西安地区瓜类病毒病的鉴定及防治

西安地区195个瓜类病毒病样的鉴定结果表明,各种瓜类上的病毒为甜瓜花叶病毒(MMV)和黄瓜花叶病毒(CMV)两种。西葫芦、笋瓜、甜瓜、南瓜以及黄瓜上,以引致花叶的MMV为主(一般占90％以上),其次是黄化皱缩病状的CMV。西瓜只有MMV;冬瓜和丝瓜则为CMV。甜瓜和西葫芦上还分离到CMV的一个新株系,西瓜可以作为以上两种病毒的鉴别寄主。     

黄瓜花叶病毒2a基因上的两个氨基酸共同决定其在豆科植物上引发的过敏反应

过敏反应(hypersensitive response, HR)是植物对病原物侵染的一种抗性反应. 对黄瓜花叶病毒(Cucumber mosaic virus, CMV)在豆科植物上引发HR反应的相关因子进行了研究, 证明CMV 2a基因中的243个碱基决定了过敏反应. 进一步对该区域进行了分析和点突变研究, 用豆科系统侵染株系CMV-P1的631位氨基酸酪氨酸(Tyr)替换豆科局部坏死株系CMV-Fny的相应位点氨基酸苯丙氨酸(Phe)后得到的突变体(Fny-F/Y)在豆科植物上引发HR反应, 但过敏枯斑能够向外扩展; 用CMV-P1的641位氨基酸丝氨酸(Ser)替换CMV-Fny的相应位点氨基酸丙氨酸(Ala)得到的突变体(Fny-A/S)在豆科植物上引发的HR反应与CMV-Fny引发的症状没有差异; 当这两个位点同时被置换后得到的突变体(Fny-FA/YS)在豆科植物接种叶上就不再引发HR反应, 而是产生系统侵染, 说明CMV在豆科植物上引发的过敏反应是由CMV 2a基因上的631和641位氨基酸共同决定的.     

侵染番茄的黄瓜花叶病毒（CMV）株系特性的比较研究

从山东省主要番茄种植区病毒样本中分离到111个黄瓜花叶病毒(CMV)分离物,根据病毒的寄主范围和症状,初步鉴定为三个株系:番茄蕨叶株系(CMV-ToF)、番茄花叶株系(CMV-ToM)和番茄轻花叶株系(CMV-ToL)。三株系除在生物学特性存在明显差异外,其病毒粒体形态大小,电泳迁移率,病毒外壳蛋白亚基分子量、核酸组分以及病毒粒体血清学特性亦存在差别。     

马尾松林中球孢白僵菌寄主转移和专化性的SSR标记分析

球孢白僵菌是一种最常见的虫生真菌,已被广泛应用于害虫生物防治。利用SSR简单序列重复(simple sequence repeat,SSR)分子标记对来自安徽省麻姑山马尾松林的102株球孢白僵菌进行基因分型、寄主转移和寄主专化性研究。9对微卫星引物将102株白僵菌分成31个微卫星基因型。在这31个微卫星基因型中,有5种基因型株系为相对优势菌株,这5种基因型株系通过侵染不同寄主昆虫即寄主转移延续自身在马尾松林生态系统中的传播和流行,从而证实寄主转移是白僵菌群体中的普遍现象。同时,这些相对优势基因型并不是在各个月份均匀分布,在大部分月份中,存在1–2种优势度高的基因型。相同基因型株系可侵染不同寄主的结果揭示出白僵菌不仅在种的水平,而且在菌株水平上寄主专化性也较弱。正是白僵菌较弱的寄主专化性特征促使部分基因型株系通过寄主转移,在马尾松林生态系统中得以宿存和延续。     

江西稻瘟病菌稻巨座壳致病性分化年度动态变化

为明确江西水稻种植区稻巨座壳菌（稻瘟病病菌）的年际变化规律,本研究采用7个中国鉴别寄主与30个单基因鉴别品系两套鉴别寄主分别鉴定分析了2006-2018年间从江西37个水稻主要种植县市分离的1 161个稻瘟病单孢菌的生理小种、致病力、致病类型与无毒基因型等。研究结果表明,江西稻瘟病菌可以分成7群49个生理小种,其中ZA、ZB、ZC群为优势种群,ZB13为优势小种,出现频率为18.00%,以毒性较强的强致病力菌株为主;江西稻瘟病菌在生理小种构成、优势小种、致病力年际变化方面均具有3-5年的周期性;江西历年稻瘟病菌的致病类型较为丰富且存在年度差异,菌株致病类型占各年度总菌株数的82.79%-98.21%,优势致病型菌株占当年总菌株的3.57%-5.77%;历年稻瘟病菌的无毒基因个数为24-29个,其中Avr-Pizt、Avr-Piz5、Avr-Pik、Avr-Pik(C)在历年供试菌株中出现频率较高,说明与之相对应的抗瘟基因在江西抗病育种与抗性品种布局中具有较好的应用价值。     

陇南越夏区自生麦苗条形柄锈菌毒性表型及分子基因型分析

为了解陇南地区越夏自生麦苗上条形柄锈菌的毒性组成及群体遗传结构,将采自天水、陇南及定西的自生麦苗上的39个单孢子堆菌系采用中、美鉴别寄主毒性分析法和TP-M13-SSR荧光标记技术,进行毒性鉴定并对其基因组DNA进行SSR标记分析。结果显示：在中国鉴别寄主上供试菌系被区分为9个致病类型,在美国鉴别寄主上则得到24个毒性类型,在中美鉴别寄主上共得到30个毒性表型。通过中国鉴别寄主鉴定的CYR32、CYR33为优势小种,毒性比率分别达到35.9%和30.8%。SSR标记将这些菌系划分为36个基因型,毒性分析与     

黄瓜花叶病毒致病性研究进展

黄瓜花叶病毒(Cucumber mosaic virus,CMV)属于正义单链RNA病毒,寄主广泛,危害严重,是当前最具影响力的植物病毒之一,也是世界公认的重要植物病害。CMV自1916年报道以来,国内外学者从病毒基因、基因编码产物以及与寄主相互作用等多个方面展开了大量研究。随着高通量测序技术与蛋白质组学技术的发展,病毒相关致病机制也取得突破性进展。介绍了CMV编码蛋白,CMV相关的卫星RNA以及寄主因子在CMV侵染植物后的症状发展过程中的作用,并对今后的CMV致病性研究进行了讨论,旨为CMV的相关研究提供参考。     

基于微卫星标记的桃蚜种群寄主遗传分化

桃蚜Myzus persicae(Sulzer)是寄主范围最广、危害最大的蚜虫种类之一。为了探明桃蚜在不同寄主上的遗传分化特点,采用微卫星分子标记技术,对西兰花、桃树、辣椒上的桃蚜种群进行遗传多样性和遗传结构研究。结果表明,在所选用的5个微卫星位点上共检测到38个等位基因,平均每个位点的等位基因数达到7.6个,桃树种群遗传多样性最高,这可能是因为各种夏寄主上的桃蚜迁回桃树上越冬,从而使多种等位基因和基因型得以聚集的原因。等位基因频率差异分析显示西兰花种群、桃树种群和辣椒种群两两之间(除了桃树06种群和辣椒06种群之间没有遗传分化外)都出现了明显遗传分化,相比之下桃树种群和辣椒种群的分化程度要比桃树种群和西兰花种群的分化程度低,这可能预示着西兰花寄主上的桃蚜正在向远离桃树和辣椒种群的方向进化。     

侵染西番莲属(Passiflora)植物的五个黄瓜花叶病毒分离物的特性比较

从紫果西番莲(Passiflora edulis)、杂交种西番莲(P. edulis X P.edulis var. flavicarpa)、黄果西番莲(P.edulis var. flavicarpa)、转心莲(P.caerulea)及龙珠果(P.foetida)分离到的5个黄瓜花叶病毒(CMV)分离物(PE、PE2、PEf、PC、PF)所作的生物学性质、理化特性和血清学关系的比较研究结果表明,5个分离物在寄主反应及血清学性质上存在不同,而在病毒粒体形态、体外抗性、蚜虫传毒和病毒外壳蛋白分子量方面无明显差异.根据5个分离物的寄主反应和血清学关系,可将其区分为CMV的两个亚组,其中PE、PE2、PC和PF属CMV亚组I,PEf属CMV亚组II.     

侵染香蕉的黄瓜花叶病毒株系的血清学特征

香蕉花叶病三类不同症状,即断续条纹类（BS）、连续条纹类（CS）和斑驳类（MM）在田间广泛存在,经过血清学、生物学、核酸斑点杂交和反转录聚合酶链反应,已确定它们都由黄瓜花叶病毒（Cucumberm。。i。virus,CMV）所弓愧f’］。这三类症状分离物在鉴别寄主、粒子形态、粒子电泳相对迁移率以及在西葫芦（CI;curbitafor）和烟草（Nicotianatabacumcv．HV38）上增殖和运转动力学的特征也表现不同［’］。这些不同可能揭示了香蕉三类分离物分属不同的株系。血清学是鉴定和研究CMV株系间亲缘关系的重要依据。大量文献【’,‘1报道…     

Isolation and Characterization of Pepper Genes Interacting with the CMV-P1 Helicase Domain

Cucumber mosaic virus (CMV) is a destructive pathogen affecting Capsicum annuum (pepper) production. The pepper Cmr1 gene confers resistance to most CMV strains, but is overcome by CMV-P1 in a process dependent on the CMV-P1 RNA1 helicase domain (P1 helicase). Here, to identify host factors involved in CMV-P1 infection in pepper, a yeast two-hybrid library derived from a C. annuum ‘Bukang’ cDNA library was screened, producing a total of 76 potential clones interacting with the P1 helicase. Beta-galactosidase filter lift assay, PCR screening, and sequencing analysis narrowed the candidates to 10 genes putatively involved in virus infection. The candidate host genes were silenced in Nicotiana benthamiana plants that were then inoculated with CMV-P1 tagged with the green fluorescent protein (GFP). Plants silenced for seven of the genes showed development comparable to N. benthamiana wild type, whereas plants silenced for the other three genes showed developmental defects including stunting and severe distortion. Silencing formate dehydrogenase and calreticulin-3 precursor led to reduced virus accumulation. Formate dehydrogenase-silenced plants showed local infection in inoculated leaves, but not in upper (systemic) leaves. In the calreticulin-3 precursor-silenced plants, infection was not observed in either the inoculated or the upper leaves. Our results demonstrate that formate dehydrogenase and calreticulin-3 precursor are required for CMV-P1 infection.     

Responses of potato cultivars (Solanum tuberosum) to infection with Cucumber mosaic virus isolated from different host species

Eight isolates of Cucumber mosaic virus (CMV) isolated from seven different host species were tested for their virulence on potato cv. Desirée. Three isolates caused a systemic infection, of which one isolate from Asiatic lily (CMV-P26) and one from cucumber (CMV-J) appeared to be highly virulent, in contrast to the third isolate (CMV-M) that originated from cucumber and caused mild symptoms only. These three isolates were transmitted to 26 additional potato cultivars by mechanical inoculation in a greenhouse. All cultivars were infected with at least one CMV isolate and developed local chlorotic symptoms, but only 17 cultivars (including Desiree) developed primary systemic symptoms including necrosis, mosaic and/or malformation of leaves. Furthermore, in only five cultivars (including Desiree) CMV was transmitted to tubers and was subsequently detected in plants of the first and second vegetative progeny, the secondary symptoms of these plants being severe. The observed phenotypic responses of potatoes to CMV were not associated with the maturity type (early or late) or resistance to other viruses. Results of this study indicate a high level of biological variability among CMV isolates and that infection in potato depends on CMV isolate and potato cultivar.     

Satellite RNA for the control of plant diseases caused by cucumber mosaic virus

Two virus-protecting strains, S₅₁ and S₅₂, were obtained for the control of cucumber mosaic virus (CMV) by local lesion selection after adding satellite RNA to the RNA genome of CMV. Both were found to protect pepper plants against a virulent strain of CMV under greenhouse and field conditions. Results from 14 localities in China indicated that the use of protective strains decreased the disease index by 21.6% to 82.8% and increased fruit yields by 10.8% to 55.6%. The host reactions and safety of S₅₁ and S₅₂ were tested, and the effects of the strains on plant growth were also investigated. Possible mechanisms of control of CMV-caused plant diseases by mild strains are discussed.     

Transgenic Melon and Squash Expressing Coat Protein Genes of Aphid-borne Viruses do not Assist the Spread of an Aphid Non- transmissible Strain of Cucumber Mosaic Virus in the Field

Transgenic melon and squash containing the coat protein (CP) gene of the aphid transmissible strain WL of cucumber mosaic cucumovirus (CMV) were grown under field conditions to determine if they would assist the spread of the aphid non-transmissible strain C of CMV, possibly through heterologous encapsidation and recombination. Transgenic melon were susceptible to CMV strain C whereas transgenic squash were resistant although the latter occasionally developed chlorotic blotches on lower leaves. Transgenic squash line ZW-20, one of the parents of commercialized cultivar Freedom II, which expresses the CP genes of the aphid transmissible strains FL of zucchini yellow mosaic (ZYMV) and watermelon mosaic virus 2 (WMV 2) potyviruses was also tested. Line ZW-20 is resistant to ZYMV and WMV 2 but is susceptible to CMV. Field experiments conducted over two consecutive years showed that aphid-vectored spread of CMV strain C did not occur from any of the CMV strain C-challenge inoculated transgenic plants to any of the uninoculated CMV-susceptible non- transgenic plants. Although CMV was detected in 3% (22/764) of the uninoculated plants, several assays including ELISA, RT- PCR-RFLP, identification of CP amino acid at position 168, and aphid transmission tests demonstrated that these CMV isolates were distinct from strain C. Instead, they were non-targeted CMV isolates that came from outside the field plots. This is the first report on field experiments designed to determine the potential of transgenic plants expressing CP genes for triggering changes in virus-vector specificity. Our results indicate that transgenic plants expressing CP genes of aphid transmissible strains of CMV, ZYMV, and WMV 2 are unlikely to mediate the spread of aphid non-transmissible strains of CMV. This finding is of practical relevance because transgenic crops expressing the three CP genes are targeted for commercial release, and because CMV is economically important, has a wide host range, and is widespread worldwide.     

Detection of a single identical cytomegalovirus (CMV) strain in recently seroconverted young women

Background

Infection with multiple CMV strains is common in immunocompromised hosts, but its occurrence in normal hosts has not been well-studied.

Methods

We analyzed CMV strains longitudinally in women who acquired CMV while enrolled in a CMV glycoprotein B (gB) vaccine trial. Sequencing of four variable genes was performed in samples collected from seroconversion and up to 34 months thereafter.

Results

199 cultured isolates from 53 women and 65 original fluids from a subset of 19 women were sequenced. 51 women were infected with one strain each without evidence for genetic drift; only two women shed multiple strains. Genetic variability among strains increased with the number of sequenced genetic loci. Nevertheless, 13 of 53 women proved to be infected with an identical CMV strain based on sequencing at all four variable genes. CMV vaccine did not alter the degree of genetic diversity amongst strains.

Conclusions

Primary CMV infection in healthy women nearly always involves shedding of one strain that remains stable over time. Immunization with CMVgB-1 vaccine strain is not selective against specific strains. Although 75% of women harbored their unique strain, or a strain shared with only one other woman, 25% shared a single common strain, suggesting that this predominant strain with a particular combination of genetic loci is advantageous in this large urban area.     

Helicase Domain Encoded by Cucumber mosaic virus RNA1 Determines Systemic Infection of Cmr1 in Pepper

The Cmr1 gene in peppers confers resistance to Cucumber mosaic virus isolate-P0 (CMV-P0). Cmr1 restricts the systemic spread of CMV strain-Fny (CMV-Fny), whereas this gene cannot block the spread of CMV isolate-P1 (CMV-P1) to the upper leaves, resulting in systemic infection. To identify the virulence determinant of CMV-P1, six reassortant viruses and six chimeric viruses derived from CMV-Fny and CMV-P1 cDNA clones were used. Our results demonstrate that the C-terminus of the helicase domain encoded by CMV-P1 RNA1 determines susceptibility to systemic infection, and that the helicase domain contains six different amino acid substitutions between CMV-Fny and CMV-P1(.) To identify the key amino acids of the helicase domain determining systemic infection with CMV-P1, we then constructed amino acid substitution mutants. Of the mutants tested, amino acid residues at positions 865, 896, 957, and 980 in the 1a protein sequence of CMV-P1 affected the systemic infection. Virus localization studies with GFP-tagged CMV clones and in situ localization of virus RNA revealed that these four amino acid residues together form the movement determinant for CMV-P1 movement from the epidermal cell layer to mesophyll cell layers. Quantitative real-time PCR revealed that CMV-P1 and a chimeric virus with four amino acid residues of CMV-P1 accumulated more genomic RNA in inoculated leaves than did CMV-Fny, indicating that those four amino acids are also involved in virus replication. These results demonstrate that the C-terminal region of the helicase domain is responsible for systemic infection by controlling virus replication and cell-to-cell movement. Whereas four amino acids are responsible for acquiring virulence in CMV-Fny, six amino acid (positions at 865, 896, 901, 957, 980 and 993) substitutions in CMV-P1 were required for complete loss of virulence in 'Bukang'.     

Assessment of root-associated paenibacillus polymyxa groups on growth promotion and induced systemic resistance in pepper

Twenty-nine P. polymyxa strains isolated from rhizospheres of various crops were clustered into five genotypic groups on the basis of BOX-PCR analysis. The characteristics of several plant growth-promoting factors among the isolates revealed the distinct attributes in each allocated group. Under gnotobiotic conditions, inoculation of pepper roots with P. polymyxa isolates significantly increased the biomass in 17 of total 29 treated plants with untreated plants. Experiments on induced systemic resistance (ISR) against bacterial spot pathogen Xanthomonas axonopodis pv. vesicatoria in pepper by P. polymyxa strains were conducted and only one isolate (KNUC265) was selected. Further studies into ISR mediation by the KNUC265 strain against the soft-rot pathogen Erwinia carotovora subsp. carotovora in tobacco demonstrated that the tobacco seedlings exposed to either bacterial volatiles or diffusible metabolites exhibited a reduction in disease severity. In conclusion, ISR and plant growth promotion triggered by P. polymyxa isolates were systemically investigated on pepper for the first time. The P. polymyxa KNUC265 strain, which elicited both ISR and plant growth promotion, could be potentially used in improving the yield of pepper and possibly of other crops.     

Identification and Characterization of Tobamoviruses Strains Infecting L-resistant Genotypes of Peppers in France

Characterization of tobamovirus isolates collected from pepper crops in South East France has revealed the existance of several strains belonging to different viruses of the group. The biological and serological properties of three isolates (Vi76, Adam and Eve), selected as representative strains, have been studied. They have been compared with TMV and ToMV strains already isolated in our region as well as with other reference strains of ToMV-D and TMV-U1. They were also compared with other tobamovirus strains P11, P8 and P14, from the Netherlands, and PMMV-W from Italy also isolated from pepper genotypes possessing the “L” gene for resistance to TMV and ToMV strains. According to biological and serological reactions, Vi76 is more related to ToMV than to TMV but it is not related to Adam and Eve which are more closely related to PMMV. On the basis of the interaction with the “L” gene for resistance in pepper genotypes we have found that the Adam and P8 strains belong to the P1-2 pathotype and the Eve and P14 strains to the P1-2-3 pathotype and all the 4 strains belong to the PMMV-W group. In France, there have been no reports of the isolation of the P11 strain which is distantly related to the Adam strain.     

Differentiation of Bulgarian Isolates from Cucumber Mosaic Virus by Serological Methods

Cucumber mosaic virus (CMV) is of great importance to the Bulgarian economy and hence a detailed knowledge of its diversity under local geographic and climatic conditions is required. An extended study was carried out on CMV strains the currently occur in Bulgaria. Fifty-one isolates and strains found in different regions and various crops were biologically characterized and serologically differentiated into subgroups I and II using different variants of enzyme-linked immunosorbent assay (ELISA) [double antibody sandwich (DAS)-, antigen-coated plate (ACP)-, triple antibody sandwich (TAS)- with poly and monoclonal antibodies] and immunodiffusion tests. The ELISA modifications with monoclonal antibodies individually (ACP) or in combination with polyclonal antibodies (TAS-ELISA) are suitable for mass screening of CMV isolates. The hyperimmune sera against strains from CMV subgroups I and II were very efficient for use in isolate differentiation via gel double immunodiffusion. The results obtained correlated with the polymerase chain reaction and restriction fragment length polymorphism data reported by other authors. The majority of the isolates belonged to subgroup I, whereas 10, mainly from tomato and pepper, belonged to subgroup II. Most of the subgroup II isolates came from the north of Bulgaria. The results of the present study will help to clarify the virus epidemiology and to develop specific control measures.     

Burkholderia pseudomallei strain type, based on pulsed-field gel electrophoresis, does not determine disease presentation in melioidosis

Melioidosis, the infection due to Burkholderia pseudomallei, may present with a spectrum of severity and may affect any site in the body. Differential strain virulence and tropism suggested by previous studies would have implications for virulence and vaccine work. We explored clinical correlations using pulsed-field gel electrophoresis (PFGE) typing in a well-characterised clinical collection. Two methods of analysis were used based on band-based similarity values: first, a conventional cluster analysis formed by the unweighted paired group mean analysis, and second, an analysis of the distribution of the "within-group" and "between-group" Dice coefficient. Clinical isolates from 114 cases of melioidosis occurring in the Northern Territory, Australia were studied; 71 strain types were defined with a Simpson's index of 0.91. No correlation was found between strain type and disease severity or site of melioidosis on presentation, with no differences in similarity values found when comparing within and between-groups. In particular, isolates from patients with neurological melioidosis were not clustered. There was evidence of geographical localisation. This study suggests that the variation in strain type may not be as important as host and environmental factors in determining the pattern of disease.