Binucleate Rhizoctonia sp. AG G causing root rot in yacon (Smallanthus sonchifolius) in Brazil

A new rot caused by a binucleate Rhizoctonia sp. affecting the tuberous root cortex of the domesticated yacon ( Smallanthus sonchifolius ) has been observed in Brazil. Isolates of a binucleate Rhizoctonia sp. were collected from roots with rot symptoms and characterized by the number of nuclei per cell, hyphal anastomosis, RAPD molecular markers, ITS-5·8S rDNA sequence and pathogenicity tests. All isolates had a mean of 1·9–2·2 nuclei per cell and anastomosed with the binucleate Rhizoctonia sp. AG G-tester strain. RAPD analysis was carried out between 11 isolates recovered from yacon and 11 AG (A, Ba, Bb, Bo, C, D, F, G, O, P, Q) standard testers of binucleate Rhizoctonia sp. Genetic similarities of 94·8–100% were observed among isolates of the binucleate Rhizoctonia sp. from yacon and all isolates were genetically more closely related to the AG G tester than other strains according to upgma analysis using RAPD markers. Homologies of complete ITS nucleotide sequences were 100% between binucleate isolates of Rhizoctonia sp. from yacon and the AG G tester. According to pathogenicity tests, the isolates caused typical rot symptoms of yacon tubers 90 days after inoculation     

Identification of Rhizoctonia solani AG 1-IB in Lettuce, AG 4 HG-I in Tomato and Melon, and AG 4 HG-III in Broccoli and Spinach, in Brazil

Fungi isolated in Brazil, from lettuce, broccoli, spinach, melon and tomato, were identified as Rhizoctonia solani. All lettuce isolates anastomosed with both AG 1-IA and IB subgroups and all isolates from broccoli, spinach, melon and tomato anastomosed with AG 4 subgroup HG-I, as well as with subgroups HG-II and HG-III. DNA sequence analyses of ribosomal internal transcribed spacers showed that isolates from lettuce were AG 1-IB, isolates from tomato and melon were AG 4 HG-I, and isolates from broccoli and spinach were AG 4 HG-III. The tomato isolates caused stem rot symptoms, the spinach, broccoli and melon isolates caused hypocotyl and root rot symptoms on the respective host plants and the lettuce isolates caused bottom rot. This is the first report on the occurrence in Brazil of R. solani AG 4 HG-I in tomato and melon, of AG 4 HG-III in broccoli and spinach and of AG 1-IB in lettuce.     

草莓丝核菌根腐病的病原菌鉴定

 由丝核菌引起的根腐病是草莓生产上的重要病害之一。本研究基于形态学、菌丝细胞核荧光染色、菌丝融合群测定、rDNA-ITS序列分析和柯赫氏法则验证,对北京地区引起草莓根腐病的丝核菌进行了鉴定。2014年从北京市昌平区温室草莓根腐病病样中分离纯化获得的3个代表菌株,经形态学和细胞核荧光染色,确定均为双核丝核菌(binucleate Rhizoctonia, BNR),且与双核丝核菌AG-A融合群菌株发生菌丝融合,菌株CP-Z的rDNA-ITS序列与GenBank中丝核菌属的有性型角担菌属(Ceratobasidium)AG-A融合群 4个菌株的相似性达100%。菌株CP-Z接种草莓根部,引起根系变黑、腐烂,植株死亡,从接种发病的根部可重新分离到双核丝核菌。双核丝核菌AG-A融合群引起草莓根腐病为国内首次报道。该病原菌菌丝生长适温为25℃~28℃。     

Phytophthora oleae sp. nov. causing fruit rot of olive in southern Italy

A homothallic Phytophthora species was found to be consistently associated with a rot of mature fruits of two local cultivars of olive (Olea europaea) in Calabria, southern Italy. The phylogenetic analysis of sequences of the ITS1‐5.8S‐ITS2 region and cox1 gene enabled its identification as a new species of clade 2, with a basal position compared to previously described subclades. The new species is described formally with the epithet Phytophthora oleae, referring to the natural matrix from which it was isolated. A unique combination of molecular and morphological characters clearly separates P. oleae from other already described Phytophthora species. This new species produced semipapillate, occasionally bipapillate, persistent sporangia on simple sympodially branching sporangiophores as well as globose and smooth‐walled oogonia, paragynous antheridia and spherical, plerotic oospores. The pathogenicity of P. oleae was confirmed in inoculation trials on fruits of three olive cultivars, including the two local cultivars from which the pathogen had been isolated.     

朝鲜蓟细菌性根茎腐烂病病原的分离与鉴定

 在湖南省常德市西洞庭管区种植的朝鲜蓟（Cynara scolumus  L.）上发现了一种新的病害,其症状表现为地上部分从外层叶片开始逐步枯萎,随后根部和主茎杆的髓部腐烂变褐,最后整株枯萎。从田间感病朝鲜蓟茎杆的病健交界处用NA培养基分离,获得10个菌株,分别指定为HNXDT001~010,并进行了致病性测定、形态观察和细菌学特征分析,同时对HNXDT002菌株进行分子生物学鉴定。结果表明,该系列菌株在NA培养基上均形成灰白色圆形菌落,稍突起,有光泽,半透明。在显微镜下菌体呈短杆状,两端钝圆,具有2～8根周生鞭毛,革兰氏阴性。10个菌株通过针刺法接种均可导致朝鲜蓟茎杆、胡萝卜、辣椒、白菜、土豆、番茄和莴苣茎杆软腐,经科赫法则验证为致病病原菌。该菌株的16S rDNA序列和果胶酶基因片段测序(分别用16S rDNA通用引物16SF/16SR和果胶酶基因引物Y1/Y2扩增)与系统发育学分析表明,其16S rDNA序列(GenBank Accession No. JF721958)与胡萝卜软腐果胶杆菌胡萝卜亚种（Pectobacterium carotovorum  subsp.  carotovorum）菌株ATCC15713 (GenBank Accession No. U80197)序列同源性高达99％;果胶酶基因序列(GenBank Accession No. JF721960)与胡萝卜软腐果胶杆菌胡萝卜亚种（Pectobacterium carotovorum subsp. carotovorum）PC1菌株(GenBank Accession No. CP001657)序列同源性为93%。结果表明：朝鲜蓟细菌性根茎腐烂病病原为胡萝卜软腐果胶杆菌胡萝卜亚种。     

蝴蝶兰软腐病中一种新致病菌的分离与鉴定

 Soft rot disease often affects Phalaenopsis amabilis during the growing season. However, the pathogen of the disease is remaining poorly studied. In this study, bacterial strain R1 was isolated from soft rot tissues in Wuhan. The pathogenic, morphological, physiological, biochemical tests and 16S rDNA sequence analysis were carried out. The homology of 16S rDNA sequence between strain R1 and Pseudomonas grimontii was 99.72%, and its physiological and biochemical properties were also similar to those of Pseudomonas grimontiis. All these evidences indicated that strain R1 could be identified as a novel strain of Pseudomonas grimontii. The pathogenicity of the novel isolate was proved according to the Koch's postulates. This is the first report that Pseudomonas grimontii can cause soft rot disease of Phalaenopsis amabilis.     

Morphological,molecular phylogenetic and pathogenic analyses of Erysiphe spp. causing powdery mildew on cashew plants in Brazil

Cashew powdery mildew is presently the most important disease of cashew trees in all Brazilian growing regions. Although it was described over a century ago, it had never threatened the Brazilian cashew industry until the first decade of the 21st century. Morphological and pathogenic evidence indicated the possibility of different pathogen species being involved in early and late types of cashew powdery mildew. This study was designed to elucidate this issue by comparing two different powdery mildew fungi occurring on cashew plants in Brazil according to the morphological characteristics, phylogenetic relationships with closely related powdery mildew fungi and pathogenic relationships. Based on morphology, molecular phylogenetics and pathogenicity on cashew, it was shown that two species of powdery mildew specimens are without question associated with cashew trees. One species, which infects young immature tissues such as shiny leaves, flowers and young fruits, is Erysiphe quercicola, while Erysiphe necator is associated exclusively with mature leaves. This is the first report of both E. quercicola and E. necator causing cashew powdery mildew, and the first detection of E. necator on cashew.     

Characterization of isolates of binucleate Rhizoctonia spp. associated with strawberry black root rot complex using fatty acid methyl ester (FAME) profiles

Black root rot is an important disease of strawberry caused by a complex of fungi that includes species of Rhizoctonia. In this study, a modified MIDI method (Microbial Identification System) was investigated for its utility to differentiate isolates of the three different anastomosis groups (AGs) of binucleate Rhizoctonia spp., associated with strawberry black root rot complex representing AG-A, AG-G, and AG-I. A total of 11 fatty acids were detected, and the FAME profiles for isolates of the three different AGs of Rhizoctonia spp. varied quantitatively and qualitatively. Moreover, the modified MIDI method will be a useful discriminatory tool for fungal identification and classification of the AGs of binucleate Rhizoctonia spp. associated with strawberry black root rot complex.     

Genetic variation in Fusarium avenaceum causing root rot on field pea

Isolates of Fusarium spp. were recovered from the roots of field pea (Pisum sativum) collected from 15 commercial fields in Alberta, Canada. Most of the isolates (75 out of 96) were identified as F. avenaceum, based on morphology, phylogeny and species‐specific PCR amplification. Molecular differences in the F. avenaceum isolates were detected based on putative mating type, and on ITS and CPN60 sequences. MAT‐1 and MAT‐2 were equally distributed among the isolates. Phylogenetic analysis based on ITS and CPN60 sequences clustered most of the F. avenaceum isolates into a single group. In some cases, isolates with low aggressiveness clustered together in additional groups. There was no correlation between phylogenetic profile and either mating type or geographic origin. This population of F. avenaceum has a low level of genetic variation and consists of isolates derived from the two mating types. Isolates with low aggressiveness are also retained in the population.     

云南香石竹立枯病病原的鉴定及致病性研究

 27 Rhizoctonia solani isolates from carnation with damping-off symptoms were identified as anastomosis group AG-4 based on cultural characteristics and anastomosis in Yunnan.Sequence analysis of 5.8S rDNA-ITS of yx and tx presented 99% sequence similarity with AG-4 HGⅠtester isolate.Pathogenicity tests showed that isolates of AG-4 HG Ⅰ were pathogenic to carnation.This is the first record of damping-off of carnation caused by AG-4 HG Ⅰ in China.     

山西壶瓶枣缩果病病原菌分离和鉴定

 2005~2008年山西壶瓶枣缩果病害发生严重,造成了巨大的经济损失。本文利用真菌ITSrDNA和细菌16S rDNA基因的通用引物,分别对分离自山西晋中的罹病壶瓶枣果实表面寄生真菌和细菌基因组DNA进行PCR扩增,将扩增产物进行核苷酸序列测定,在GenBank数据库进行Megablast同源性分析,确定壶瓶枣果实的主要寄生菌是细极链格孢菌(Alternaria alternata)、白囊耙齿菌(Irpex lacteus)、青霉菌(Penicillium expansum)、芽枝孢菌(Cladosporium tenuissimum)4种真菌和枯草芽孢杆菌(Bacillus subtilis)、巨大芽孢杆菌(B.megaterium)、短小芽孢杆菌(B.pumilus)、多粘类芽孢杆菌(Paenibacillus polymyxa)4种细菌。回接试验证明链格孢菌、青霉菌、芽枝孢菌是壶瓶枣果实主要的致病真菌,而所分离的细菌没有致病性。     

利用28S rDNA D1/D2区和ITS rDNA序列鉴定甜瓜白粉病病原菌

为了明确宁夏干旱带压砂甜瓜白粉病病原菌,从病原菌分生孢子中提取DNA,PCR扩增ITSrDNA和28S rDNA D1/D2区段,测序后进行BLAST比对.结果表明,病原菌的ITS rDNA和28SrDNA D1/D2序列与菜豆叉丝单囊壳白粉菌Podosphaera phaseoli、凤仙花又丝单囊壳白粉菌P.bal-saminae、菊科叉丝单囊壳白粉菌P.fwca、苍耳单囊壳白粉菌P.xanthii、瓜类单囊壳白粉菌P.fuligi-nea等叉丝单囊壳属Podosphaera的多个种的ITS rDNA和28S rDNA D1/D2序列之间相似度均大于99%,鉴定甜瓜白粉病病原菌为叉丝单囊壳属Podosphaera.     

河北省甘薯茎腐病研究初报

甘薯茎腐病是近几年在我国发现的一种新的细菌性病害,目前该病已在我国的福建、广东、江西、广西、海南、河南、重庆、江苏等地发生。2013年10月在对河北省甘薯病害的调查中在文安县发现了大量疑似甘薯茎腐病的病株,给当地的甘薯生产造成了严重的影响。经对疑似病株病原菌的分离纯化、柯赫氏法则验证、形态观察以及基于16SrDNA序列的分析,最终确定该病害为甘薯茎腐病,病原菌为达旦提狄克氏菌(Dickeya dadantii)。这是该病害首次在河北省被发现。     

Grouping of Colletotrichum Species in Japan Based on rDNA Sequences

Internal transcribed spacers (ITS) of the ribosomal RNA gene (rDNA) were sequenced for 236 isolates covering 25 Colletotrichum species collected in Japan. The Japanese isolates could be grouped into 20 ribosomal groups (RGs) based on the sequences of ITS1, correlating the species identified by the morphology. Colletotrichum gloeosporioides sensu lato separated into three RGs that were morphologically different. Colletotrichum destructivum, C. linicola and C. higginsianum were possibly conspecific. Colletotrichum dematium sensu lato including C. capsici and other species that produce falcate conidia except for graminicolous ones were separated into three RGs that were difficult to distinguish morphologically. In the phylogenetic study using ITS2 and the 28S rDNA domain 2 region, topologies compiled by neighbor-joining and maximum-parsimony methods were almost the same, reflecting the conidial morphology. The phylogenetic group 1 (PG1) produced conidia with acute ends, e.g., C. acutatum, C. destructivum and C. graminicola; PG2 produced those with obtuse ends, e.g., C. gloeosporioides, and C. orbiculare. Colletotrichum theae-sinensis, which produced the smallest conidia, was grouped as PG3, far from other species, indicating it should not belong to Colletotrichum. Grouping and phylogenetic analysis using ribosomal DNA was an effective tool to classify and identify Colletotrichum species without using morphology. Received 15 July 2002/ Accepted in revised form 12 November 2002     

Identification of a new phytophthora species causing root and runner rot of cranberry in new jersey

ABSTRACT In New Jersey, Phytophthora cinnamomi is the pathogen most commonly isolated from diseased roots and runners of the cultivated cranberry (Vaccinium macrocarpon). A second distinct species of Phytophthora has been isolated from dying cranberry plants and surface irrigation water. This species is homothallic with paragynous antheridia and ellipsoid-limoniform, nonpapillate sporangia. It was tentatively identified as P. megasperma in an earlier report. Laboratory experiments demonstrate that the cardinal temperatures for vegetative growth are between 5 and 30 degrees C with an optimum near 25 degrees C. Sporangia are produced at temperatures between 10 and 20 degrees C with the majority of sporangia produced at 10 and 15 degrees C. In pathogenicity tests, no growth effect was observed on cranberry plants (cv. Early Black) when tests were conducted at 25 degrees C; however, significant reductions in plant growth occurred when tests were conducted at 15 degrees C. This species was insensitive to metalaxyl but was sensitive to buffered phosphorous acid. Sequence analysis of the internal transcribed spacer 1 (ITS1), 5.8S rDNA, and ITS2 regions place these isolates in Phytophthora clade 6 with greatest similarity to Phytophthora taxon raspberry. To our knowledge, this is the first report of isolates of this affiliation in North America. However, the observation of low temperature preferences makes this species unique in an otherwise high temperature clade. The isolates described in this study are tentatively classified as Phytophthora taxon cranberry.     

山西短颈剑线虫(Xiphinema brevicollum)形态与rDNA分子特征

采用浅盘分离法在山西太谷松树根际土壤中分离得到一种剑线虫,通过Seinhorst脱水制片后利用显微镜观察其形态特征并进行测量,其主要特征为:雌性虫体经热杀死后呈腹面弯曲的"C"形,体长1.71~2.26mm,两端渐细;齿针全长127.3~140.8μm;a(体长/体宽)为35.9~51.4μm,b(体长/食道外宽)为5.8~8.7μm,c(体长/尾长)为50.7~103μm。前卵巢与后卵巢长短相近,尾形近似圆锥形。未见雄虫。对该线虫的rDNA-ITS1,rDNAITS2和28SRNA序列进行扩增、测序及系统进化分析,结合形态学特征进行鉴定,将分离到的剑线虫鉴定为短颈剑线虫(Xiphinema brevicollum),这是山西首次发现报道剑线虫属的一个种。     

Molecular characterization of a phytoplasma causing Phyllody in Clover and other herbaceous hosts in Northern Italy

Red clover (Trifolium pratense) and Ladino clover (Trifolium repens) plants showing phytoplasma-associated symptoms (yellowing/reddening, virescence and phyllody) have been recovered in Friuli-Venezia Giulia, Italy. Using AluI RFLP analysis of PCR amplified 16S rDNA we showed that the disease can be caused independently by two phylogenetically distinct phytoplasmas. One of them showed the very typical 16S rDNA RFLP pattern of the agent of Clover Phyllody in Canada (CCPh). The 16S rDNA of the other phytoplasma (Italian Clover Phyllody phytoplasma, ICPhp) has been PCR amplified, cloned and sequenced. The sequence revealed high similarity (>98%) with phytoplasmas belonging to the X disease cluster, which includes organisms not reported to cause phyllody on their hosts. The analysis by AluI RFLP of the PCR amplified pathogen 16S rDNA from other herbaceous plants (Crepis biennis, Taraxacum officinale, Leucanthemum vulgare) collected nearby with phytoplasma-associated symptoms showed similar patterns. Southern blot hybridization of their EcoRI digested total DNA revealed identical RFLP patterns, suggesting that the causative agent may be the same organism.Abbreviations PCR Polymerase Chain Reaction - rDNA gene for the small subunit ribosomal RNA - RFLP Restriction Fragment Length Polymorphism     

非洲菊根腐病病原的鉴定与ITS序列分析

 从南京花卉苗圃的非洲菊腐烂病植株的根部分离到46株真菌菌株,将所有菌株回接到健康的植株上,结果发现只有11个疫霉菌菌株可以引起非洲菊典型的根腐病症状。对上述疫霉菌的形态特征、致病性及核糖体DNA-ITS序列进行分析,结果为所有菌株在LBA平板上菌落圆形、呈放射状、菌丝致密、气生菌丝较丰富、菌丝无隔,能形成大量菌丝膨大体,水培后产生大量椭圆形孢子囊,孢子囊无乳突,游动孢子在孢子囊内形成。进一步克隆并分析供试菌株核糖体DNA-ITS区域的序列,结果是分离菌株与GenBank中隐地疫霉的ITS序列的同源性均为99.87%,仅有1个碱基的差异,进一步明确了本研究中从非洲菊腐烂病植株根部分离的病原菌为隐地疫霉(Phytophthora cryptogea)。     

甘草根腐病病原菌鉴定

 甘草(Glycyrrhiza uralensis Fish.)别名甜草、蜜草、甜根子, 为豆科多年生草本植物, 以根与根茎入药, 具有补脾益气、清热解毒、祛痰止咳、缓急止痛、调和诸药之功效, 是我国临床常用的中药材, 也可用作食品添加剂。甘草主要分布在我国的内蒙古、甘肃和宁夏, 在青海、陕西、新疆、黑龙江、辽宁、吉林、河北、山西等地局部地区也有分布。宁夏盐池县是我国乌拉尔甘草的重要产区, 面积大、贮量多、品质好, 1995年被誉为“中国甘草之乡” ^[1]。近年来, 野生甘草遭到了大规模采挖, 甘草蕴藏量急剧减少, 目前主要通过人工种植来满足市场需求。随着甘草种植面积的不断扩大, 甘草病虫害日趋严重, 根腐病危害尤为突出, 直接影响甘草的产量和品质, 造成巨大经济损失。     

Influence of glyphosate on Rhizoctonia and Fusarium root rot in sugar beet

This study tests the effect of glyphosate application on disease severity in glyphosate-resistant sugar beet, and examines whether the increase in disease is fungal or plant mediated. In greenhouse studies of glyphosate-resistant sugar beet, increased disease severity was observed following glyphosate application and inoculation with certain isolates of Rhizoctonia solani Kuhn and Fusarium oxysporum Schlecht. f. sp. betae Snyd. & Hans. Significant increases in disease severity were noted for R. solani AG-2-2 isolate R-9 and moderately virulent F. oxysporum isolate FOB13 on both cultivars tested, regardless of the duration between glyphosate application and pathogen challenge, but not with highly virulent F. oxysporum isolate F-19 or an isolate of R. solani AG-4. The increase in disease does not appear to be fungal mediated, since in vitro studies showed no positive impact of glyphosate on fungal growth or overwintering structure production or germination for either pathogen. Studies of glyphosate impact on sugar beet physiology showed that shikimic acid accumulation is tissue specific and the rate of accumulation is greatly reduced in resistant cultivars when compared with a susceptible cultivar. The results indicate that precautions need to be taken when certain soil-borne diseases are present if weed management for sugar beet is to include post-emergence glyphosate treatments.