Development of simple sequence repeat markers for the classification of the clubroot pathogen <Emphasis Type="Italic">Plasmodiophora brassicae</Emphasis>

Clubroot disease caused by Plasmodiophora brassicae is one of the most serious diseases in cruciferous crops. To classify isolates, we developed simple sequence repeat (SSR) markers for P. brassicae. Twenty-four Japanese isolates were used in this study: 12 isolates of an unknown pathotype from the Kyoto Prefecture, as well as 12 isolates of known pathotypes, including three single-spore lines. From the 12 isolates from Kyoto Prefecture, 11 were classified into either pathotype 2 (three isolates) or 4 (eight isolates). We designed 23 SSR markers based on the P. brassicae genome, of which 11 markers from intergenic regions showed polymorphisms in the 24 isolates. Many haploid isolates belonging to pathotypes 2 and 4 were monomorphic, and typical alleles were detected in some isolates not belonging to pathotype 4. Two bands were detected for eight SSR loci in five isolates, indicating that different genotypes were mixed in these isolates. We constructed a phylogram based on the 11 polymorphic SSRs. Pathotypes 2 and 4 formed a cluster, from which pathotypes 3 and 1 were successively placed. These results strongly suggest a close genetic relationship between isolates in pathotypes 2 and 4, consistent with our finding that isolates in these two pathotypes were found at one collection site. In combination with pathotype classification and other marker systems, the SSR markers can be used for more detailed analyses to improve the control of clubroot disease.     

云南省水稻细菌性条斑病菌的致病型划分和水稻抗性资源的鉴定

 为明确云南省水稻细菌性条斑病菌(Xanthomonas oryzae pv. oryzicola, Xoc)的致病力分化以及不同类型水稻品种对Xoc的抗感特性,通过针刺接种法将云南省8个稻区采集的86株Xoc菌株,接种于6个携带不同抗性基因的水稻鉴别品种(IRBB4、IRBB5、IRBB14、IRBB18、IRBB21和IR24)。根据这些菌株在鉴别品种上的毒力差异进行了UPGMA聚类分析,将其划分为9个致病型(Ⅰ型 ~ Ⅸ 型)。其中,Ⅰ型为优势菌群,分布频率为50.5%。对不同稻区的优势菌群进行分析,发现云南省各稻区Xoc的致病型呈多样性分布,以强毒力的Ⅰ型为高频率致病型。选用 Ⅰ 型、Ⅱ 型和 Ⅵ 型代表菌株对云南省的80个主栽和区试水稻品种进行抗性评价,对3个致病型表现抗性的材料比例分别为30.0%、35.0%和57.5%。筛选出9个对3种致病型都表现为抗性的品种,其中“Deyou16”和“Changgui2”表现为高抗。研究结果可为云南省防治水稻细菌性条斑病的水稻区域性布局和抗性品种的利用提供理论依据。     

Pathotypic variation in turnip mosaic virus with special reference to European isolates

A collection of 124 isolates of turnip mosaic virus was gathered from around the world, principally from European countries, and characterized by inoculation to four differential lines of Brassica napus (oilseed rape and swede). Three symptom phenotypes were induced—apparent immunity, local infection only, or systemic infection. Twelve distinct patterns, i.e. pathotypes, were observed. Three pathotypes were predominant in the collection; pathotype 1 isolates, which were the most common, did not overcome any of the most extreme sources of resistance in the differential lines. Of the other two, pathotype 3 isolates overcame one of the major sources of resistance and pathotype 4 isolates overcame all sources of resistance. The distribution of pathotypes within Europe was examined. No pathotype was confined to any geographical area, although pathotype 4 isolates were not found in southern Europe or Asia. Most isolates (90) originated from Brassica hosts, while others were from other cruciferae genera (19) or non-crucifers (5). The species of plant that the isolates originated from was not clearly related to the pathotype of the isolates. Resistance to pathotype 1 isolates is controlled by a dominant allele in one of the differential lines, and resistance sources are being examined in the other lines. Isolates belonging to pathotype 1 appeared to be able to mutate readily to overcome the resistance in one of the rape differential lines, but no isolates appeared to mutate to overcome the other major source of resistance in the differentials. The implications of the results for disease control strategies are discussed.     

华南及菲律宾稻白叶枯病病原菌株致病性比较研究

 用国际鉴别寄主及中国鉴别寄主分别在华南及菲律宾两地,同时多次重复研究、比较、分析两地的稻白叶枯病病原菌株的致病力。用人工剪接法测定明确了中国及菲律宾的病情分级调查记载标准呈显著相关,均能反映华南与菲律宾的病情调查实际结果。对4个菲律宾和5个华南菌群而言,"金南风"及"脱脱普"全感,而"早生爱国3号"和"爪哇14号"则全抗。"黄玉"对华南菌群Ⅰ及Ⅱ抵抗,但对Ⅲ及Ⅳ群与4个菲律宾菌群则全感。"IR8"及"Cas209"对5个华南菌群全感,而"DV85"则全抗。"IR20"及"IR1545-339"抗华南菌群Ⅰ、Ⅱ、Ⅲ及Ⅳ,但感染Ⅴ群。"TN1"及"金刚30"等品种全部感染华南及菲律宾菌群。"IR26"抗华南菌群Ⅰ、Ⅱ、Ⅲ、Ⅳ和菲律宾菌群Ⅰ,但感染华南菌群Ⅴ和菲律宾菌群Ⅱ、Ⅲ、Ⅳ。试验结果指出:华南菌群Ⅲ、Ⅳ的,致病力与菲律宾菌群Ⅰ相仿,而华南菌群Ⅴ则与菲律宾菌群Ⅳ相类似。此外,还研究比较分析了华南菌株与东南亚菲律宾、泰国和印度尼西亚诸国菌株间的致病力的异同情况。     

Suggestions for Determination and Terminology of Pathotypes and Genes for Resistance in Cyst-forming Nematodes, especially Heterodera avenae1

A short review of differentiation into pathotypes is given. Use of the word ≪ pathotype ≫ is recommended when a very clear difference is established between virulence of nematode populations. Our present knowledge makes it possible to differentiate between 10 pathotypes of Heterodera avenae. It is suggested that the pathotypes are given numbers, and corresponding terms should be used for genes for resistance in plants, e.g. a gene Hal on the barley chromosome gives resistance to nematode pathotypes 11,21,31,41 etc. Some proposals for improvement of pathotype identification are given.     

Competition and interactions among stripe rust pathotypes in wheat-cultivar mixtures

A series of experiments was conducted with wheat stripe rust to analyse competition between simple and complex pathotypes in host mixtures. Two different pathotype combinations were tested, with different host components. Each combination included a complex (able to infect two host components) and two simple pathotypes. For one of the combinations, induced resistance was tested in a separate experiment as a possible interaction among pathotypes. Disease severity and pathotype frequencies were measured three times during the epidemic, on each host component grown in pure stands and in mixtures. In one of the experiments, pathotype frequencies were also measured within secondary foci. One of the complex pathotypes appeared to have a low fitness on one of the host components and did not significantly increase in frequency in host mixtures relative to pure stands. The average frequency of the other complex pathotype increased during the first epidemic cycles, but remained stable afterwards, below expected values. The results suggest that the development of complex pathotypes in host mixtures may be influenced by differential aggressiveness on the host components, by induced resistance and by random effects resulting from the formation of disease foci, and depends on pathogen autoinfection rate and dispersal mechanisms.     

Characterization of Verticillium dahliae Isolates from Potato on Hokkaido by Random Amplified Polymorphic DNA (RAPD) and REP-PCR Analyses

Verticillium dahliae isolates from potato on the island of Hokkaido (potato isolates) and those belonging to pathotypes A (eggplant pathotype), B (tomato pathotype) and C (sweet pepper pathotype) were divided into three distinct groups by RAPD and REP-PCR. The three DNA groups I, II, III consisted of pathotypes A and C, pathotype B and potato isolates, respectively. The potato isolates were assigned to pathotype A on the basis of pathogenicity. Another set of potato isolates was further collected from eight potato cropping regions on Hokkaido to further examine the relationships among them in detail. Only one of these isolates was identified as DNA group II, but all the others were classified as DNA group III. Isolates from daikon, eggplant, and melon on Hokkaido also belonged to DNA group III. These results suggest that V. dahliae isolates from Hokkaido are unique at the DNA level and different from other pathotype A isolates in Japan. Received 28 February 2000/ Accepted in revised form 6 November 2000     

A selective survey of potato cyst-nematode pathotypes in Great Britain

One hundred and forty-four samples of potato cyst-nematodes, the majority chosen to contain G. pallida , from England, Wales and Scotland were identified to pathotype. Where G. rostochiensis was present it proved to be pathotype Rol, there being no indication of other pathotypes of this species. Of G. pallida , a minority of samples incorporated pathotype Pa 1; many were pathotype Pa3 but distinction between Pa2 and Pa3 was unsatisfactory in many more. It is concluded that recognition of these latter two pathotypes is of little value. The proposed pathotype New Leake could not be recognized.     

Resistance to Turnip mosaic virus in Brassica rapa and B. napus and the analysis of genetic inheritance in selected lines

Forty-two Brassica rapa and Brassica napus lines were tested for resistance to Turnip mosaic virus (TuMV) isolates representing the three major pathotypes in Europe. Of these lines, 11 were susceptible to all pathotypes; nine were resistant to one pathotype; eight were resistant to two pathotypes; and 14 were resistant to all three pathotypes. Of the lines tested, 23 were either able to, or had the potential to, discriminate between two different pathotype-3 isolates. Genetic models for inheritance of resistance were proposed for four B. rapa lines: Jong Bai No. 2 had dominant resistance to pathotype 1 conferred by a single allele; PI418957C and Jin G 55 had recessive resistance to pathotype 4 where a single allele was required; PI418957C also had recessive resistance to pathotype 3 where a model with one of two epistatic, unlinked loci was proposed. Jong Bai No. 1 also had recessive resistance to pathotype 3, apparently conferred by alleles at three loci, where any two of the three loci were epistatic and required for resistance.     

Variation in aggressiveness is detected among Puccinia triticina isolates of the same pathotype and clonal lineage in the adult plant stage

Puccinia triticina reproduces asexually in France and thus individual genotype is the unit of selection. A strong link has been observed between genotype identities (as assessed by microsatellite markers) and pathotypes (pools of individuals with the same combination of qualitative virulence factors). Here, we tested whether differences in quantitative traits of aggressiveness could be detected within those clonal lineages by comparing isolates of identical pathotype and microsatellite profile. Pairs of isolates belonging to different pathotypes were compared for their latent period, lesion size and spore production capacity on adult plants under greenhouse conditions, with a high number of replicates. Isolates of the same pathotype showed remarkably similar values for the measured traits, except in three situations: differences were obtained within two pathotypes for latent period and within one pathotype for sporulation capacity. One of these differences was tested again and confirmed. This indicates that the average aggressiveness level of a leaf rust pathotype may increase without any change in its virulence factors or microsatellite profile.     

甘肃和内蒙古地区马铃薯晚疫病菌的致病型

利用来自国际马铃薯中心含有单显性抗性基因的11个鉴别寄主,采用离体叶片测定方法对2007—2008年采自甘肃和内蒙古地区的共91个致病疫霉马铃薯分离物的致病型进行了测定。结果显示：来自甘肃的65株菌中共有28个致病型,有3株可以克服11个抗性基因;总共有超过一半的菌株对抗性基因R7、R9、R11有毒性,而能克服抗性基因R1、R2、R8的菌株数最少。在来自内蒙古的26株菌中,共检测到24个致病型,有2株菌能克服11个抗性基因,共有84.6%的菌株可以对含有抗性基因R7的植株表现出毒性,而R1、R2、R8被克服比例最低。因此,研究结果表明,在这两个地区可优先考虑在菌株采集地种植和选育含有R1,R2和R8这3个抗性基因的马铃薯品种。     

Electrophoretic karyotype variation among pathotypes of Fusarium oxysporum f.sp. dianthi

Karyotype analysis by pulsed-field gel electrophoresis was applied to characterize isolates of Fusarium oxysporum f.sp. dianthi , the causal agent of Fusarium wilt on carnation. Eleven distinct chromosomal DNA patterns were detected among 38 pathogenic isolates, and the total genome size was estimated to range from 23·7 to 36·4 Mb. Except for isolates belonging to pathotypes 2 and 4 , all members of the same pathotype shared overlapping electrophoretic karyotypes. Karyotypes of isolates assigned to pathotypes 1 and 8 showed a high degree of similarity, in accordance with VCG and RFLP analysis. The same electrophoretic karyotype was also shared by members of pathotypes 2 and 5, thus confirming results obtained by both VCG and RFLP grouping, A single representative of pathotype 6, previously confined to the same VCG and RFLP group as pathotypes 2 and 5, had a slightly different chromosomal pattern. Isolates assigned to pathotype 4 showed four related karyotypes which partially differed in both the number and size of chromosomal bands. However, all strains assigned to this pathotype shared a basic profile of nine chromosomal bands, while two low-molecular-weight bands were present or absent. The findings are discussed with regard both to the suitability of race distinction in the case of the special form dianthi of F. oxysporum and to the use of karyotype analysis by PFGE as a tool for the study of the population genetics of this fungus.     

Studies on the origin,spread, and evolution of an important group ofPuccinia recondita f. sp.tritici pathotypes in Australasia

Wheat brown rust pathotype (pt) 104-2,3,(6),(7), 11 was first detected in Australasia in Victoria during 1984. Although it appeared similar to a pre-existing pathotype, 104-2,3,6,(7), detailed greenhouse test revealed nine pathogenic differences between the two rusts. Six differences involved contrasting virulence/avirulence for the resistance genes/specificitiesLr12, Lr27+Lr31 andLr16, and three uncharacterised genes, present in the wheat cultivars Gaza and Harrier, and in triticale cultivar Lasko. Differences in partial virulence between the pathotypes were found for the genesLr2a, Lr13 andLr26. A comparison of the phenotypes for 13 isozyme systems in the two pathotypes revealed two differences, including aPgm2 allele in pt 104-2,3,(6),(7),11 not found in other contemporary AustralasianPuccinia recondita f. sp.tritici pathotypes. On the basis of these differences, it was concluded that pt 104-2,3,(6),(7),11 was introduced into the Australasian region before or during 1984.Seven variants of pt 104-2,3,(6),(7),11, that differed by single virulences, were detected during 1984–1992. Pt 104-2,3,(6),(7),11 and a derivative pathotype with virulence forLr20 underwent rapid increases in frequency, largely displacing pathotypes which predominated before 1984. Although first detected in eastern Australia, both pathotypes spread to New Zealand, and the derivative pathotype appeared in Western Australia. The rapid spread and increase of these pathotypes could not be explained by host selection. Pt 104-2,3,(6),(7),11 and derivatives may therefore be more aggressive than other contemporary Australasian pathotypes.Abbreviations NSW New South Wales - Prt Puccinia recondita f. sp.tritici - Qld Queensland - SA South Australia - WA Western Australia     

Pathotypes of Synchytrium endobioticum in Germany

Results are given of a survey on the occurrence of pathotypes (races) of Synchytrium endobioticum (potato wart) in both parts of re-unified Germany. An assortment of six differential cultivars appears to be sufficient to distinguish between the seven presently important German wart pathotypes. A total of ten pathotypes was recorded. Two West and two East German pathotypes seem to be identical, based on the results obtained with presently available cultivars. In contrast to pathotype 1 (common race) which prior to 1945 was distributed over the whole German territory, the 'new' pathotypes seem to prefer the central and south German mountain areas.     

华南水稻白叶枯病菌致病性分化检测与分析

为了解华南稻区水稻白叶枯病菌的致病性分化和变异动态,采集华南地区水稻白叶枯病病叶标样分离病原菌,应用中国鉴别寄主IR26、南粳15、爪哇14、特特普、金刚30和国际水稻已知抗病基因的近等基因系IRBB5、IRBB13、IRBB3、IRBB14、IRBB2、IR24两套鉴别寄主,在水稻孕穗期采用剪叶法接种,依据寄主和菌株的互作反应检测病菌的致病性分化。结果显示,参试菌株可划分为Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ、Ⅸ六个致病型和R1、R2、R3、R4、R5、R8、R10七个致病小种。Ⅴ、Ⅳ致病型和R8、R5小种出现频率分别为27.40%、19.30%和44.67%、15.34%,为华南稻区优势种群。Ⅸ、Ⅴ、Ⅳ致病型和R8、R5小种对500份华南稻区品种资源的致病率依次为96.40%、95.00%、50.40%、62.00%和42.60%;Ⅸ致病型毒性最强且发展很快;强致病菌系Ⅴ型已替代Ⅳ型发展为华南优势致病菌系。     

Problems of potato cyst nematode pathotypes in the Czech Republic

During 1983–1989 about 1,200 infested plots in the Czech republic were investigated for the occurrence of new pathotypes of the potato cyst nematodes (PCN) Globoderu rostochiensis and G. pallida. Only eight populations of the pest were suspected of containing another pathotype than Ro1. Glasshouse pot trials were performed with those eight natural populations, two populations of Ro1, 10 potato cultivars resistant to Ro1 and 10 cultivars resistant to more pathotypes, G. pallida included. The multiplication rates (Pf/Pi) showed that four of the PCN populations were probably mixtures, with pathotype Ro1 prevailing. Three populations were suspected of containing G. pallida , but their morphological characters corresponded only with G. rostochiensis. One population corresponded with pathotype Ro5. The extent of the occurrence of pathotypes or virulence groups different from Ro1 can be estimated at 0.3–0.4% of infested plots.     

Development of a Pathotype Specific SCAR Marker in Plasmodiophora brassicae

Plasmodiophora brassicae is an obligate biotroph that causes clubroot, one of the most damaging diseases of crucifers. Breeding of clubroot-resistant plants has been hampered by the large variation of pathogenicity in P. brassicae and by the lack of an efficient means for detecting specific isolates. To improve the practicality of P. brassicae pathotype-identification, a molecular approach was developed. RAPD profiles of 37 single-spore-derived isolates belonging to seven different pathotypes were compared. A RAPD marker, OPL14₁₂₀₀, was found in the molecular pattern of all the isolates belonging to one particular pathotype (P1), pathogenic on all differential hosts tested. The DNA band corresponding to this marker was cloned and sequenced. No significant homology to previously characterised nucleotide sequences was found. Primers were designed to specifically amplify the OPL14₁₂₀₀ band. The SCAR marker was observed in all isolates belonging to pathotype P1 and was absent in isolates belonging to other pathotypes and in the different plant hosts analysed. The SCAR marker was also generated from direct amplification of DNA from clubs (mixture of host and pathogen DNA) developed after infection by P1 isolates. This molecular marker may be a valuable tool for rapid and reliable identification of P. brassicae P1 isolates in areas where resistant varieties are cultivated.     

水稻对白叶枯病强毒菌系Ⅴ型菌的抗性研究

作者报道了水稻对广东白叶枯病强毒菌系Ⅴ型菌抗性研究与抗源筛选评价结果。从1076份国内外水稻种质资源中筛选出29份抗病材料,占2.70％。其中IRBB7等5份具有广谱、高抗兼较好农艺性状。由日本和国际水稻所鉴定的14个抗性基因中Xa-3、xa-5、Xa-7、xa-13等抗Ⅴ型菌。抗Ⅴ型菌材料多数兼抗其它菌型,但亦有一些不抗Ⅳ型菌,表明菌型与品种间有强烈互作效应。水稻对Ⅴ型菌抗性与其类型有关,梗稻与籼稻、糯稻与粘稻、国外稻与国内稻比较,抗病率均以前者为高。     

Relation between pathogenicity and genetic variation within <Emphasis Type="Italic">Plasmodiophora brassicae</Emphasis>

The relation between diversity of pathogenicity on clubroot-resistant (CR) cultivars of Chinese cabbage (Brassica rapa subsp. pekinensis) bred in Japan and DNA polymorphisms in 17 populations of Plasmodiophora brassicae from cruciferous plants was examined by inoculation tests and random amplified polymorphic DNA (RAPD) analysis using 18 arbitrary primers. Four pathotypes (A–D) were identified after inoculation of six CR cultivars of Chinese cabbage in the 17 populations from cruciferous crops. A relatively high level of genetic diversity was also detected among these populations in the RAPD analysis. Although the four pathotypes could not be clearly differentiated using the RAPD data, most populations of three pathotypes had a consistent location on the dendrogram. All pathotype B (virulent on five cultivars except Utage 70) and D (avirulent on all cultivars) populations, which were common in incompatible interactions with cv. Utage 70, were located in a single subcluster. All five pathotype C populations (virulent only on cv. Utage 70) except for one population grouped in another single subcluster. Because four pathotype A populations (virulent on all six cultivars, races 4 and 9) fell in different subclusters, the populations may be genetically polyphyletic. Populations from cruciferous weed Cardamine flexuosa differed remarkably from those from cruciferous crops in pathogenicity on common cultivars of Chinese cabbage and turnip and C. flexuosa, but they grouped in a single cluster with all race 9 populations from crops. Race 9 populations from crops may thus be closely related to populations from the weed rather than to races 1 and 4 from crops.