomato plants. In further experiments in greenhouse-grown tomato plants the effectiveness of R. glutinis Y-44 was compared with two commercial fungicides. It was demonstrated that R. glutinis Y-44 was as effective as fungicides in controlling the pathogen. Moreover, the population of R. glutinis Y-44 was monitored for 8 weeks after application on tomato plants. The isolate successfully colonized the plant surface, although the population decreased by 10-fold 8 weeks after application. Since B. cinerea is also a major post-harvest pathogen for tomato fruits, the ability of R.␣glutinis Y-44, to protect artificially infected wounded tomato fruits was also tested. It was shown that R.␣glutinis Y-44 was able to reduce by 50% the percentage of infected wounds compared to the untreated controls.     

Note:In vitro antagonism of actinomycetes isolated from fungus-growing ants against plant pathogenic fungi

Fungus-growing ants have been found recently to be symbiotic with actinomycetes living on the ant’s cuticle; these bacteria are inhibitory to soil fungi that are detrimental to the ants’ fungus gardens. In order to investigate whether actinomycetes found on the cuticle of attine ants also had inhibitory properties against plant pathogenic fungi, we isolated 32 strains of actinomycetes from fungus-growing ants (Atta, Trachymyrmex, andCyphomyrmex), from the Mexican states of Coahuila, Nuevo León and Tamaulipas. Of the actinomycetes tested against selected plant pathogenic fungi (Alternaria solani, Aspergillus flavus, Colletotrichum lindemuthianum, Rhizoctonia solani, Sclerotium sp.) on Czapek-Dox agar medium, 13 isolates inhibited at least one of the fungi.C. lindemuthianum was inhibited by 11 actinomycetes, andRhizoctonia by three. An actinomycete strain isolated fromCyphomyrmex rimosus inhibited all five fungi tested. http://www.phytoparasitica.org posting July 30, 2008.     

Evaluation of morphology of infection structures in distinguishing between different Allium rust fungi

Fifteen isolates of rust fungi were collected in the United Kingdom and in the Netherlands from severalAllium species. The samples represented three putative rust species. The morphology of the telia, teliospores and urediniospores was investigated. From urediniospores infection structures were induced on leek, and their morphology was described. Telia and teliospores were not available on every sample. Morphology of the infection structures clearly differentiated between ‘leek’ type and ‘chive’ type isolates. The morphology of infection structures ofPuccinia mixta is very similar to that ofUromyces ambiguus, but clearly distinct fromPuccinia allii sensu Jennings from leek. Quantitative differences in urediniospore characters differentiated between the putative species, but there was overlap between the taxa. We conclude that morphology of infection structures of urediniosporelings is a useful trait for identification of rust isolates fromAllium. This is especially true where more than one rust species may occur on the same host species, as withAllium fistulosum.     

Gnomonia fragariae, a Cause of Strawberry Root Rot and Petiole Blight

Gnomonia fragariae has been occasionally listed among the fungi associated with diseased strawberry plants. However its pathogenicity has not been established. During the investigation on strawberry decline in Latvia and Sweden, a fungus was repeatedly recovered from discoloured root and crown tissues of severely stunted plants. Attempts to induce sporulation of the isolates grown on several agar media resulted in the formation of mature ascomata only on potato carrot agar and oatmeal agar. On morphological grounds and comparisons with reference herbarium specimens these isolates were identified as Gnomonia fragariae. The pathogenicity of the fungus was evaluated initially in the detached leaf assay and subsequently in three bioassays on strawberry plants. All the bioassays showed that G. fragariae was pathogenic on strawberry and capable of causing severe root rot and petiole blight. The symptoms that developed in the greenhouse experiments closely resembled those observed in the fields. The fungus did not cause rapid plant death but growth and development of inoculated strawberry plants was severely affected. To our knowledge this is the first time when pathogenicity of G. fragariae as a root rot pathogen has been clearly established. Our study shows that G. fragariae is one of the serious pathogens involved in the root rot complex of strawberry in Latvia and Sweden.     

<Emphasis Type="Italic">Teratosphaeria (Mycosphaerella) nubilosa,</Emphasis> the causal agent of Mycosphaerella leaf disease (MLD), recently introduced into Uruguay

Mycosphaerella leaf disease on Eucalyptus is well known in Uruguay but none of the more serious Mycosphaerella spp. and Teratosphaeria spp. causing this disease have yet been found. In the autumn of 2007, more severe defoliation than has been known in the past and associated with symptoms resembling Mycosphaerella infections was observed on Eucalyptus globulus. Isolations and identifications based on morphology and DNA sequence comparisons showed that the causal agent of the defoliation is the well known and serious pathogen Teratosphaeria nubilosa (=Mycosphaerella nubilosa). This is the first record of the pathogen in South America. Using ten microsatellite loci previously developed for T. nubilosa, only one multilocus haplotype was found from 46 T. nubilosa collected isolates. Interestingly, this haplotype was the same as one previously found in Portugal and Spain. The results suggest that T. nubilosa has recently been introduced into Uruguay and that it most likely originated from the Iberian Peninsula where E. globulus is widely planted.     

云南省小麦条锈菌不同地理亚群体的遗传结构分析

为明确云南省小麦条锈菌（Puccinia striiformis f. sp. tritici,Pst）在不同地理环境下的群体遗传结构,通过3种不同地理亚群体划分方式,即以县域（Group C）、区域（Group R）和海拔（Group E）对云南省537个Pst单孢系进行不同层次的群体划分,并利用12对SSR引物对其进行遗传多样性和群体遗传结构分析。结果显示,云南省Pst的遗传多样性水平在Group C的亚群体之间差异最大,且来自滇中及滇东北地区的Pst群体的遗传多样性较高。Group R和Group E的亚群体基因流及遗传分化结果表明,云南省Pst菌源交流频繁、遗传分化较小。系统进化树分析结果显示,滇东北与滇中Pst群体类似,滇东南与滇西Pst群体类似。Pst遗传组分呈现出由东向西、由北向南和自低海拔向高海拔变化的趋势,与云南省自东南向西北逐渐攀升的地形及地势吻合。Mantel检验结果表明地理距离与遗传距离不存在相关性,在8个县域亚群体、2个区域亚群体检测到有性生殖。表明来自滇中和滇东北地区的Pst群体具有更高的遗传多样性,地理隔离可能是滇西地区遗传多样性较低的成因,遗传分化发生在...