Characterization of fungi (Fusarium and Rhizoctonia) and oomycetes (Phytophthora and Pythium) associated with apple orchards in South Africa

Several species of fungi and oomycetes including Fusarium, Rhizoctonia, Phytophthora and Pythium have been reported as root pathogens of apple where they contribute to a phenomenon known as apple replant disease. In South Africa, little is known about specific species in these genera and their pathogenicity toward apple. Therefore, these aspects were investigated along with the development and optimization of qPCR tests for detection and quantification of the most virulent oomycete species. In eight investigated orchards, the oomycete Phythophthora cactorum was widely distributed, while nine Pythium species were differentially distributed among the orchards. Pythium irregulare was the most widely distributed and the most virulent species along with P. sylvaticum, P. vexans and Ph. cactorum. Seven binucleate Rhizoctonia anastomosis groups (AGs) were also differentially distributed among the orchards, with the majority appearing to be non-pathogenic while certain AG-I and AG-F isolates exhibited low virulence on apple. In the genus Fusarium, F. oxysporum was widely distributed, but isolates were non-pathogenic. Fusarium solani and F. avenaceum were less frequently encountered, with only some isolates having low virulence. qPCR data obtained from seedling roots inoculated with the most virulent Pythium species (P. irregulare, P. sylvaticum and P. vexans) and the genus Phytophthora were not always reproducible between trials, or isolates of the same species. In general, seedling growth inhibition was associated with the presence of a low amount of pathogen DNA (±40 fg μl⁻¹ to 2 pg μl⁻¹) in roots. Pythium irregulare, although having the lowest DNA concentrations in roots, was the only species for which a significant negative correlation was found between seedling weight and pathogen DNA concentration.     

Characterisation of a proposed Nucleorhabdovirus new to South Africa

A previously uncharacterised plant rhabdovirus, infecting Bermuda grass (Cynodon dactylon) in the North West Province, South Africa, has been found. To determine the morphology and virion size of this virus, embedded ultra-thin sections of infected plant samples were observed under a transmission electron microscope. The virion distribution within the cell, its bullet-shaped morphology and its size (240 × 63 nm) indicated that this might be a rhabdovirus of the genus Nucleorhabdovirus. Degenerate polymerase chain reaction (PCR) primers were designed by alignment of the polymerase gene sequences of several plant rhabdoviruses in order to identify conserved regions. Standard PCR and sequencing protocols were used to determine a partial polymerase gene sequence of this virus sample which was then compared to the most closely related sequences available on Genbank. The analysis indicated that the virus was indeed most closely related to known nucleorhabdoviruses, with the highest nucleotide sequence similarities being to Maize mosaic virus and Taro vein chlorosis virus (70% and 69.7% respectively). Serological testing indicated that the South African Cynodon rhabdovirus had a close serological relationship with the nucleorhabdovirus Cynodon chlorotic streak virus.     

草莓腐霉根腐病病原菌鉴定

<正>近年来草莓栽培面积不断扩大,其病害也逐渐增多,尤其是叶部病害和根腐病逐年加重,成为该产业发展的主要障碍之一。草莓腐霉根腐病主要危害根部和茎基部,造成死棵现象,发病速度快,随着浇水短时间内可造成整行死亡,严重时整个草莓大棚被毁灭。病原菌鉴定是病害有效防控的基础,但目前尚未见关于草莓腐霉根腐病病原     

检疫性疫霉DNA条形码筛选

 疫霉是世界关注的一类植物病原真菌。以疫霉属80个种122个菌株为研究材料,以ITS、CO1、EF-1α和β-tubulin 4个基因片段为候选DNA条形码,分析表明ITS、CO1基因的PCR扩增和测序成功率最高,分别为100%和96.7%;ITS、CO1和β-tubulin存在明显的条码间隔,但种间、种内距离频率分布存在较小重叠;种间、种内遗传距离Wilcoxon秩和检验结果认为各基因对种内遗传距离的效力相等,对种间遗传距离的区分能力为ITS>CO1>β-tubulin。CO1基因和ITS片段可同时作为11种检疫性疫霉的首选DNA条形码,β-tubulin基因可作为辅助DNA条形码。     

利用环介导等温扩增(LAMP)技术快速检测辣椒疫霉菌

<正>辣椒疫霉(Phytophthora capsici)是一种重要植物病原菌,能造成植株坏死、果实腐烂,严重影响产量[1]。辣椒疫霉侵染植物的早期病症并不明显,易被忽视。因此,对辣椒疫霉早期快速、准确检测显得尤为重要。聚合酶链式反应(PCR)为动植物病原物检测的重要方法,但需要较昂贵的仪器、试剂与耗材,后期的电泳检测也费时费力,致使这一技术很难在生产一线普及推广。Notomi等2000年研发了环介     

辣椒疫霉致病力分化的初步研究

关于辣椒疫霉Phytophthora capsici Leonian致病力的分化研究,Black等曾报道来自台湾的辣椒疫霉对辣椒有一定的寄生专化性,菌株间存在致病力分化现象,可分为3种致病型,国内这方面的研究迄今报道较少。为了明确安徽省辣椒疫霉是否存在致病力分化现象,为辣椒抗病育种及该病的防治提供理论依据,作者对分离自该省不同地区的辣椒疫霉菌株的致病力及其分化进行了初步研究,结果如下。     

柑橘叶点霉属(Phyllosticta spp.)真菌的遗传多样性分析

利用筛选的11条ISSR引物对从我国柑橘主产区和国外收集的135株叶点霉属真菌菌株进行扩增,扩增产物进行凝胶电泳,扩增图谱用NTSYS-pc2.10软件进行群体聚类分析。结果显示,共扩增出116个DNA条带,其中多态性位点为112个,多态率为96.55%;平均每个引物可以扩增出10.55个条带,扩增产物大小在250~3 000 bp。聚类分析显示,中国柑橘叶点霉属真菌可以分为4个种,即P.citricarpa、P.citriasiana、P.capitalensis和P.citrichinaensis。以遗传相似性系数0.97为阈值时,柑橘黑斑病病原菌(P.citricarpa)种群可分为5个亚类,subclade-I的菌株来自中国的本地早、温州蜜柑、槾橘和南丰蜜橘,subclade-II的菌株均来自中国的砂糖橘,subclade-III的菌株来自非洲莫桑比克柠檬和葡萄柚、佛罗里达甜橙、南非甜橙和来自杭州市场上进口的澳橘,subclade-IV的菌株来自中国的甜橙,subclade-V的菌株来自中国的柠檬,表明我国柑橘黑斑病病原菌具有丰富的遗传变异,其遗传变异与寄主相关;我国与国外的柑橘黑斑病病原菌在起源上可能存在差异。P.citriasiana、P.capitalensis和P.citrichinaensis种群内也存在遗传变异,但其遗传变异与地理分布和寄主未发现相关性。该研究结果为研究柑橘叶点霉属真菌的遗传多样性奠定了基础。     

云南魔芋新病害—疫病病原菌的鉴定

<正>魔芋为天南星科(Araceae)魔芋属(Amorphophallus Blume)植物,是富含葡甘露聚糖的经济作物。随着人们对魔芋葡甘露聚糖的进一步研究和深度开发利用,魔芋的生产越来越受到重视,种植方式也由传统的半野生零星种植转向规模化大面积种植。云南是魔芋的起源中心之一[1],其气候环境非常适宜魔芋的生长和种植,但由于规模化种植程度的扩大以及芋农较为粗放的栽培管理方式,魔芋病害日趋严重,新病害亦不断出现。20世纪90年代初,我国魔芋有3种主要病害,现已增至11种。最近在云南省魔芋不同生育期的叶片及茎杆上又发现一种新病害——魔芋疫病。该病水渍状的黑     

Characterisation of pectobacterium wasabiae causing blackleg and soft rot diseases in South Africa

Pectolytic bacteria were isolated from potato tubers and stems showing tuber soft rot and blackleg symptoms. Approximately half (52 %) of the isolates could grow at both 27 and 37 °C while another half (48 %) failed to grow at 37 °C. All isolates could be amplified with primers specific to the pectate lyase (pel) gene. Carbon utilisation profiles could not conclusively identify these isolates. PCR amplification using primers specific for Pectobacterium carotovorum subsp. brasiliensis was positive for all isolates that grew at 37 °C. However, the group that did not grow at 37 °C failed to amplify with P. atrosepticum specific primers. To characterise this group of isolates, the intergenic transcribed spacer region (ITS) was amplified and PCR products digested with two restriction enzymes (RsaI and CfoI) to generate ITS-PCR-RFLP profiles. The profiles of these new isolates were compared to those of the type strains of other pectolytic bacteria. Profiles of five of the selected atypical strains generated with the enzyme CfoI appeared to be most similar to those of P. wasabiae type strain. Phylogenetic analysis using concatenated partial gene sequences of housekeeping genes mdh and gapA clustered these isolates together with those of P. wasabiae reference strains thus confirming their identity. These strains were virulent on potato tubers and stems but did not elicit hypersensitive response on tobacco plants. This is the first report of P. wasabiae causing soft rot and blackleg of potatoes in South Africa.     

寡雄腐霉GAQ1对辣椒疫病的防效及对辣椒的促生作用

为明确自主分离的生防菌株寡雄腐霉Pythium oligandrum GAQ1对辣椒疫病的生防效果及其防御机制,通过平板拮抗和盆栽防效试验测定寡雄腐霉菌株GAQ1对辣椒疫霉Phytophthora capsici菌丝的拮抗作用、对辣椒疫病的防效和对辣椒的促生效果,同时应用实时荧光定量PCR技术检测菌株GAQ1处理后辣椒抗性基因表达的变化。结果表明,寡雄腐霉菌株GAQ1的菌丝可以缠绕并吸附寄生在辣椒疫霉菌丝表面或穿入菌丝体内,使辣椒疫霉菌丝细胞死亡;菌株GAQ1发酵液处理辣椒离体叶片再接种辣椒疫霉后产生的病斑直径较对照组显著减少,离体防效为30.79%;接种菌株GAQ1菌丝球后,辣椒疫病的病情指数较对照组显著降低,盆栽防效达69.16%;经菌株GAQ1处理辣椒后可诱导相关抗性基因PR1、WRKY40、WRKY53、ACCO和GST的相对表达量出现不同程度的升高,说明菌株GAQ1可诱导辣椒植株产生不同程度的防御系统应答。菌株GAQ1对辣椒具有良好的促生效果,处理后第5周其株高、株重及根重分别较对照组提高10.11%、33.23%和24.72%,其叶片中叶绿素a、叶绿素b及类胡萝卜素的含量分...     

引起我国甜樱桃叶斑病的间座壳菌种类鉴定

为明确引起我国甜樱桃叶斑病的病原菌种类,于2019年在北京市、四川省、山东省和辽宁省对与已报道的其他叶斑病症状明显不同的一种甜樱桃叶斑病进行调查并采集病叶,通过组织分离法进行病原菌分离纯化,结合形态学特征和多基因(ITS、EF1-α、TUB2和CAL)系统发育分析对病原菌的种类进行鉴定,并采用离体叶片接种法进行致病性测定。结果显示,新发现的这种甜樱桃叶斑病通常从叶边缘产生圆形或不规则灰褐色病斑,病斑周围具黄色晕圈,有时形成穿孔。从病样中共分离纯化得到10株单孢系菌株,结合其菌落形态、分生孢子形态和大小等,以及多基因系统发育分析结果,最终将10株菌株鉴定为甜樱间座壳Diaporthe eres(5株)和大豆间座壳D. sojae(5株),致病性测定结果显示甜樱间座壳和大豆间座壳对甜樱桃叶片均具有致病性,完成柯赫氏法则验证。     

安徽省大豆疫霉根腐病菌的鉴定及rDNA-ITS序列分析

为明确安徽省夏大豆疫霉根腐病的病原菌种类,对采集自涡阳、怀远、固镇3个县的夏大豆病株及土样分离纯化后获得28株菌株,选取6株代表性菌株,通过形态学观察及核糖体DNA-ITS序列分析对其进行鉴定,并测定了其致病型。结果表明,6株菌株在利马豆培养基上菌落白色,质地均匀;菌丝无隔,致密,具近直角分枝;在10%V8C培养液中,游动孢子囊顶生,不脱落,卵形至椭圆形,无明显乳突,有内层出现象,长宽比大于1.6∶1;同宗配合,在利马豆培养基上单株培养产生大量卵孢子,藏卵器球形,雄器大多侧生;接种合丰35大豆品种后出现典型的大豆疫霉根腐病症状。r DNA-ITS序列分析表明,6株菌株与Gen Bank中大豆疫霉Phytophthora sojae的ITS序列同源性高达100%;菌株GY4、GY8、HY11、HY16、GZ10、GZ21的毒力公式分别为1b,2,3a,3b,4,5,6,7;1b,1d,3a,3b;1d,3a,3b,3c,4,5,6,7;2,3c,4,5,6,7;1b,3a,3c,5,8;3a,3b,5,6,7,8;属于6个不同的致病型。研究表明,这6株菌株均为大豆疫霉。     

引起青海省马铃薯根腐类病害的镰刀菌种类鉴定

<正>马铃薯是继水稻、小麦和玉米之后的第四大粮食作物~([1]),也是我国青海省主要的经济作物。马铃薯干腐病是镰刀菌根腐类病害中最重要的一种病害,其窖藏期发病率最高可达60%~([2]),根腐类病害已成为限制青海省马铃薯产业发展的重要因素。本文通过形态学、EF-1α基因序列分析的分子生物学鉴定及致病性测定,明确了引起青海省马铃薯根腐类     

甘肃省玉米籽粒中镰孢菌分离频率及伏马毒素含量监测

为了解甘肃省玉米籽粒中病原镰孢菌的种类以及籽粒中伏马毒素的含量,通过形态学特征、分子生物学鉴定和高效液相色谱法对2011—2012年间采自甘肃省5个地区的225份玉米籽粒样品进行了镰孢菌的分离、鉴定和伏马毒素含量的测定。结果表明,分离获得的516株镰孢菌经鉴定分别属于拟轮生镰孢菌Fusarium verticillioides、层出镰孢菌F.proliferatum、禾谷镰孢复合种F.graminearum species complex、亚粘团镰孢菌F.subglutinans、藤仓镰孢菌F.fujikuroi、木贼镰孢菌F.equiseti、尖镰孢菌F.oxysporum和F.temperatum;其中拟轮生镰孢菌分离频率最高,属甘肃省的优势病原菌。2011和2012年,镰孢菌的分离频率分别为31.0%和10.7%,禾谷镰孢复合种和拟轮生镰孢菌为当年的优势种群。同时,2011和2012年样品中伏马毒素的污染率分别为30.5%和50.9%,平均含量分别为175μg/kg和224μg/kg,但未发现伏马毒素含量超过欧盟委员会限量标准(4 000μg/kg)的样品。     

Pectinolytic bacteria associated with potato soft rot and blackleg in South Africa and Zimbabwe

Soft rot and blackleg can cause severe economic losses in potato production in South Africa and Zimbabwe depending on climatic conditions. The aim of the study was to identify the predominant bacteria causing potato soft rot and blackleg in these countries. Samples, comprising of stems and tubers from potato plants with blackleg and soft rot symptoms were collected from 2006?C2009 from potato production areas where disease outbreaks occurred. The isolates from these plants and tubers yielded Gram negative, pectinolytic bacteria on crystal violet pectate and inoculated tubers. Identification was based on biochemical and phenotypic characteristics, rep-PCR, Amplified Fragment Length Polymorphisms and sequences of gyrB and recA genes. Isolates from Zimbabwe were identified as Pectobacterium carotovorum subsp. brasiliensis (Pcb) (21 isolates), Dickeya dadantii subsp. dadantii (Dd) (20 isolates), P. c. subsp. carotovorum (Pcc) (16 isolates) and P. atrosepticum (Pa) (4 isolates). Pcb, Pcc and Dd subsp. dadantii were isolated from samples collected from all the regions, while Pa was isolated from Nyanga the coolest region in Zimbabwe. In South Africa, however, Pcb was the most common causal agent of soft rot and blackleg. P. atrosepticum was the only pathogen isolated from samples collected in Nyanga, Zimbabwe, and was not isolated from any South African samples. AFLP analysis separated the Pcb strains into 12 clusters, reflecting subdivision in terms of geographic origin, and Pcc isolates were clearly differentiated from Pcb isolates. A large degree of DNA polymorphism was evident among these 12 clusters. The study identified all the pathogens associated with the blackleg/soft rot disease complex.     

韭菜和辣椒间作对辣椒疫病的防治效果及其化感机理

为明确韭菜和辣椒间作对辣椒疫病的防治效果及其化感机理,比较了韭菜和辣椒不同行比间作对辣椒疫病的防治效果,测定了韭菜茎、叶挥发物与浸提液对辣椒疫霉菌的抑制作用,并分析了韭菜根系对辣椒疫霉菌游动孢子侵染和传播行为的影响。结果表明,韭菜与辣椒行比为3∶1间作能显著控制辣椒疫病的扩展与传播;2.0 g/皿韭菜茎挥发物及0.15 m L/m L茎浸提液对辣椒疫霉菌菌丝生长的抑制活性可达33.33%和88.75%;辣椒疫霉菌游动孢子对韭菜根系具有明显的趋化活性,且于根围迅速休止并萌发,丧失在土壤中继续寻找寄主的能力,其传播侵染行为受到干扰。研究表明,韭菜和辣椒间作可以有效控制辣椒疫病的扩展蔓延,实现对辣椒疫病的生态防控。     

葡萄卷叶相关病毒13在我国葡萄上的首次报道

<正>我国葡萄品种资源丰富,栽培面积逐年增加。葡萄感染病毒后,便终生带毒,持续危害,造成生长发育迟缓,树势衰退,严重影响葡萄的产量和品质。山葡萄(Vitis amurensis Rupr.)是我国重要的野生果树资源,其抗病能力较强,是培育抗病、抗寒优良品种的珍贵种质。山葡萄浆果营养物质丰富,是酿