河北省棉花枯萎菌遗传多样性及致病力分化

为明确河北省棉花枯萎菌（Fusarium oxysporum f.sp.vasinfectum, FOV）变异及致病力分化情况,利用AFLP技术对采自河北省的75株FOV和3号、7号、8号生理小种的标准菌株进行遗传多样性分析,并比较了不同AFLP类群菌株对棉花品种冀棉11号的致病力差异。结果表明,78株FOV可划分为4个AFLP类群（AFLP groups, AGs）,AGsⅠ为3号生理小种,AGsⅡ为8号生理小种,AGsⅢ包括7号生理小种和67株田间采集菌株,AGsⅣ包括8个田间采集菌株,该类群菌株与3号、7号、8号生理小种遗传差异较大。致病力初步测定表明,3号、7号、8号生理小种的标准菌株属中等致病力水平,而田间采集的75株枯萎菌菌株致病力存在明显差异,其中强致病力菌株占66.67%,中等致病力菌株占21.33%,弱致病力菌株占12%。表明河北省FOV群体遗传结构复杂,有遗传差异较大的新菌株出现,而且同一生理小种菌株之间存在显著的致病力分化。     

小麦秆锈菌不同小种间竞争能力的研究

本试验首次在小麦成株期把我国致病力较弱的优势小种21C3和致病力较强的低频或稀有小种34C2、34C4及116的新鲜夏孢子等量混合后,在长江流域选出的8个感病品种上继代转接。试验结果表明:温室转接5代与田间重复侵染3代后,小种21C3出现频率显著上升,小种34C2频率明显下降,小种34C4和116则下降更快,甚至完全消失。小种21C3与34C2、34C4和116相比或小种34C2与34C4和116相比,其出现频率都表现极显著差异。而小种34C4和116之间则差异不明显。说明小种21C3致病力虽不强,但竞争能力最强,故在自然界能维持优势;34C2竞争能力弱于21C3,但强于34C4和116,而且致病力较强,故在自然界也能维持一定数量。小种34C4和116致病力虽强,但竞争能力极弱,因此在自然界数量极少。     

香蕉枯萎病菌致病力分化与ISSR遗传多样性分析

香蕉枯萎病是一种破坏香蕉维管束的全株性土传病害。本研究旨在探讨香蕉枯萎病菌致病力分化和遗传多样性。以30株采自我国广西的香蕉枯萎病菌,16株分别来自澳大利亚和我国广东、海南、福建、云南等地的香蕉枯萎病菌为对象,采用伤根灌淋法测定香蕉枯萎病菌的致病力,然后用筛选到的ISSR引物对46个香蕉枯萎病菌菌株和4个对照菌株(3个非致病性尖孢镰刀菌和1个茄腐镰刀菌)进行ISSR遗传多样性分析。结果显示,分离到广西香蕉枯萎病菌1号生理小种(FOC1)8株,致病力强、中、弱类型比例分别为62.5%、12.5%和25%;广西香蕉枯萎病菌4号生理小种(FOC4)22株,致病力强、中、弱类型比例分别为18.18%、63.64%和18.18%。14条ISSR引物扩增出237个条带,多态性条带161个,多态性比例为67.93%,遗传相似系数0.76～0.96。聚类分析显示,以遗传距离0.80为阈值时菌株被分为8个类群,所占比例分别为4%、10%、60%、16%、4%、2%、2%、2%。第三类群全部为香蕉枯萎病菌4号生理小种。第一、二、四和五类群总量的70.59%为香蕉枯萎病菌1号生理小种。第八类群为香蕉枯萎病菌3号生理小种。结果表明,在香蕉枯萎病菌与寄主协同进化中,广西的FOC1和FOC4出现明显致病力分化。1号生理小种的遗传多样性比4号生理小种丰富。广西香蕉枯萎病菌4号生理小种与海南、广东的FOC4遗传相似性较高。香蕉枯萎病菌生理小种类型与遗传多样性相关。致病力变异与遗传多样性无相关性。研究结果对香蕉枯萎病菌种群扩张机制探讨、遗传动态分析以及有效防控措施的制定具有一定的指导意义。     

大蕉枯萎病病原菌鉴定及TEF-1α序列分析

 近年来,大蕉枯萎病在广东省东莞市发生严重,为了有效控制病害发生蔓延,生产上急需明确大蕉枯萎病的病原。本研究收集了我国华南地区的12株大蕉枯萎病病原菌及19株包括1号及4号生理小种的单孢菌株,以来源于澳大利亚的1号、2号、3号和亚热带4号生理小种以及4株非病原尖孢镰孢菌作对照,通过病原菌形态鉴定、致病性测定、4号小种(Foc 4)及热带4号小种(TR4)的分子特异检测、以及基于翻译延伸因子(TEF-1α)序列的系统发育分析,对大蕉枯萎病病原菌进行鉴定。同时,对我国华南地区不同来源的香蕉枯萎病病原菌的遗传发育关系及致病性分化情况进行了研究。结果表明:(1)引起大蕉枯萎病的病原菌主要是1号生理小种或者是与1号生理小种亲缘关系较近的一个新的系统发育谱系,该谱系可能为 1 号生理小种变异演化而来;(2)大蕉枯萎病病原菌对大蕉和粉蕉都有较强的致病力,但不能侵染香蕉;我国的1号小种存在一定的分化,其中有一个类群只能感染粉蕉,另一个类群既能感染粉蕉也能感染大蕉;(3)大蕉与粉蕉枯萎病的病原菌在致病性及遗传发育关系上都存在一定的交叉和分化。     

新疆棉花枯萎病菌群体结构的研究

 采自新疆24个不同植棉县(市或团场)的37株棉花枯萎病菌代表菌株,经人工接种于国际通用鉴别寄主,致病性反应均表现为典型的7号生理小种特征。RAPD分析结果也显示出这37个供试菌株与7号小种各对照菌株间基因组DNA的指纹图谱高度相似,属同一遗传相似组,而与3号和8号小种的对照菌株间遗传差异较大,亲缘关系较远,即7号生理小种是组成目前新疆棉花枯萎病菌群体的优势小种,而原分布于新疆吐鲁番等地的3号小种在本研究中未被发现。结合部分自选辅助鉴别寄主对其中18个菌株进行的致病力分化研究表明,在7号小种内部还存在着侵染力的分化,显示出棉花枯萎病菌较强的变异性和适应性。     

我国小麦条锈菌生理专化研究

根据大量的鉴定结果,进一步证明德国的小麦条锈菌鉴别寄主,除个别品种外,不能反映我国条锈菌交异的实际情况;为此,选出了比较适合我国情况的一套鉴别寄主,它们是:Trigo Eureka F.G.S.、Fulhard、Strubes Dickkopf、保加利亚春麦 Lutescens128、碧蚂1号、西北丰收、西北54号、玉皮、甘肃96号。应用所选出的鉴别寄主、四年来共分析了325个标样,它们可划分为10个不同的生理小种,定名为条中1号到10号。条中1号的出现频率最高、分布最广,它能侵染碧蚂1号、西北54号、西北丰收、农大183、石家407等品种及含有3037血统的许多品系。近年来碧蚂1号抗锈性退化即系由于该小种的猖獗。条中8号出现频率仅次于1号,它的特点是对玉皮、甘肃96号有很强致病力。条中2号出现频率虽很低,但它能侵染重要推广品种西农6028。条中3号对碧蚂1号、石家庄407、玉皮、西农6028都没有致病力,这一小种1957年出现频率很高(37.3%),但以后几年未再鉴定到;作者等推测它可能是条中1号取得优势以前的一个主要小种。已经获得的研究结果表明现阶段我国小麦抗条锈病育种工作应以条中1号、2号和8号三个小种作为主要对象。     

3种测定香蕉枯萎病病菌致病力方法的比较

由尖孢镰刀菌古巴专化型(Fusarium oxysporum fsp.cubense)引起的香蕉枯萎病严重阻碍着香蕉产业的可持续发展。为探索建立一种快捷的测定致病力的方法,以来自广东、海南的9株分离株的致病力测定为基础,8株香蕉枯萎病4号小种为研究对象,1株1号小种为对照,比较了水培苗直接浇菌法、盆栽苗伤根淋菌法、椰糠杯苗伤根浇菌法3种方法。研究发现各菌株在3种测定方法中表现的致病力强弱程度基本一致,其中以盆栽苗伤根淋菌法处理的9株病原菌间的致病力差异最大:水培苗直接浇菌法比其他2种方法操作简便且节省空间,致病周期与其他2种方法相当或更短。筛选出的水培苗直接浇菌法应更适用于分析大批量菌株间的致病力差异性,该方法操作简便,有助于病原菌致病相关基因功能分析和抗病香蕉品种选育等研究。     

高梁丝黑穗菌(Sphacelotheca reiliana (Kühn) Clint.)的生理分化

 近五年来,高粱丝黑穗菌的一个新的生理小种在辽阳、忻县发生。它侵染抗病的杂交高粱晋杂五号等。这个小种与公主岭小种的主要区别在于对3197A及甜高粱苏马克的致病力。自1970年以来,大面积栽培亲缘单一的杂交种是导致生理小种发生与变异的原因。     

粳籼89穗颈瘟分离菌株的致病力及遗传宗谱研究

通过对粳籼89的穗颈瘟分离菌株的致病力及遗传宗谱研究,结果表明:(1)粳籼89分离菌株的小种类型复杂,既有籼型小种如ZA1、ZB1、ZB5、ZB13、ZC13等,又有粳型小种如ZD5、ZG1等;(2)该类菌株的致病力存在不稳定性,同一菌株不同时间接种,鉴别寄主上表现的小种类型不同,对其他主栽水稻品种或抗源的致病力也表现不同,但这些菌株无论何时接种到粳籼89上均能使其表现感病,病级在4级以上;(3)该类菌株接种到粳籼89衍生品种或其他粳籼杂交后代上,一般能侵染这类品种;(4)利用RFLP技术,采用探针MGR586与限制性内切酶EcoRI组合对病菌进行DAN指纹分析,结果16个粳籼89分离菌株被分在2个相邻的遗传宗谱里,即宗谱1(9个菌株)和宗谱2(7个菌株),这两个宗谱恰好是广东的优势宗谱。     

农杆菌介导的西瓜枯萎病菌遗传转化

为获得带GFP标记的西瓜枯萎病菌转化株,用于后期观察病原菌侵染过程,采用农杆菌介导的方法,对西瓜枯萎病菌1号生理小种进行了遗传转化。结果表明:共培养时间为36h,枯萎病菌孢子和农杆菌AGL1比例为1∶1时该菌株的遗传转化效率最高,可以达到117.33个转化子/107个孢子。转化株的孢子、菌丝体及萌发的孢子均能发出稳定而强的绿色荧光。转化株的致病力检测显示其致病力与转化前的野生菌株致病力无明显差异。结果表明本研究获得的带GFP标记的西瓜枯萎病菌转化株可用于观察病菌在西瓜根系的侵染过程。     

Genetic diversity and pathotype determination of Colletotrichum sublineolum isolates causing anthracnose in sorghum

Amplified fragment length polymorphism (AFLP) based genetic diversity was analyzed for 232 Colletotrichum sublineolum isolates collected between 2002 and 2004 from three geographically distinct regions of Texas, and from Arkansas, Georgia, and Puerto Rico. Results revealed significant levels of polymorphism (59%) among the isolates. Even so, genetic similarity between isolates was high, ranging from 0.78 to 1.00. Clustering of similar isolates did not correlate with either geographic origin or year of collection. Pathotypes of 20 of the isolates were determined using 14 sorghum lines previously used in Brazil and the United States and 4 from Sudan. Seventeen new pathotypes were established from the 18 isolates that gave uniform and consistent reactions on all host differentials over 2?years of greenhouse testing. Differentials BTx378 and QL3 were resistant to all isolates while BTx623 and TAM428 were universally susceptible both years. Each of these lines had shown differential responses in prior studies indicating that the pathogen population has sufficient diversity to adapt rapidly to changes in resistant host lines deployed. When the 2-step pathotype classification scheme was used, the 18 isolates examined in this study were placed in four pathotype groups (A, C, D and G), which would further then be separated into ten distinct pathotypes. Common sets of differentials and a standardized nomenclature will allow for comparison to be made among pathotypes of C. sublineolum detected from different regions and also could help direct planting of appropriate sorghum lines and aid in the development of more durable forms of resistance.     

Evaluation of Ethiopian sorghum accessions for resistance against Colletotrichum sublineolum

Field experiments were conducted in the 2007 and 2008 cropping seasons in Wolayta, southern Ethiopia, to assess the reaction of 56 Ethiopian sorghum accessions and two susceptible checks (AL70 and BTx623) to anthracnose from naturally occurring inoculum. Final anthracnose severity (FAS), relative area under the disease progress curve (rAUDPC, where a commonly used susceptible cultivar, AL70, was set to 1), and anthracnose progress rate were used as evaluation parameters. All the evaluation parameters revealed significant variation among the tested accessions. In 2007, anthracnose severity varied between 6.6 and 77.7%, and in 2008 it ranged from 9.7% to 76%. The Ethiopian sorghum accessions had rAUDPC ranging from 0.13 to 0.88 in 2007 and from 0.18 to 1.35 in 2008. Anthracnose progress rate varied between 0.02 and 0.06 and from 0.01 to 0.05 units per day in 2007 and 2008, respectively. Results from the three parameters were highly correlated (0.18–0.87), suggesting FAS would be a suitable selection parameter for germplasm screening. Fifteen accessions in 2007 and 18 in 2008 were rated as resistant, with six accessions rated as resistant in both years, suggesting germplasm from Ethiopia would be useful for breeding resistance to anthracnose.     

利用抗病品种防治高粱丝黑穗病的研究

1979～1982年鉴定出19个免疫高粱品种,2个免疫恢复系,4个免疫和1个高抗不育系,其中Tx622A免疫不育系的抗病性似为显性。用Tx622A免疫不育系组配的杂交种Tx622A×4003、Tx622A×晋辐1、Tx622A×298/4003、Tx622A×锦恢75为免疫杂交种,Tx622A×208为高抗杂交种,Tx622A×白平为抗病杂交种。1981～1983年用以上抗病高产杂交种进行了20多万亩的防治示范,对丝黑穗病的防治效果均极为显著,由92～100％,平均99.0％,增产粮食1000多万斤。     

朱红毛斑蛾生物学特性研究

朱红毛斑蛾(Phauda flammans Walker)(鳞翅目:斑蛾科)是榕树上的一种重要食叶害虫,通过室内观察和野外调查,研究了朱红毛斑蛾的形态特征、年生活史及生活习性。结果表明,朱红毛斑蛾卵粒聚集排列成连续线状;幼虫共6龄;雌雄成虫可通过触角鞭节颜色、腹末有无毛须和腹部腹面体毛颜色加以区分。在广西1年发生2~3代,以第2代预蛹期幼虫及蛹和第3代低龄幼虫越冬。成虫羽化高峰为10:00-13:00;交配高峰期为13:00-18:00;产卵高峰期为11:00-15:00;幼虫仅为害榕属植物叶片,当食料缺乏时还会为害其枝条韧皮部;越冬幼虫喜欢在位于地表突出的根系附近或杂草丛下化蛹越冬,极少数在土壤表层0~10mm处做蛹室化蛹。自然条件下发现2种朱红毛斑蛾的寄生性天敌。     

Inter-isolate variation for virulence in Plasmopara halstedii (sunflower downy mildew) from Hungary

A total of 82 isolates of Plasmopara halstedii , collected from all production areas of Hungary between 1976 and 1993, were assessed for their virulence pattern on a standard set of sunflower differentials under glasshouse conditions. The isolates were classified into six pathogenic races each representing a particular virulence phenotype. From 1976 until 1988 all the isolates were found to be virulent only on sunflowers possessing no known resistance genes, thus classified as race 1. There was an apparent shift in the virulence of the P. halstedii population collected after 1988. Six races (1, 2, 3, 4, 8 and 9) were identified among the 45 samples collected between 1989 and 1993, with races 1 and 3 predominant, at a frequency of 35% each. While the increase in race virulence is undoubtedly due to selection imposed by resistant hybrids, the origin of the new races is unknown. Whether new races have arisen from the indigenous P. halstedii population, or whether they have been imported from abroad, can only be reliably determined by DNA techniques, such as fingerprinting.     

Reaction of three cotton (Gossypium hirsutum) cultivars to single and mixed isolates of Xanthomonas campestris pv. malvacearum

Cotyledons of resistant and susceptible cotton ( Gossypium hirsutum ) cultivars were inoculated artificially with four isolates of Xanthomonas campestris pv. malvacearum from Africa (H V1, HV3, H V7 and Sudan) and USA race 18. Each isolate was used as single inoculum and in combinations of mixed inoculum. Disease reactions were graded 15 days after inoculation on a scale of I (immunity) to 10 (fully susceptible). Inoculation with HVI alone produced the highest disease grade of all inoculum treatments. When HVI was included in a mixed inoculum, disease grades were greatly reduced compared to HVI alone. Disease grades were highest for the inoculum mixture of the most virulent isolates HVI and race 18, but were still reduced compared to those from HVI alone. The efficiency of selection when screening cotton germplasm for bacterial blight resistance may be reduced if the highly virulent HVI isolate is included in an inoculum mixture composed of non-virulent isolates.     

Genetics of specific resistance in pea (Pisum sativum) cultivars to seven races of Pseudomonas syringae pv. pisi

Seven races of Pseudomonas syringae pv. pisi were distinguished using eight differential cultivars of pea (Pisum sativum). Segregation among F₂ populations of crosses between differential cultivars sequentially inoculated with races of P.s. pv. pisi provided evidence for four and possibly six putative resistance(R)/avirulence(A) gene pairs. R1, R2 and R3 are dominant resistance alleles at single loci, R4 is a dominant allele at a single locus which exhibits variable expression possibly dependent on genetic background. There is evidence that R3 and R4 are at linked loci. Homology tests provided proof of the occurrence of the alleles R2, R3 and R4 in more than one cultivar. Two other alleles, R5 and R6, were postulated to explain the observed segregation ratios in certain crosses.
It can be inferred that P.s. pv. pisi races 2, 3 and 4 each carry a different single a virulence gene, race 6 carries no apparent avirulence genes, and race 7 carries at least A2, A3 and A4. Race 1 carries Al, A3, A4 and possibly A6; race 5 carries A2, A4 and possibly A5 and A6.     

Protein(s) from the Gram-Positive Bacterium Clavibacter michiganensis subsp. michiganensis Induces a Hypersensitive Response in Plants

ABSTRACT The gram-positive tomato pathogen Clavibacter michiganensis subsp. michiganensis induced a local necrotic response on four-o'clock (Mirabilis jalapa) and tobacco (Nicotiana tabacum) plants. This necrosis response was characteristic of the hypersensitive response (HR). The cell-free culture supernatant from strain CMM623 also induced a necrosis that was phenotypically similar to that induced by the bacteria. Inhibitors of plant metabolism suppressed the necrotic reaction of both M. jalapa and tobacco. The HR-inducing activity present in the supernatant was heat stable, sensitive to proteases, and had an apparent molecular mass in the range of 35 to 50 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The properties observed for the necrosis-inducing activity resembled harpin and PopA described from gram-negative phytopathogenic bacteria.     

Management of rice blast (Pyricularia oryzae): implications of alternative hosts

Rice blast (Pyricularia oryzae) has become a serious disease on commercial rice (Oryza sativa) crops in northern Australia and is present there on wild rice (O. australiensis). Characterisation of the host range of P. oryzae is fundamental to both reducing disease spread and to preventing development of epidemics via better management of Poaceae inoculum reservoirs in Australia. Studies on response of three different wild O. australiensis sources toward four isolates of P. oryzae showed all genotypes very susceptible to three isolates [WAC13466 (race IA-1), BRIP53376 (race IB-3), NT2014a (race unknown)], but resistant to isolate BRIP39772 (race IA-3). Studies to investigate levels of blast disease development following inoculation on a range of Poaceae hosts showed both P. oryzae isolates (WAC13466, BRIP53376) were highly virulent on barley (disease index, DI?=?100%), and on Phalaris and O. australiensis (DI?=?70%). However, isolate BRIP53376 showed a significantly higher level of aggressiveness (DI ~80%) on ryegrass, wild oat and rice. Of the two wheat cultivars tested, only one cultivar showed disease and only from WAC13466 (DI ~30%). Sweet corn and goosegrass were also susceptible to both blast isolates, but DI was <50%. That P. oryzae was virulent across these diverse Poaceae hosts, highlights, for Australia, the possibility for these species in, first, harbouring P. oryzae isolates highly virulent to commercial rice, second, fostering spread of rice-attacking P. oryzae strains into regions currently free of rice blast, and third, potential for these alternative host species to encourage development of more virulent host-specific strains of P. oryzae. The current study is an important step towards facilitating improved crop protection in the medium and long term from reducing P. oryzae disease epidemics via a better understanding and management of inoculum reservoirs in Australia.

     

Characterization of a resistance locus (Pfs-1) to the spinach downy mildew pathogen (Peronospora farinosa f. sp. spinaciae) and development of a molecular marker linked to Pfs-1

Downy mildew is a destructive disease of spinach worldwide. There have been 10 races described since 1824, six of which have been identified in the past 10 years. Race identification is based on qualitative disease reactions on a set of diverse host differentials which include open-pollinated cultivars, contemporary hybrid cultivars, and older hybrid cultivars that are no longer produced. The development of a set of near-isogenic open-pollinated spinach lines (NILs), having different resistance loci in a susceptible and otherwise common genetic background, would facilitate identification of races of the downy mildew pathogen, provide a tool to better understand the genetics of resistance, and expedite the development of molecular markers linked to these disease resistance loci. To achieve this objective, the spinach cv. Viroflay, susceptible to race 6 of Peronospora farinosa f. sp. spinaciae, was used as the recurrent susceptible parent in crosses with the hybrid spinach cv. Lion, resistant to race 6. Resistant F(1) progeny were subsequently backcrossed to Viroflay four times with selection for race 6 resistance each time. Analysis of the segregation data showed that resistance was controlled by a single dominant gene, and the resistance locus was designated Pfs-1. By bulk segregant analysis, an amplified fragment length polymorphism (AFLP) marker (E-ACT/M-CTG) linked to Pfs-1 was identified and used to develop a co-dominant Sequence characterized amplified region (SCAR) marker. This SCAR marker, designated Dm-1, was closely linked ( approximately 1.7 cM) to the Pfs-1 locus and could discriminate among spinach genotypes that were homozygous resistant (Pfs-1Pfs-1), heterozygous resistant (Pfs-1pfs-1), or homozygous susceptible (pfs-1pfs-1) to race 6 within the original mapping population. Evaluation of a wide range of commercial spinach lines outside of the mapping population indicated that Dm-1 could effectively identify Pfs-1 resistant genotypes; the Dm-1 marker correctly predicted the disease resistance phenotype in 120 out of 123 lines tested. In addition, the NIL containing the Pfs-1 locus (Pfs-1Pfs-1) was resistant to multiple races of the downy mildew pathogen indicating Pfs-1 locus may contain a cluster of resistance genes.