Genetic Characterization of Differential Reactions Among Host Group 3 Common Bean Cultivars to NL-3 K Strain of Bean common mosaic necrosis virus

ABSTRACT A previously unrecognized recessive resistance gene (or allele) was identified in three host group (HG) 3 common bean (Phaseolus vulgaris) cvs. Olathe, Victor, and UI 37, based on genetic analysis of plants from five populations screened with the NL-3 K strain of Bean common mosaic necrosis virus (BCMNV). The gene (or allele) was associated with resistance to leaf stunting and deformity and reduction in plant height. The gene (or allele) provides similar, but slightly better resistance than the bc-1(2) gene that is characteristic of HG 3 cultivars. Traditional HG 3 cultivars like Redlands Greenleaf B with bc-1(2) are susceptible to NL-3 K, whereas this newly identified gene (or allele) conditions resistance to NL-3 K. Other slight variations in disease reaction pattern to a wide array of bean common mosaic (BCM)-inducing strains were noted among HG 3 differentials, indicating that additional resistance to BCM exists in common bean that remains to be exploited. To gauge the full breeding value of this newly identified gene (or allele), allelism tests with existing genes, namely bc-1(2), and further characterization of responses to all Bean common mosaic virus (BCMV) and BCMNV strains need to be conducted. Meanwhile, breeders should consider introgressing this more effective gene (or allele) into susceptible cultivars while plant pathologists continue to decipher the genetic variability present among HG 3 differential cultivars.     

Characterization of <Emphasis Type="Italic">Bean common mosaic virus</Emphasis> and <Emphasis Type="Italic">Bean common mosaic necrosis virus</Emphasis> isolates in common bean growing areas in Turkey

Bean common mosaic virus (BCMV) and Bean common mosaic necrosis virus (BCMNV) are well-known legume-infecting potyviruses. The incidences of BCMV and BCMNV infections were determined by ELISA in 367 seed and leaf samples which were collected in 15 common bean-growing provinces of Turkey. Of the samples tested, 67 (18.2 %) occurred to be infected with BCMV, however only 5 (1.4 %) were infected with BCMNV. A total of 45 ELISA-positive samples were selected from single-virus infected ones to determine BCMV and BCMNV pathogenicity groups (PGs) by using a set of bean cultivars that contain different combinations of resistance genes. Some BCMV populations exhibiting unusual pathogenicity were identified. One of them, named TR-180, was found to overcome resistance conferred by bc-1, bc-1 ² , bc-2 and bc-2 ² recessive alleles in common bean and assigned to PG VII. This isolate shared high (99 %) sequence identity with previously identified BCMV RU-1 and RU-1-related strains (RU1-OR-B and RU1-OR-C) according to a BLAST analysis of the nucleotide sequences of RT-PCR amplified products comprising the complete coat protein and 3′ partial NIb regions. The isolates TR-203 and TR-256 produced a distinctive reaction pattern in the dominant I gene-bearing bean cultivars Amanda and Isabella at lower (<30 °C) temperatures and were classified into PG IVb. These isolates were found to be 99 % identical to US-1 strain based on 3′ terminal nucleotide sequences of the BCMV genome. A fourth isolate, TR-243, involved mixed BCMV populations, as confirmed by partial nucleotide sequence analysis; one was classified as belonging to PG VII being similar to TR-180, and another was assigned to PG IVb. In conclusion, on the basis of both the reactions of differential bean cultivars and ELISA results, most of BCMV isolates were assigned to pathogroup PG VII and BCMNV isolates to PG VIb. This study is the first to show that four recessive resistance alleles of common bean can be overcome by a single field isolate of BCMV, and that a wide range of BCMV pathogroups are present in Turkey.     

Pathogenic and coat protein characterization confirming the occurrence of Bean common mosaic virus on common bean (Phaseolus vulgaris) in Kashmir,India

Bean common mosaic virus (BCMV), belonging to the family Potyviridae, is a serious pathogen of common bean (Phaseolus vulgaris L.) causing considerable economic losses owing to seed, sap and aphid transmissibility. The viral nature of the test isolates and identity of the virus as BCMV were confirmed by mechanical transmission and DAS-ELISA using BCMV antiserum. Pathogenic variability studies in BCMV infecting common bean (Phaseolus vulgaris L.) in Jammu and Kashmir (a northwestern Himalayan state of India), revealed the existence of three pathogroups – PG-I, PG-II and PG-VII, accommodating five strains (NL-1, NL-1n, NL-4, NL-7 and NL-7n). Comparative sequence analysis of coat protein gene revealed that the strains NL-1, NL-4 and NL-7 shared more than 90% amino acid sequence homology with other BCMV isolates from other countries. DAG motif as well as BCMV specific conserved motif MVWCIDN were present in all the three strains. Phylogenetic analysis of coat protein also clustered them in the BCMV group. This study confirmed the occurrence of BCMV and its strains on common bean in Kashmir.     

A Quantitative Method to Screen Common Bean Plants for Resistance to Bean common mosaic necrosis virus

ABSTRACT A quantitative method to screen common bean (Phaseolus vulgaris) plants for resistance to Bean common mosaic necrosis virus (BCMNV) is described. Four parameters were assessed in developing the quantitative method: symptoms associated with systemic virus movement, plant vigor, virus titer, and plant dry weight. Based on these parameters, two rating systems (V and VV rating) were established. Plants from 21 recombinant inbred lines (RILs) from a Sierra (susceptible) x Olathe (partially resistant) cross inoculated with the BCMNV-NL-3 K strain were used to evaluate this quantitative approach. In all, 11 RILs exhibited very susceptible reactions and 10 RILs expressed partially resistant reactions, thus fitting a 1:1 susceptible/partially resistant ratio (chi(2) = 0.048, P = 0.827) and suggesting that the response is mediated by a single gene. Using the classical qualitative approach based only on symptom expression, the RILs were difficult to separate into phenotypic groups because of a continuum of responses. By plotting mean percent reduction in either V (based on visual symptoms) or VV (based on visual symptoms and vigor) rating versus enzyme-linked immunosorbent assay (ELISA) absorbance values, RILs could be separated clearly into different phenotypic groups. The utility of this quantitative approach also was evaluated on plants from 12 cultivars or pure lines inoculated with one of three strains of BCMNV. Using the mean VV rating and ELISA absorbance values, significant differences were established not only in cultivar and pure line comparisons but also in virus strain comparisons. This quantitative system should be particularly useful for the evaluation of the independent action of bc genes, the discovery of new genes associated with partial resistance, and assessing virulence of virus strains.     

The occurrence of bean common mosaic necrosis virus in wild and forage legumes in Uganda

Bean common mosaic necrosis virus (BCMNV) was isolated from Centrosema pubescens, Crotalaria incana, Lablab purpureus, Phaseolus lunatus, Senna bicapsularis, S. sophera, Vigna vexillata and an unidentified Crotalaria species growing in Uganda. Thirteen distinct isolates were characterized using symptoms, pathogenicity in differential bean cultivars, serology, immunosorbent electron microscopy, and seed and aphid transmission. Some isolates conformed with the characteristics of previously described strains of BCMNV but others showed novel properties. All isolates reinfected the natural host from which they were obtained. The origin and ecological significance of these isolates is discussed.     

Elimination of Bean common mosaic virus using an electrotherapy technique

Journal of Plant Diseases and Protection - Bean common mosaic virus (BCMV) is a major seed transmitted virus of common bean (Phaseolus vulgaris). The use of virus-free germplasm is a prerequisite...     

辽中地区西瓜花叶病病原的分子鉴定

 利用ELISA和RT-PCR方法对采自我国辽中地区的西瓜花叶病样品进行检测,表明其病原为黄瓜绿斑驳花叶病毒(Cucumber green mottle mosaic virus,CGMMV)。将此分离物(CGMMV-Wcn)的外壳蛋白基因克隆后进行序列分析,结果表明其cp基因由486个碱基组成,编码161个氨基酸,与已报道的其它分离物一致;CGMMV-Wcn所致症状与西瓜株系(CGMMV-W)相同,且二者cp基因的氨基酸序列完全一致,因此该分离物应为CGMMV-W。     

Phylogenetic relationships within the family potyviridae: wheat streak mosaic virus and brome streak mosaic virus are not members of the genus rymovirus

ABSTRACT The complete nucleotide sequence of wheat streak mosaic virus (WSMV) has been determined based on complementary DNA clones derived from the 9,384-nucleotide (nt) RNA of the virus. The genome of WSMV has a 130-nt 5' leader and 149-nt 3'-untranslated region and is polyadenylated at the 3' end. WSMV RNA encodes a single polyprotein of 3,035 amino acid residues and has a deduced genome organization typical for a member of the family Potyviridae (5'-P1/HC-Pro/P3/6K1/CI/6K2/VPg-NIa/NIb/CP-3'). Because WSMV shares with ryegrass mosaic virus (RGMV) the biological property of transmission by eriophyid mites, WSMV has been assigned to the genus Rymovirus, of which RGMV is the type species. Phylogenetic analyses were conducted with complete polyprotein or NIb protein sequences of 11 members of the family Potyviridae, including viruses of monocots or dicots and viruses transmitted by aphids, whiteflies, and mites. WSMV and the monocot-infecting, mite-transmitted brome streak mosaic virus (BrSMV) are sister taxa and share a most recent common ancestor with the whitefly-transmitted sweet potato mild mottle virus, the type species of the proposed genus "Ipomovirus." In contrast, RGMV shares a most recent common ancestor with aphid-transmitted species of the genus Potyvirus. These results indicate that WSMV and BrSMV should be classified within a new genus of the family Potyviridae and should not be considered species of the genus Rymovirus.     

侵染美人蕉的CMV基因组全序列及其致病性分析

 对一株从美人蕉上分离到的CMV(Cah1-CMV)进行了全长克隆、全序列分析及寄主生物学研究。结果显示:其RNA1全长为3 356 nt,编码993个aa的1a蛋白;RNA2全长为3 045 nt,编码843 aa的2a蛋白和111 aa的2b蛋白;RNA3全长为2 220 nt,编码279 aa的3a蛋白和218 aa的CP蛋白。系统进化树分析显示:Cah1-CMV是CMV亚组IB株系。但是,该株系可以通过汁液摩擦接种侵染烟草(Nicotiana tabacum)、心叶烟(N.glutinosa)和番茄(Lycopersivon esculentum)鉴别寄主,可引起心叶烟顶端坏死,而在其他茄科寄主上均为典型花叶。将Cah1-CMV的2b替换到Fny-CMV中,产生FCah12b-CMV重组体,分析其在心叶烟上的致病性。结果显示:侵染早期,FCah12b-CMV引起心叶烟顶端叶黄褐坏死,与其母本病毒Cah1-CMV的症状相似,而非Fny-CMV症状;侵染后期,FCah12b-CMV并不引起植株系统性坏死。Northern blot-ting结果显示:Cah1-CMV、FCah12b-CMV和Fny-CMV在系统叶中的积累水平不存在明显差异。以上结果说明Cah1-CMV的2b基因在Cah1-CMV致病过程中具有重要功能,但并不是整株症状的决定因子;致病性差异与其基因组RNA在寄主体内的积累水平并不呈正相关性。     

The Complete Nucleotide Sequence and Biotype Variability of Papaya leaf distortion mosaic virus

ABSTRACT The complete nucleotide sequence of the genome of Papaya leaf distortion mosaic virus (PLDMV) was determined. The viral RNA genome of strain LDM (leaf distortion mosaic) comprised 10,153 nucleotides, excluding the poly(A) tail, and contained one long open reading frame encoding a polyprotein of 3,269 amino acids (molecular weight 373,347). The polyprotein contained nine putative proteolytic cleavage sites and some motifs conserved in other potyviral polyproteins with 44 to 50% identities, indicating that PLDMV is a distinct species in the genus Potyvirus. Like the W biotype of Papaya ringspot virus (PRSV), the non-papaya-infecting biotype of PLDMV (PLDMV-C) was found in plants of the family Cucurbitaceae. The coat protein (CP) sequence of PLDMV-C in naturally infected-Trichosanthes bracteata was compared with those of three strains of the P biotype (PLDMV-P), LDM and two additional strains M (mosaic) and YM (yellow mosaic), which are biologically different from each other. The CP sequences of three strains of PLDMV-P share high identities of 95 to 97%, while they share lower identities of 88 to 89% with that of PLDMV-C. Significant changes in hydrophobicity and a deletion of two amino acids at the N-terminal region of the CP of PLDMV-C were observed. The finding of two biotypes of PLDMV implies the possibility that the papaya-infecting biotype evolved from the cucurbitaceae-infecting potyvirus, as has been previously suggested for PRSV. In addition, a similar evolutionary event acquiring infectivity to papaya may arise frequently in viruses in the family Cucurbitaceae.     

Bean golden yellow mosaic virus from Chiapas, Mexico: Characterization, Pseudorecombination with Other Bean-Infecting Geminiviruses and Germ Plasm Screening

ABSTRACT The complete nucleotide (nt) sequences of the cloned DNA-A (2644 nts) and DNA-B (2609 nts) components of Bean golden yellow mosaic virus (BGYMV-MX) from Chiapas, Mexico were determined. The genome organization of BGYMV-MX is similar to that of other Western Hemisphere bipartite geminiviruses (genus Begomovirus). Infectivity of the cloned BGYMV-MX DNA components in common bean (Phaseolus vulgaris) plants was demonstrated by particle bombardment and agroinoculation. BGYMV-MX was identified as a BGYMV (previously type II BGMV) isolate based on sequence analyses, sap-transmissibility, and pseudorecombination experiments with other bean-infecting begomoviruses. On the basis of differences in the DNA-B hypervariable region, symptom phenotype, and properties of infectious pseudorecombinants, BGYMV-MX may represent a distinct strain of BGYMV. Pseudorecombination experiments further established that BGYMV symptom determinants mapped to DNA-B, and that BGYMV-MX was most closely related to BGYMV from Guatemala. A Tomato leaf crumple virus (TLCrV) DNA-A/BGYMV-MX DNA-B pseudorecombinant was infectious in bean, establishing that a viable reassortant can be formed between begomovirus species from different phylogenetic clusters. Bean germ plasm representing the two major gene pools (Andean and Mesoamerican) was screened for response to BGYMV-MX with three methods of inoculation: sap-inoculation, particle bombardment, and agroinoculation. Andean germ plasm was very susceptible and similar results were obtained with all three methods, whereas Mesoamerican germ plasm showed resistance to BGYMV-MX, particularly with agroinoculation.     

烟草花叶病毒及其弱毒株基因组的cDNA克隆和序列分析

 利用RT-PCR技术获得了覆盖整个烟草花叶病毒(Tobacco mosaic virus,TMV)强毒株TMV-W、2个弱毒株TMV-017和TMV-152基因组(RNA)的cDNA克隆。序列测定结果表明,强、弱毒株全长均为6 395个核苷酸,具有4个开放阅读框(open readingframe,ORF),分别编码126、183、30、17.6 kDa蛋白。TMV-W和普通株系TMV-U1的基因组同源率达到98%,TMV-W为普通株系。TMV-017、TMV-152基因组发生变异的部位主要在126/183 kDa ORF中。和TMV-W相比,TMV-017仅在126 kDa蛋白ORF中有18个碱基发生变异,其中10个碱基引起氨基酸的改变;而TMV-152在183 kDa ORF中有16个碱基发生变异,其中有11个引起氨基酸的改变。TMV-017和TMV-152有11个共同变异的碱基,其中有8个引起氨基酸的变异。TMV-152在30 kDa ORF中有1个碱基发生变异而引起氨基酸的改变。其它区域,三者完全相同。     

Characterization of symptom determinants in two mutants of cucumber mosaic virus Y strain,causing distinct mild green mosaic symptoms in tobacco

Two mutants of Cucumber mosaic virus, CMV(Y/GM1) and CMV(Y/GM2), which induced mild green mosaic symptoms in tobacco, were isolated from plants regenerated from tobacco leaves with yellow mosaic symptoms originally infected with the yellow strain of CMV [CMV(Y)]. Although the appearance of mild green mosaic symptoms in tobacco infected with CMV(Y/GM2) was unstable, CMV(Y/GM3) derived from CMV(Y/GM2) reproducibly induced mild green mosaic symptoms in tobacco similar to CMV(Y/GM1). A comparison of the deduced amino acid sequences of the coat proteins of CMV(Y), CMV(Y/GM1) and CMV(Y/GM3), showed single amino acid substitutions from Thr to Ile at position 124 in the CMV(Y/GM1) coat protein and from Val to Ile at position 111 in the CMV(Y/GM3) coat protein. When the amino acid at the 124 or 111 position in the CMV(Y) coat protein was changed to Ile at the cDNA level, CMV RNA3 transcribed in vitro from each cDNA induced mild green mosaic symptoms in tobacco after inoculation with in vitro transcribed CMV(Y) RNA1 and RNA2. The results indicated that amino acids at positions 111 and 124 in the coat protein were responsible for the phenotypic changes caused by the two CMV isolates.     

Gentian mosaic virus: A New Species in the Genus Fabavirus

ABSTRACT A viral isolate, designated N-1 and obtained from a gentian (Gentiana scabra) plant that exhibited mosaic symptoms, was transmitted mechanically to nine plant species in six families. These plants are known as hosts of fabaviruses. The N-1 isolate was composed of isometric particles 30 nm in diameter and included two RNA molecules of approximately 6.0 and 3.6 kb in length, as estimated by agarose gel electrophoresis. The RNAs were encapsidated separately in two of the three types of particle. Each particle contained two distinct proteins with Mr values of 39.3 x 10(3) and 26.6 x 10(3), as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Analysis of complete nucleotide sequences of the RNAs suggested that each encoded a single large polyprotein, in which putative functional proteins were arranged in a manner similar to those in Broad bean wilt virus 1 (BBWV-1) and Broad bean wilt virus 2 (BBWV-2), which are members of the genus Fabavirus (family Comoviridae). Analysis of the deduced amino acid sequences of the proteins indicated that those of isolate N-1 shared 38 to 66% identity with those of BBWV-1 and BBWV-2 but only 16 to 42% identity with those of a comovirus, Cowpea mosaic virus. Phylogenetic analysis, based on the amino acid sequences of RNA polymerase, placed isolate N-1 in a separate lineage from BBWV-1 and BBWV-2. In indirect-enzyme-linked immunosorbent assay, isolate N-1 exhibited distant serological relationship to BBWV-1, BBWV-2, and Lamium mild mosaic virus, another fabavirus. Our results suggest that N-1 represents a new species of Fabavirus. We propose the name Gentian mosaic virus for this new species.     

Serotypic variation in turnip mosaic virus

A panel of 30 monoclonal antibodies (MAbs) was produced against four isolates of turnip mosaic virus (TuMV). The panel was tested in plate-trapped antigen ELISA tests against 41 TuMV isolates (with different host and geographical origins and of differing pathotypes). The antibodies were also tested against four other potyviruses (bean common mosaic virus, bean common mosaic necrosis virus, lettuce mosaic virus and zucchini yellow mosaic virus). The reactions were assessed quantitatively (using multivariate analysis) and qualitatively (using the standard deviation obtained against healthy leaf material). The MAbs recognized 16–17 TuMV epitopes that were not present in the other potyviruses and a further two potyvirus epitopes. The isolates were grouped into three serotypes. Only one isolate did not fit this grouping. The classification of seven isolates in coat protein amino acid sequence homology groups correlated with serotypes. There was no correlation between serotype and pathotype, or between reactions to individual MAbs and single lines. There was therefore no evidence that the epitopes recognized by the MAbs are elicitors for the resistance genes present in the Brassica napus lines. However, the sensitivity and specificity of the MAbs will be useful for both routine detection of TuMV and fundamental studies on plant–virus interactions.     

The complete nucleotide sequence of RNA2 of barley mild mosaic virus (BaMMV)

Barley mild mosaic virus is a member of theBymoviruses, a genus of the familyPotyviridae. The virus consists of two types of flexuous rod-shaped particles. Each of them contains one single-stranded polyadenylated RNA in plus orientation of approximately 7.6 kb (RNA1) and 3.6 kb (RNA2). Complementary DNAs of both RNAs have been synthesised and cloned. The nucleotide sequence of RNA2 has been determined. It is 3524 nucleotides in length, excluding the 3 poly(A) tail, and contains one large open reading frame (2679 nts), coding for a polyprotein of approximately 98 kDa. There are indications that a putative proteolytic activity in the N-terminal part can cleave the polyprotein autocatalytically into a 25 kDa protein (putative proteinase) and a 73 kDa polypeptide of unknown function.     

First report of <Emphasis Type="Italic">Bean common mosaic virus</Emphasis> in yam bean [<Emphasis Type="Italic">Pachyrhizus erosus</Emphasis> (L.) Urban] in Indonesia

Severe mosaic with leaf malformation and green vein banding was observed on yam bean in West and Central Java, Indonesia. Virions of the causal virus were flexuous filaments, about 700 nm in length, with a coat protein of 30 kDa. The virus was transmitted by mechanical inoculation and by aphids in a nonpersistent manner. The nucleotide sequence of the coat protein gene had the highest identity with that of Bean common mosaic virus (BCMV, genus Potyvirus) isolate VN/BB2-5. Based on demarcation criteria, including the genome sequence and host range, we tentatively designate this isolate as BCMV-IYbn (Indonesian yam bean). The nucleotide sequence reported is available in the DDBJ/EMBL/GenBank databases under accession number AB289438.     

Possibility of Bean yellow mosaic virus detection in Gladiolus plants by different methods

Journal of Plant Diseases and Protection - Serological and molecular methods were compared for the detection of Bean yellow mosaic virus (BYMV) in gladiolus plants. Plants showing mosaic symptoms...     

Biotic, molecular, and phylogenetic characterization of bean calico mosaic virus, a distinct begomovirus species with affiliation in the squash leaf curl virus cluster

ABSTRACT Bean calico mosaic virus (BCMoV), a whitefly-transmitted geminivirus from Sonora, Mexico, was purified, and the genome components were cloned and sequenced. Purified viral fractions and cloned genome components were infectious by biolistic inoculation to bean, completing Koch's postulates for both. The B biotype of the whitefly Bemisia tabaci efficiently transmitted both native virus and progeny virus derived from cloned DNA inoculum. Host ranges of native virus and of progeny virus derived from cloned DNA were identical based upon whitefly and biolistic mediated transmission, respectively. BCMoV has a relatively wide experimental host range among begomoviruses known to infect bean, encompassing genera and species within the Fabaceae, Malvaceae, and Solanaceae. BCMoV has a bipartite genome, as do other New World begomoviruses. BCMoV DNA-A shared highest nucleotide sequence identities with squash leaf curl virus-E strain (SLCV-E) and cabbage leaf curl virus (CaLCV) at 80.1 and 80.7%, respectively. BCMoV DNA-B shared highest nucleotide sequence identity with SLCV-E at 70.7%. The common region (CR) sequences of BCMoV and SLCV-E are 73 to 76% identical; however, modular cis-acting elements within the CR involved in replication origin function and recognition are 100% conserved. Phy-logenetic analysis indicated that BCMoV DNA-A shares a most recent common ancestor with the DNA-A of two viruses that also occur in the Sonoran Desert, SLCV-E and Texas pepper virus (TPV-TAM), and CaLCV from Florida. In contrast, a phylogenetic analysis indicated that BCMoV DNA-B shares a most recent common ancestor with SLCV-E; whereas DNA-B of CaLCV clustered in a separate clade with pepper hausteco virus. Collectively, biological and molecular characteristics indicate that BCMoV is a distinct begomovirus species with the northernmost distribution of any begomovirus isolated from bean in the Americas. Furthermore, the phylogenetic relationships of begomovirus cognate components are not necessarily identical, suggesting that DNA-A and DNA-B of some begomoviruses may have different evolutionary histories.