洋葱伯克氏菌群不同基因型菌株对几种重要植物病原真菌的抑制作用及其潜在致病性

从玉米和水稻根围分离到70株不同基因型的洋葱伯克氏菌,对这些菌株进行了拮抗植物病原菌的筛选,并对高拮抗菌株进行了潜在致病性和安全性分析。结果表明,有46株洋葱伯克氏菌对一种或多种病菌有较高的拮抗活性。在不同的洋葱伯克氏菌基因型内,以基因型Ⅴ内拮抗菌株占的比例最高,对所测5种病原真菌的平均拮抗菌株比率为80．0％,其中部分菌株表现出很强的拮抗活性。筛选出的4株高拮抗菌株对洋葱不具有致病性,同时也未检测到与人体致病相关的BCESM毒力基因。     

洋葱伯克氏菌作为植物病害生防菌的研究进展及其风险评价

洋葱伯克氏细菌既具有良好的生防功能但又可能是人体条件致病菌，文章就洋葱伯克氏细菌作为生防菌的研究与应用现状及存在的风险进行了综述，同时提出了其作为生防菌的应用前景与急待解决的问题。     

棉田土壤中棉花黄萎病菌的致病力分化

为了明确同一棉田生态系中棉花黄萎病菌的群体组成和致病力分化特点,利用病害反应型及病情指数测定法,对来自同一棉田的43个棉花黄萎病分离菌株在5个鉴别寄主上进行了致病力测定。结果表明,43个菌株可划分为落叶型致病力强的Ⅰ型、混合型致病力中等的Ⅱ型和非落叶型致病力弱的Ⅲ型。其中Ⅰ型菌株19个,占44.2%,平均病情指数大于50;Ⅱ型菌株16个,占37.2%,平均病情指数在30～50之间;Ⅲ型菌株8个,占18.6%,平均病情指数小于30。由此证明,同一棉田棉花黄萎病存在落叶型和非落叶型两类病害表现类型,其病原菌存在强、中、弱三种不同致病类型的生理型,揭示出棉花黄萎病菌本身是一个易变异的混合基因型群体,群体中的不同个体组成的亚群体具有不同的致病性。     

青枯雷尔氏菌Ⅲ型分泌系统hrcN基因的功能分析

hrcN是植物病原菌Ⅲ型分泌系统基因（T3SS）的结构基因之一,对病原菌的致病力有重要影响。本研究克隆青枯雷尔氏菌CBM613的hrcN基因并作生物信息学分析,结果显示该基因长度为1320 bp,共编码439个氨基酸,预测HrcN蛋白无信号肽,无跨膜区域,整体呈弱亲水性,该蛋白为ATP酶,定位于细胞内膜和细胞质。基因敲除结果显示,菌株CBM613的hrcN突变体与野生型菌株在富营养培养基上的生长速率差异不明显,而在贫营养培养基上前者的生长速率显著快于后者。敲除hrcN基因后,青枯雷尔氏菌的运动能力无明显变化,生物被膜形成能力显著降低。以敲除突变型和野生型青枯雷尔氏菌株接种番茄,与后者相比,前者的致病力下降,病情指数降低,病程延长,但并未完全丧失致病力,表明hrcN基因是青枯雷尔氏菌致病性相关的重要基因。本研究为进一步探索青枯雷尔氏菌致病机制及防治具有重要意义。     

广东水稻白叶枯病菌新致病型的发现及致病性测定

在对广东省水稻白叶枯病菌的致病型变异动态监测中,发现了在中国鉴别寄主金刚30、Tetep、南粳15、Java14、IR26上的反应为SSSSS模式的菌株。该菌株有别于SRRRR(Ⅰ型)、SSRRR(Ⅱ型)、SSSRR(Ⅲ型)、SSSSR(Ⅳ型)、SSRRS(Ⅴ型)、SRSRR(Ⅵ型)、SRSSR(Ⅶ型)、RRRSR(云南菌型)8个类型,是1个新致病型菌系。对该菌系致病性测定的结果显示,其致病谱广、毒性强,是1个高致病性菌系。广东水稻白叶枯病菌新致病型的发现及致病性测定@曾列先$广东省农科院植物保护研究所!广东广州510640…     

柑桔溃疡病内生拮抗细菌Bc51的研究

 从中国南宁柑桔叶片中分离到对柑桔溃疡病菌有拮抗作用的细菌菌株Bc51。根据16S rDNA序列同源性、形态学特征和生理生化反应,将该菌株鉴定为洋葱伯克霍尔德氏菌(Burkholderia cepacia)。温度、pH值和培养基对洋葱伯克霍尔德氏菌抑制柑桔溃疡病菌生长的能力有显著影响。在温室测试中,观察到60.3%柑桔溃疡病斑的形成受到洋葱伯克霍尔德氏菌抑制。连续8次在人工培养基上转代培养,洋葱伯克霍尔德氏菌对柑桔溃疡病菌生长的抑制力没有发生明显改变。洋葱伯克霍尔德氏菌对植物病原菌有较宽的抑菌谱,表明除柑桔溃疡病外,该菌对其它作物病害的防治也具有潜在的应用价值。     

江苏省大丽轮枝菌的培养、遗传及致病特性分析

由大丽轮枝菌引起的黄萎病是我国棉花和茄子的主要病害之一,对棉花和茄子的生产造成巨大损失。为了研究大丽轮枝菌的群体遗传变异以及对棉花和茄子的交互致病性,本文对分离自江苏省的63个棉花黄萎菌和10个茄子黄萎菌进行了培养、遗传和致病特性分析。根据菌株在PDA培养基上生长时形成微菌核的多少来划分培养类型,结果菌核型占83.6%,成为主要的培养类型。用PCR技术检测菌株的致病类型、交配型以及是否具有无毒基因Ave1,结果落叶型菌株占86.3%,为优势种群,但是10株茄子黄萎菌100%都是非落叶型菌株;供试的所有江苏菌株交配型都是MAT1-2型,并且都没有无毒基因Ave1。选择江苏省的6个棉花黄萎菌和4个茄子黄萎菌在室内苗期接种棉花和茄子,进行交互致病性测定,结果这10个菌株都可以侵染棉花和茄子,而且来源于不同寄主作物的菌系之间致病力分化明显,表现在不同菌株对同一寄主的致病力不同,同一菌株对不同寄主的致病力也不同。研究结果为深入研究大丽轮枝菌群体遗传结构和制定黄萎病防治措施提供了理论支持。     

洋葱腐烂病菌PCR检测方法的建立

为了快速准确检测洋葱腐烂病菌（Burkholderia gladioli pv. alliicola，简称Bga），根据GenBank中Bga与相关种的序列差异设计特异引物BG5/BG7和探针Bga-P，建立了Bga常规PCR和荧光PCR检测方法。测试结果表明，引物和探针对供试的11株Bga菌株表现为阳性反应，其他64株供试菌株和空白对照均为阴性。常规PCR和荧光PCR方法的检测灵敏度分别为24 pg和240 fg菌体DNA。美国、法国、意大利等国进境的80批次洋葱种子样品的检测结果显示，这两种方法的阳性检出率分别为7.5%和12.5%。选取阳性样品进行病菌分离，成功从2批次法国进境洋葱种子中分离到目的菌。本文建立的洋葱腐烂病菌PCR检测方法可为口岸检测部门提供更高效、灵敏和特异的检测手段。     

洋葱伯克霍尔德氏菌株Lyc2的鉴定及对棉苗的防病促生作用

 从烟草根际土壤中分离到一株细菌菌株Lyc2,平皿对峙培养显示该菌可显著抑制多种植物病原真菌菌丝体的生长。温室盆栽试验表明,Lyc2对棉花苗期立枯病的防治效果达到48.8%;水培棉花苗试验表明,Lyc2能显著增加棉苗的鲜重和干重,但对株高的影响不显著。该菌经形态、生理生化试验测定及16S rDNA和ITS序列分析,初步确定为洋葱伯克霍尔德氏菌(Burkholderia cepacia);进一步通过种特异的recA基因序列分析,证明Lyc2菌株属于B. cepacia复合物中基因型IX,B.pyrrocinia。     

青枯菌Po82菌株Ⅲ型分泌系统调控基因hrpB的功能研究

本文以青枯菌致病力分化菌株Po82的Ⅲ型分泌系统调控基因hrpB为研究对象,采用同源重组双交换法,构建获得青枯菌Po82菌株的hrpB基因缺失突变株Po82ΔhrpB及其互补菌株Po82ΔhrpB-pML123-hrpB,并对野生型菌株、突变株和互补菌株进行了致病力及生物学功能的验证。致病力测定结果表明,青枯菌hrpB基因缺失突变株Po82ΔhrpB的致病力较Po82野生型菌株显著下降,而互补菌株Po82ΔhrpB-pML123-hrpB能够部分恢复突变菌株的致病力。生长曲线测定结果表明,在营养贫瘠型培养基中,hrpB基因缺失突变株Po82ΔhrpB的生长速率较野生型青枯菌Po82菌株快,但是在营养丰富型培养基中,两者生长速率基本一致。野生型和突变株的运动性测定结果显示,两者的运动性无显著差异。表明hrpB基因在青枯菌致病过程中具有重要影响,并对进一步发掘鉴定Po82菌株中新的Ⅲ型效应子,进而深入解析其致病力分化的分子机理具有重要的作用。     

山东棉花黄萎菌致病力分化的研究

选用山东省有代表性的棉黄萎菌１６个菌株（系）各配制成一定浓度的孢子悬浮液，于棉苗２～３叶期蘸根接种，观察发病的反应型。结果表明：各菌株致病力强弱差异明显，可分为致病力强的Ⅰ型（即与落叶型相似）、致病力中等的Ⅱ型和致病力弱的Ⅲ型，并发现山东省有落叶型菌系存在。     

Molecular Typing and Presence of Genetic Markers Among Strains of Banana Finger-Tip Rot Pathogen, Burkholderia cenocepacia, in Taiwan

ABSTRACT Burkholderia cenocepacia (genomovar III of B. cepacia complex), the causal agent of banana finger-tip rot, is a common plant-associated bacterium but also an important opportunistic pathogen of humans. To better understand the nature of B. cenocepacia from banana, the genetic variation among B. cenocepacia isolates from various banana-growing regions in southern Taiwan was examined. Forty-four serial isolates recovered from diseased banana stigmata from three banana-growing regions during the periods ranging from 2002 to 2004 were investigated. All B. cenocepacia isolates picked from quinate-yeast extract tetracycline-polymyxin semiselective medium could cause onion maceration and were polymerase chain reaction (PCR) positive for bcscV, which is a type III secretion gene present in all members of the B. cepacia complex except B. cepacia (formerly genomovar I). Genetic diversity was assessed using recA PCR restriction fragment length polymorphism, recA nucleotide sequence analysis, and pulsed-field gel electrophoresis assays. The assays revealed the genetic variability among the isolates and also allowed us to trace the relationship among isolates. The isolates all were assigned to genomovar III and consisted of two groups, A and B, which corresponded to recA lineage IIIA and IIIB. The group B strains were separated into B1 and B2 subgroups and the B1 strains were further divided into distinct lineages. The B1 strains were the most frequently detected and occurred in all regions tested. There was no significant difference between strains from each subgroup in the virulence on banana fingers of cv. Cavendish. PCR assays were further used to determine whether B. cenocepacia from banana contained the cable pilus subunit gene (cblA), IS1356, and B. cepacia epidemic strain marker (BCESM), which are DNA markers associated with epidemic B. cepacia clinic strains. The results indicated that cblA and IS1356 were absent but the BCESM was found in all isolates. The present study revealed that banana is a natural reservoir of genetically diversified B. cenocepacia strains.     

Polyphasic characterization of xanthomonas strains from onion

ABSTRACT Xanthomonas leaf blight has become an increasingly important disease of onion, but the diversity among Xanthomonas strains isolated from onion is unknown, as is their relationship to other species and pathovars of Xanthomonas. Forty-nine Xanthomonas strains isolated from onion over 27 years from 10 diverse geographic regions were characterized by pathogenicity to onion and dry bean, fatty acid profiles, substrate utilization patterns (Biolog), bactericide resistance, repetitive sequence-based polymerase chain reaction fingerprinting, rDNA internally transcribed spacer (ITS) region, and hrp b6 gene sequencing. Multiplication of onion Xanthomonas strain R-O177 was not different from X. axonopodis pv. phaseoli in dry bean, but typical common bacterial blight disease symptoms were absent in dry bean. Populations from each geographical region were uniformly sensitive to 100 mug of CuSO(4), 100 mug of ZnSO(4), and 100 mug of streptomycin sulfate per ml. Biolog substrate utilization and fatty acid profiles revealed close phenoltypic relatedness between onion strains of Xanthomonas and X. axonopodis pv. dieffenbachiae (57% of strains) and X. arboricola pv. poinsettiicola (37% of strains), respectively. A logistic regression model based on fatty acid composition and substrate utilization classified 69% of strains into their geographical region of origin. Sequencing of a portion of the hrp B6 gene from 24 strains and ITS region from 25 strains revealed greater than 97% sequence similarity among strains. DNA fingerprinting revealed five genotype groups within onion strains of Xanthomonas and a high degree of genetic diversity among geographical regions of origin. Based on pathogenicity to onion, carbon substrate utilization, fatty acid profiles, rDNA genetic diversity, and genomic fingerprints, we conclude that the strains examined in this study are pathovar X. axonopodis pv. allii. Implications of genetic and phenotypic diversity within X. axonopodis pv. allii are discussed in relation to an integrated pest management program.     

Pathogenicity and molecular phylogenetic analysis reveal a distinct position of the banana fingertip rot pathogen among the Burkholderia cenocepacia genomovars

Banana (Musa spp.) is one of the most widely cultivated subtropical fruits around the globe. Banana cultivation has been extensively increased in southeastern Iran over the last two decades. Recently, banana fruits possessing rotten and blackened fingertip symptoms were observed in Sistan-Baluchestan, Iran. Isolation and characterization of the causal agent showed that the pathogen belongs to the multifaceted bacterial species Burkholderia cenocepacia. Pathogenicity tests and host range assays showed that the strains were pathogenic on banana, as well as carrot, onion and potato. All the strains were resistant to 50 mg L⁻¹ rifampicin and 200 mg L⁻¹ copper sulphate. Phylogenetic analysis of 16S rRNA and recA gene sequences showed that the strains belong to two different genomovars of B. cenocepacia (III-A and III-B), which also include environmental and cystic fibrosis associated strains of the species. The results obtained from recA phylogeny were confirmed using multilocus sequence analysis (MLSA), although MLSA showed that the banana strains were clustered as a novel phylogroup among the members of both genomovars. Banana-pathogenic B. cenocepacia strains isolated in Iran were different from the strains isolated in Taiwan, as the ‘B. cepacia epidemic strain marker’ reported in the Taiwanese strains was absent from Iranian strains. To the authors’ knowledge, this is the first MLSA-based study on the banana-pathogenic strains of B. cenocepacia. However, further in-depth molecular studies are needed to decipher the relationships between the banana fingertip rot pathogen and the clinical strains of B. cenocepacia.     

Occurrence of bacterial rot of onion bulbs caused by Burkholderia cepacia in Japan

In 2001, a bacterial rot of onion (Allium cepa L.) bulbs was observed in Japan. The causal agent was identified as Bukholderia cepacia (Palleroni & Holmes 1981 ex Burhkolder 1950) Yabuuchi, Kosako, Oyaizu, Yano, Hotta, Ezaki, and Arakawa 1993. The identified bacteria were divided into two groups (Y and W) based on colony colors, and several phenotypic and genetic characteristics. Based on recA polymerase chain reaction assays, the strains of the Y and W groups belong to genomovar I (B. cepacia sensu stricto) and genomovar III (B. cenocepacia), respectively.The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession numbers AB162427 and AB162428     

棉花枯萎镰刀菌致病力变异的研究Ⅱ.生理Ⅱ、Ⅲ型菌系异核现象的研究

 本研究是对棉花枯萎镰刀菌生理Ⅱ、Ⅲ型菌系的四个菌株用切割菌丝尖端和单孢分离的方法研究它们的异核现象。试验结果表明:在田间它们能以异核体存在,并有三种核型组成,通过对Ⅲ型菌系的野生异核体菌株及原生质融合异核体菌株进行致病力测定,致病力发生了变异,证明异核现象是Ⅲ型菌系致病力变异的重要因素之一。     

<Emphasis Type="Italic">Pantoea ananatis</Emphasis> strains are differentiated into three groups based on reactions of tobacco and welsh onion and on genetic characteristics

Ninety-six strains of Pantoea ananatis were isolated from 14 plant species including melon, rice, tea and other crops of economic importance. They were classified into three groups (group I, II, III) based on a welsh onion stabbing assay, tobacco infiltration test, and polymerase chain reaction to detect indole acetic acid (IAA) biosynthesis genes (iaaM and iaaH) and a cytokinin biosynthesis gene (etz). Group Ι strains were characterized as causing significant blight symptom on welsh onion and inducing a hypersensitive response (HR)-like reaction on tobacco leaves after 36–48 h and encompassed 20 isolates from foxtail millet, hydrangea, pineapple, river water and rice. These 20 isolates did not possess iaaM, iaaH, or etz genes. Group II, consisting of 34 melon isolates, harbored iaaM, iaaH and etz genes, but did not cause either blight on welsh onion or HR-like reaction on tobacco. Group III strains did not have the iaaM, iaaH, and etz genes, nor did they cause any reaction on welsh onion or tobacco. The 42 strains in group III were isolated from bamboo grass, Chinese silver grass, citrus, dogwood, melon, mugwort, silk tree, sweet corn, tea and welsh onion. Representative strains of the three groups were tested for pathogenicity on melon and rice. Group Ι strains caused palea browning on rice but not internal fruit rot on melon. On the contrary, group II strains did not cause disease on rice but caused internal fruit rot on melon. Group III strains were not pathogenic on rice or melon. These results suggested that the host range of P. ananatis may be predicted by the reactions of welsh onion and tobacco and detection of iaaM, iaaH and etz genes. These tools may serve as rapid tests to identify the pathogenicity groups of P. ananatis.     

罗汉果青枯病病原菌株的鉴定

 The pathogen of Siraitia grosvenorii wilt was identified.Six strains were isolated from diseased plants of S.grosvenorii collected from Yongfu County in Guangxi.By using bacteriological identification,pathogenicity tests assay,16S rDNA sequence analysis,the S.grosvenorii wilt was caused by Ralstonia solanacearum.The results of pathogenicity and carbohydrate utilized test demonstrated that the pathogen belonged to race 1 and biovarⅢ of R.solanacearum.     

农户型“猪-沼-石榴”循环农业模式能值及经济效益

以农户型"猪-沼-石榴"循环农业模式(模式Ⅰ)作为切入点,将单一石榴种植模式(模式Ⅱ)和单一生猪养殖(模式Ⅲ)作为参考,运用能值理论和方法对三种模式的结构、能值流特征、综合效益进行定量分析。结果表明:三种模式中,模式Ⅰ能值产投比(OIR)8.49,高于模式Ⅲ,低于模式Ⅱ;能值反馈率(EFR)最低0.010;环境负载率(ELR)最低,分别降低了1.647、0.530;能值废弃率(EWR)最低,降低了14.4%;系统可持续发展性能(EISD)最高,分别增加了9.823、8.830;对比单一农业模式,模式Ⅰ各子系统经济产投比在不同程度上都有所增加。综上说明该模式具有资源利用率高、低排放、环境压力小、富有活力和可持续发展潜力,生态经济综合效益佳等优势,可将农村地区生活方式由资源浪费型转变为清洁节约型。