The N-Terminal Region of the Readthrough Domain Is Closely Related to Aphid Vector Specificity of Soybean dwarf virus

ABSTRACT It has been speculated that the N-terminal half of the readthrough domain (RTD) encoded by open reading frame 5 of Soybean dwarf virus (SbDV) is related to the vector specificity. To further investigate this hypothesis, transmissibility via aphids was tested on 17 SbDV isolates and comparisons of the deduced amino acid sequences of the coat protein (CP) and other proteins encoded by the RTD were made between these isolates. Isolates were distinguished into four strains: YS, causing yellowing in soybean and transmittable by Aulacorthum solani; DS, causing dwarfing and transmittable by A. solani; YP, causing yellowing and transmittable by Acyrthosiphon pisum; and DP, causing dwarfing and transmittable by A. pisum. Phylogenetic analysis showed that the trees for the CP and the C-terminal half of the RTD sequences contained clusters of isolates of the same symptom type, whereas the tree for the N-terminal half of the RTD contained clusters of isolates of the same aphid vector type. These results agreed with our previous data of the complete nucleotide sequences of four SbDV isolates, and strongly indicated a close relationship between the N-terminal half of the RTD amino acid sequences and aphid transmission specificity of SbDV.     

Transmission, characterization, and serology of a luteovirus associated with yellow leaf syndrome of sugarcane

ABSTRACT A previously uncharacterized luteovirus was associated with one form of yellow leaf syndrome (YLS), a widespread disease of sugarcane (Saccharum sp.). The virus was named Sugarcane yellow leaf luteovirus (ScYLV), and was identified in major sugarcane-producing areas of the world. Typical disease symptoms were reproduced when ScYLV was transmitted by Melanaphis sacchari or Rhopalosiphum maidis from infected to healthy sugarcane, suggesting that this virus may be the causal agent of one form of YLS. The only known hosts of ScYLV are Saccharum and Erianthus spp. Virions of ScYLV were 24 to 29 nm in diameter in sodium phosphotungstate at pH 5.0, had a buoyant density of 1.30 g/cm(3) in Cs(2)SO(4), and contained a 5.8-kb genomic ssRNA. The capsid protein had an estimated relative molecular mass of 27 kDa and was not glycosylated. A polyclonal rabbit antiserum raised against ScYLV did not detect any of eight other luteoviruses by enzyme-linked immunosorbent assay or immunosorbent electron microscopy, but in immunoblot assays, antibodies to ScYLV detected the RPV serotype of Barley yellow dwarf luteovirus. It is concluded that ScYLV is a previously undescribed luteovirus that is biologically and serologically distinct from other members of the group and may be the causal agent of one form of YLS of sugarcane.     

陕西韩城严重发生的小麦矮缩病病原鉴定与原因分析

2007年在陕西韩城发现一种新的小麦病毒病害,症状表现为严重矮缩、黄化、条斑和分蘖增多等,发病面积约0.07万hm²,病田减产达50%,严重地块甚至绝收。本研究通过对采集自我国陕西韩城的7个样品进行PCR鉴定、全基因组序列测定及比较,证实陕西韩城样品确是小麦矮缩病毒(WDV)侵染所致,并对发病原因及其流行趋势进行了分析。这是小麦矮缩病在我国麦田大发生的首次报道。     

Phylogeny of Egyptian isolates of <Emphasis Type="Italic">Cucumber mosaic virus</Emphasis> (CMV) and <Emphasis Type="Italic">Tomato mosaic virus</Emphasis> (ToMV) infecting <Emphasis Type="Italic">Solanum lycopersicum</Emphasis>

Four Cucumber mosaic virus (CMV) (CMV-HM 1–4) and nine Tomato mosaic virus (ToMV) (ToMV AH 1–9) isolates detected in tomato samples collected from different governorates in Egypt during 2014, were here characterized. According to the coat protein gene sequence and to the complete nucleotide sequence of total genomic RNA1, RNA2 and RNA3 of CMV-HM3 the new Egyptian isolates are related to members of the CMV subgroup IB. The nine ToMV Egyptian isolates were characterized by sequence analysis of the coat protein and the movement protein genes. All isolates were grouped within the same branch and showed high relatedness to all considered isolates (98–99%). Complete nucleotide sequence of total genomic RNA of ToMV AH4 isolate was obtained and its comparison showed a closer degree of relatedness to isolate 99–1 from the USA (99%). To our knowledge, this is the first report of CMV isolates from subgroup IB in Egypt and the first full length sequencing of an ToMV Egyptian isolate.     

引起玉米粗缩病的水稻黑条矮缩病毒山东分离物的分子特性

 Four isolates of Rice black-streaked dwarf virus (RBSDV) were collected from the maize plants showing rough dwarf symptom in Linyi and Tai'an,Shandong province.The S10 genomic sequences of these isolates were determined and compared with those of 14 other RBSDV isolates.All of the four sequences were 1 801 base pairs (bp) long including the 5'-UTR of 21 bp and the 3'-UTR of 103 bp.They all contained an open reading frame of 1 677 bp (22-1698),encoding the coat protein (CP) of 558 amino acids.The sequences of these four RBSDV isolates and those of the major cp gene of 14 other isolates available in the GenBank were divided into two groups in the phylogenetic tree.Recombination analysis indicated that the isolate Lym2 was likely a recombinant of isolates Lym1 and Zhjs.     

甘蔗花叶病毒2个山东分离物的全基因组序列分析

甘蔗花叶病毒(Sugarcane mosaic virus,SCMV)是引起我国玉米矮花叶病的主要病毒。本文从山东泰安采集到2个表现矮花叶症状玉米样品的分离物(命名为DWK1和DWK2),通过RT-PCR扩增全基因组片段并测定了其序列(GenBank登录号分别为KU171814和KU171815)。序列分析结果表明,DWK1和DWK2基因组全长分别为9 575和9 576个核苷酸(nucleotides,nt),开放阅读框均为9 192 nt,编码3 063个氨基酸的多聚蛋白。DWK1和DWK2的全基因组核苷酸一致率为81.7%,DWK1与山西分离物SX(AY569692)的核苷酸一致率最高,为90.9%;DWK2与河北分离物BD8(JN021933)核苷酸一致率最高,达99.4%。二者在系统进化树中分别被聚类到Ⅰ组和Ⅳ组。重组分析发现,DWK1是HN(AF494510)、Guangdong(AJ310105)和BD8 3个分离物的重组体。选择压力分析表明,SCMV 11个蛋白的dN/dS值都小于1,均处于负选择,但在P1、P3和CP中存在正选择位点。本研究结果可为甘蔗花叶病毒株系的监测及防控提供理论指导。     

First report of barley yellow dwarf luteovirus onMiscanthus in the United Kingdom

Barley yellow dwarf luteovirus (BYDV) was detected in field grownMiscanthus sacchariflorus propagated from root cuttings. Inoculation of BYDV toM. sinensis plants grown from seed had an adverse effect on shoot growth and leaf development.     

Phylogenetic relationships between rice dwarf phytoreovirus isolates from five countries

Rice dwarf virus isolates were collected from several locations in Japan, the Philippines, China, Nepal and Korea. Genomic dsRNA segment profiles in polyacrylamide gel electrophoresis differed among the isolates. There were less differences in the profiles between isolates from Japan and Korea than in those between these two Countries and others. Nucleic acid hybridization was used to examine the extent of genomic variation. Full-length cDNAs to all genomic segments encoding non-structural proteins (S4, S6, S9, S10, S11 and S12) were synthesized from two Japanese isolates, and were used for dot-blot hybridization. Hybridizations using probes generated from the full-length cDNA clones failed to differentiate isolates from different geographical areas. However, cDNA probes covering a variable region of S12 were able to distinguish Japanese and Korean isolates from those of other countries. Phylogenetic tree analysis based on the amino acid sequence of P12 encoded by S12 grouped Japanese and Korean isolates together. The Chinese isolates from two different locations (Yunnan and Fujian) were closely related to each other, and were the most distantly related to Japanese and Korean isolates.     

Production and evaluation of monoclonal antibodies for the detection of beet mild yellowing luteovirus and related strains

A sugar-beet-infecting isolate of beet mild yellowing luteovirus (BMYV), and aBrassica-infecting isolate of beet western yellows luteovirus (BWYV) were used to produce monoclonal antibodies for epidemiological studies with BMYV and related field strains. Thirty-four monoclonal antibodies were tested for their reaction with 9 luteoviruses in triple-antibody-sandwich enzyme-linked immunosorbent assay. One (MAFF 24) is now routinely used in the UK for detecting BMYV and BWYV in plants and aphids, although it does not discriminate between them. Heterologous reactions were detected between some of the monoclonal antibodies and potato leafroll virus (PLRV), bean leafroll virus (BLRV) and barley yellow dwarf virus (BYDV-RPV). 38% of antibodies raised to BWYV reacted with PLRV compared with 4% of those raised to BMYV. Monoclonal antibodies were produced which distinguished a sugar-beet-infecting isolate of BMYV with differing host range and serological properties from the commonly-occurring field strain.     

Outbreak of MAV-type barley yellow dwarf virus on wheat in the Garhwal Hills in India

A serious outbreak of barley yellow dwarf luteovirus (BYDV, MAV-type) on wheat in the Garhwal Hills, Central Himalayas, India is reported. This is the first conclusive evidence based on serology for the presence of MAV-BYDV in India.     

First report of tomato chlorotic dwarf viroid isolated from symptomless petunia plants (Petunia spp.) in Japan

A viroid was detected for the first time in symptomless petunia plants (Petunia spp.) and identified as Tomato chlorotic dwarf viroid (TCDVd) based on an analysis of the complete genomic sequence. These petunia plants are a likely source of inoculum for tomato or potato plants because TCDVd induces severe symptoms on these plants. The genomic sequence of this petunia isolate from Japan shared 100 % identity with petunia isolates from the Netherlands and United Kingdom and a tomato isolate from Japan. Phylogenetic analysis showed that all petunia isolates and the tomato isolate from Japan formed a monophyletic clade.     

大豆枯萎病菌尖孢镰孢遗传多样性及大豆品种抗性

 了解大豆枯萎病菌的群体遗传特征及明确大豆种质对大豆枯萎病的抗性,对抗病育种、抗性品种的合理布局以及制定更有效的病害防治策略具有重要的参考价值。本研究利用随机扩增多态性DNA(random amplified polymorphic DNA,RAPD),对采自我国不同地区的大豆枯萎病菌—尖孢镰孢菌(Fusarium oxysporum)进行遗传多样性分析,筛选到10个多态性随机引物,共扩增出75条RAPD条带,其中55条为多态性条带,占73.3%。利用UPGMA法对DNA扩增图谱进行聚类分析,以相似系数0.68为阈值,55个分离物可分为9个遗传聚类组,表明我国大豆枯萎病菌具有丰富的种内遗传多样性,所划分的群体与分离物来源地不相关。同时,对上述分离物进行致病性分析,发现我国的大豆枯萎病菌具有明显的致病力分化现象。进一步利用3个代表性分离物对来自我国不同大豆产区的180个大豆品种(资源)进行抗大豆枯萎病鉴定,发现皖豆28、中黄13、中黄51、中作X08076和5D034等5个品种对大豆枯萎病具有良好抗性,占供试材料的2.8%,表明不同大豆品种对枯萎病的抗性存在一定的差异。     

Specific resistance to soybean stem canker conferred by the Rdm4 locus

The Rdm4 gene from soybean cv. Hutcheson has been extensively used to incorporate resistance to soybean stem canker (SSC), caused by Diaporthe phaseolorum var . meridionalis (Dpm), into soybean commercial cultivars. The objective of this work was to characterize the inheritance of the Rdm4 locus in different populations derived from the cross: J77-339 ( rdm / rdm , susceptible) × Hutcheson ( Rdm4 / Rdm4 , resistant) in independent interactions with two local isolates of Dpm. Four F₂ populations were obtained and two were advanced to the F₃ generation as separate F_2:3 families to perform progeny tests. Each population was inoculated with the CE109 and/or CE112 isolates of Dpm. Within each plant–pathogen interaction, the resistance gene segregated as completely dominant. However, cross resistance, or opposite disease reactions, to CE109 and CE112 isolates of Dpm were observed in four F_2:3 families, indicating an intergenic recombination event between two nonallelic genes interacting specifically with each isolate of Dpm. The distance between them, estimated as the recombination fraction, was 29%, suggesting that both genes were not tightly linked, but close enough to segregate together in most crosses. Results indicated the existence of a genomic region in cv. Hutcheson composed of race-specific resistance loci with at least two Rdm genes: the previously recognized Rdm4 and a novel gene, tentatively named Rdm5 , conferring specific resistance to Dpm isolates CE109 and CE112.     

Host Specialization in the Charcoal Rot Fungus, Macrophomina phaseolina

ABSTRACT To investigate host specialization in Macrophomina phaseolina, the fungus was isolated from soybean, corn, sorghum, and cotton root tissue and soil from fields cropped continuously to these species for 15 years in St. Joseph, LA. Chlorate phenotype of each isolate was determined after growing on a minimal medium containing 120 mM potassium chlorate. Consistent differences in chlorate sensitivity were detected among isolates from different hosts and from soil versus root. To further explore genetic differentiation among fungal isolates from each host, these isolates were examined by restriction fragment length polymorphism and random amplified polymorphic DNA (RAPD) analysis. No variations were observed among isolates in restriction patterns of DNA fragments amplified by polymerase chain reaction covering the internal transcribed spacer region, 5.8S rRNA and part of 25S rRNA, suggesting that M. phaseolina constitutes a single species. Ten random primers were used to amplify the total DNA of 45 isolates, and banding patterns resulting from RAPD analysis were compared with the neighbor-joining method. Isolates from a given host were genetically similar to each other but distinctly different from those from other hosts. Chlorate-sensitive isolates were distinct from chlorate-resistant isolates within a given host. In greenhouse tests, soybean, sorghum, corn, and cotton were grown separately in soil infested with individual isolates of M. phaseolina that were chosen based on their host of origin and chlorate phenotype. Root colonization and plant weight were measured after harvesting. More colonization of corn roots occurred when corn was grown in soil containing corn isolates compared with isolates from other hosts. However, there was no host specialization in isolates from soybean, sorghum, or cotton. More root colonization in soybean occurred with chlorate-sensitive than with chlorate-resistant isolates.     

Variation in transmission of two BYDV-MAV isolates by multiple clones of Rhopalosiphum padi L.

Vector efficiency of up to 17 Rhopalosiphum padi L. clones originating from Europe, North America and North Africa, was evaluated by transmitting two isolates of the serotype MAV for which this species is normally an inefficient vector. When test plants were inoculated by batches of 3 aphids, both isolates were rather well transmitted by one clone (Rp5), isolate MAV2 was poorly transmitted by all other clones tested and isolate MAV11 was not transmitted by eight clones and poorly transmitted by two clones. When eight aphids were used by test plants, all clones transmitted both isolates. The epidemiological consequences of MAV transmission by some R. padi clones are discussed, as well as the interest of these clones for studying aphid-derived components of luteovirus transmission.     

蒙城大豆疫霉菌的鉴定及其生理小种

 在安徽省蒙城县对大豆疫霉根腐病的发生情况进行调查。应用选择性培养基对类似大豆疫霉根腐病症状的病株进行病原菌分离,在春大豆蒙城早熟青豆病株上分离到2株疫霉菌PMC1、PMC2和一些Fusarium spp.,在夏大豆上分离到的主要病原菌为Pythium spp.和Fusarium spp.,未分离到疫霉菌。根据疫霉菌分离物PMC1和PMC2形态和生理学特征以及对大豆的专化致病性,2个分离物被鉴定为大豆疫霉菌(Phytophthora sojae Kaufmann&Gerdemann)。应用国际通用鉴别寄主进行生理小种鉴定,PMC1和PMC2的毒力公式分别为1b,1d,3a,3c,5,7和1b,1d,4,5,为新的小种类型,定名为中国6号小种、中国7号小种(CNR-6和CNR-7)。这是首次报道大豆疫霉菌在我国淮北地区存在。     

Rapid and Sensitive Detection of Phytophthora sojae in Soil and Infected Soybeans by Species-Specific Polymerase Chain Reaction Assays

ABSTRACT Root and stem rot caused by Phytophthora sojae is one of the most destructive diseases of soybean (Glycine max) worldwide. P. sojae can survive as oospores in soil for many years. In order to develop a rapid and accurate method for the specific detection of P. sojae in soil, the internal transcribed spacer (ITS) regions of eight P. sojae isolates were amplified using polymerase chain reaction (PCR) with the universal primers DC6 and ITS4. The sequences of PCR products were aligned with published sequences of 50 other Phytophthora species, and a region specific to P. sojae was used to design the specific PCR primers, PS1 and PS2. More than 245 isolates representing 25 species of Phytophthora and at least 35 other species of pathogens were used to test the specificity of the primers. PCR amplification with PS primers resulted in the amplification of a product of approximately 330 bp, exclusively from isolates of P. sojae. Tests with P. sojae genomic DNA determined that the sensitivity of the PS primer set is approximately 1 fg. This PCR assay, combined with a simple soil screening method developed in this work, allowed the detection of P. sojae from soil within 6 h, with a detection sensitivity of two oospores in 20 g of soil. PCR with the PS primers could also be used to detect P. sojae from diseased soybean tissue and residues. Real-time fluorescent quantitative PCR assays were also developed to detect the pathogen directly in soil samples. The PS primer-based PCR assay provides a rapid and sensitive tool for the detection of P. sojae in soil and infected soybean tissue.     

Pathogenic races of soybean rust Phakopsora pachyrhizi collected in Tsukuba and vicinity in Ibaraki,Japan

Six races were identified among 26 single-lesion isolates of Phakopsora pachyrhizi from rust-infected leaves of nine samples of cultivated soybean and one sample of the wild host plant kudzu (Pueraria lobata) collected in Tsukuba and vicinity in Ibaraki, Central Honshu, Japan. Six races were detected on soybean cultivars and four races on kudzu. When two or more isolates obtained from the same samples were examined, the isolates were different races except from two samples. These results indicate that two or more races may be distributed on the same soybean cultivar and that the same races share soybean and kudzu hosts.     

Morphological and molecular characterization of the sudden-death syndrome pathogen of soybean in Brazil

Brazilian Fusarium isolates causing soybean sudden death syndrome (SDS) were characterized by comparing them with other Fusarium isolates associated with soybean root rot, as well as F. solani f.sp. glycines isolates associated with the disease in the USA, using molecular (mitochondrial and nuclear rDNA), morphological, cultural and pathogenic characteristics. On the basis of pathogenicity data, and restriction fragment length polymorphism and sequence analysis of the rDNA internal transcribed spacer (ITS) regions, isolates formed a group distinct from nonSDS F. solani isolates, as well as other Fusarium species. ITS sequence analysis also revealed that Brazilian isolates were distinct from the majority of SDS pathogens from the USA ( Fusarium virguliforme ) and conformed to Fusarium tucumaniae .