Strain Of Bean Yellow Mosaic Virus Research Articles

Phylogenetic analysis of a Bean yellow mosaic virus isolate from Iran and selecting the phylogenetic marker by comparing the individual genes and complete genome trees of BYMV isolates

Bean yellow mosaic virus (BYMV) is an economic potyvirus with worldwide distribution and a broad host range. Recently, phylogenetic studies of BYMV isolates have indicated the importance of comparing the full genome sequences to obtain a reliable classification. However, most available isolates in public databases are partially sequenced, and virologists continue to prefer partial genomes or individual genes for phylogenetic studies. As such, to avoid unbiased classification, phylogenetic studies should be based on either phylogenetic gene markers or a multigene dataset instead of just one random gene. In the present study, we sequenced the full genome of a BYMV isolate collected from an Iranian faba bean field using the Illumina Novaseq 6000 platform. The phylogenetic analysis revealed that the Iranian isolate is closely related to three isolates originating from faba bean fields in Japan, Australia and Germany. To identify the phylogenetic markers of BYMV, the topology distance between reconstructed trees based on individual genes and the whole genome was calculated using topology congruence tests considering only the topology of the compared trees and a character congruence test taking into account the characters, tree topology and estimated bootstrap support value. Accordingly, nuclear inclusion proteins a and b (NIa and NIb) and viral protein genome linked (VPg) were selected as evolutionary markers which can be used as appropriate representations of the full genome in phylogenetic studies. Furthermore, supermatrix approach was used to compare all BYMV isolates that have been fully or partially sequenced. The results demonstrate that all submitted BYMV strains can be divided into 10 main monophyletic clades with high bootstrap values; these are named BYM-1 through BYM-10 to avoid confusion with previously introduced nomenclature. Moreover, the results reveal that clustering based on phylogenetic analysis and their original host is not completely consistent, which supports recent phylogenetic studies based on available whole genome sequences.

Bean Yellow Mosaic Virus in Soybean from Argentina

AbstractAn association of Bean yellow mosaic virus (BYMV), (genus Potyvirus), with yellow mosaic leaf symptoms on soybean in Argentina was determined by enzyme‐linked immunosorbent assay, a result confirmed by transmission electron microscopy and reverse transcription‐polymerase chain reaction using a degenerate primer targeting the C‐terminal region of BYMV′s NIb. The sequence analysis showed that the isolate had 80.6–91.6% identities with other BYMV isolates from different strain groups, indicating that it is a strain of BYMV.

New Record of Association of Bean yellow mosaic virus with Mosaic Disease of Vicia faba in India

Faba bean (Vicia faba L.) is a species of bean belonging to the family Fabaceae extensively cultivated in Africa and Asia for its high nutritional values. In India and Nepal, it is called as “Bakulla”, its young pods are consumed as a green vegetable. It is used as human food in developing countries and as animal feed in industrialized countries. It is rich in l-dopa and used in medicine to treat Parkinson’s disease and to control hypertension (http://en.wikipedia.org/wiki/Vicia_faba). During a survey in February of 2011 severe mosaic symptoms were observed on about 35 % (38/109) V. faba plants growing in kitchen gardens at Lucknow. The symptoms were mild to severe (Fig. 1a) and infected plants were dwarf as compared to healthy plants. Since infection of Bean yellow mosaic virus (BYMV) is reported on V. faba [6], therefore, infection of potyvirus was suspected. Fig. 1 aBean yellow mosaic virus (BYMV) infected V. faba leaf showing mosaic symptoms. b Phylogenetic analysis of nucleotide sequence of Bean yellow mosaic virus isolate-1 ({type:entrez-nucleotide,attrs:{text:JF798580,term_id:341650451,term_text:JF798580}} ... For the detection of BYMV, total RNA was isolated from leaves of naturally infected V. faba plants from two locations using the RaFlex total RNA isolation kit (GeNei, India) and Reverse transcription-polymerase chain reaction (RT-PCR) were performed using a pair of degenerate primers (Pot 1 and Pot 2) capable of amplifying a 1.6–2.1 Kb fragment from 3′ end of the genome (virion protein gene and part of the NIb gene) of 17 species of the Potyviridae [4]. RT-PCR amplification resulted in the expected size (~1.6 Kb) amplicons from symptomatic V. faba (4/5) similar to a positive control (potyvirus infected gladiolus) but not from the healthy one. An additional specific band of ~0.8 Kb was also obtained in all the symptomatic samples. These results indicated presence of potyvirus infection in V. faba. For identification of potyvirus associated with mosaic symptoms of V. faba, the amplicons of ~1.6 Kb obtained from two symptomatic samples were sequenced directly and deposited in GenBank under Accession numbers: {type:entrez-nucleotide,attrs:{text:JF798580,term_id:341650451,term_text:JF798580}}JF798580 (isolate-1) and {type:entrez-nucleotide,attrs:{text:JN692500,term_id:779787813,term_text:JN692500}}JN692500 (isolate-2). BLASTn analysis of isolate-1 from V. faba ({type:entrez-nucleotide,attrs:{text:JF798580,term_id:341650451,term_text:JF798580}}JF798580) revealed highest sequence identities 87 % with polyprotein gene of various BYMV strains: from Japan ({type:entrez-nucleotide,attrs:{text:AB097089,term_id:40645273,term_text:AB097089}}AB097089, {type:entrez-nucleotide,attrs:{text:AB079782,term_id:32351753,term_text:AB079782}}AB079782, {type:entrez-nucleotide,attrs:{text:AB097090,term_id:40645275,term_text:AB097090}}AB097090); China ({type:entrez-nucleotide,attrs:{text:AJ311371,term_id:29134762,term_text:AJ311371}}AJ311371) and Taiwan ({type:entrez-nucleotide,attrs:{text:AM884180,term_id:198446713,term_text:AM884180}}AM884180). It also showed 86 % sequence identities with strains of BYMV: M11 ({type:entrez-nucleotide,attrs:{text:AB079886,term_id:109638255,term_text:AB079886}}AB079886) and IbG ({type:entrez-nucleotide,attrs:{text:AB079887,term_id:109638257,term_text:AB079887}}AB079887) from Japan and Vanilla ({type:entrez-nucleotide,attrs:{text:AY845011,term_id:61740434,term_text:AY845011}}AY845011, {type:entrez-nucleotide,attrs:{text:AY845012,term_id:61740436,term_text:AY845012}}AY845012) from India. The sequence identity of isolate-2 ({type:entrez-nucleotide,attrs:{text:JN692500,term_id:779787813,term_text:JN692500}}JN692500) was highest 86 % with isolates-1 ({type:entrez-nucleotide,attrs:{text:JF798580,term_id:341650451,term_text:JF798580}}JF798580) and 85–84 % with BYMV strains ({type:entrez-nucleotide,attrs:{text:AB079782,term_id:32351753,term_text:AB079782}}AB079782, {type:entrez-nucleotide,attrs:{text:AB097089,term_id:40645273,term_text:AB097089}}AB097089, {type:entrez-nucleotide,attrs:{text:AY845012,term_id:61740436,term_text:AY845012}}AY845012, {type:entrez-nucleotide,attrs:{text:AM884180,term_id:198446713,term_text:AM884180}}AM884180, {type:entrez-nucleotide,attrs:{text:AJ311371,term_id:29134762,term_text:AJ311371}}AJ311371, {type:entrez-nucleotide,attrs:{text:AY845011,term_id:61740434,term_text:AY845011}}AY845011, {type:entrez-nucleotide,attrs:{text:AB097090,term_id:40645275,term_text:AB097090}}AB097090, {type:entrez-nucleotide,attrs:{text:AB079886,term_id:109638255,term_text:AB079886}}AB079886, {type:entrez-nucleotide,attrs:{text:AB079887,term_id:109638257,term_text:AB079887}}AB079887). The 86–87 % sequence identities of isolates under study with other BYMV strains reported all over the world and in accordance with the species demarcation criteria and identification guidelines for potyviruses [1] suggested the virus isolates of V. faba under study as two isolates of BYMV. Phylogenetic analysis of nucleotide sequence of the BYMV isolates-1 and 2 of V. faba ({type:entrez-nucleotide,attrs:{text:JF798580,term_id:341650451,term_text:JF798580}}JF798580 and {type:entrez-nucleotide,attrs:{text:JN692500,term_id:779787813,term_text:JN692500}}JN692500) with the various BYMV strains of V. faba and other host species reported all over the world was performed using MEGA 4.0 tool. The BYMV strains clustered into two clusters, where the isolates under study clustered in cluster 1 along with Indian BYMV strains of Vanilla fragrans ({type:entrez-nucleotide,attrs:{text:AY845011,term_id:61740434,term_text:AY845011}}AY845011, {type:entrez-nucleotide,attrs:{text:AY845012,term_id:61740436,term_text:AY845012}}AY845012). The analysis of the BYMV isolate-1 ({type:entrez-nucleotide,attrs:{text:JF798580,term_id:341650451,term_text:JF798580}}JF798580) and isolate-2 ({type:entrez-nucleotide,attrs:{text:JN692500,term_id:779787813,term_text:JN692500}}JN692500) also revealed closest relationships with BYMV strains of Gentiana scabra ({type:entrez-nucleotide,attrs:{text:AB097089,term_id:40645273,term_text:AB097089}}AB097089, {type:entrez-nucleotide,attrs:{text:AB079782,term_id:32351753,term_text:AB079782}}AB079782, {type:entrez-nucleotide,attrs:{text:AB097090,term_id:40645275,term_text:AB097090}}AB097090) from Japan; close relationships with BYMV strains of G. scabra ({type:entrez-nucleotide,attrs:{text:AB079886,term_id:109638255,term_text:AB079886}}AB079886, {type:entrez-nucleotide,attrs:{text:AB079887,term_id:109638257,term_text:AB079887}}AB079887) from Japan, Eustoma russellianum ({type:entrez-nucleotide,attrs:{text:AM884180,term_id:198446713,term_text:AM884180}}AM884180) from Taiwan, {type:entrez-nucleotide,attrs:{text:AJ311371,term_id:29134762,term_text:AJ311371}}AJ311371 from China, V. fragrans ({type:entrez-nucleotide,attrs:{text:AY845011,term_id:61740434,term_text:AY845011}}AY845011, {type:entrez-nucleotide,attrs:{text:AY845012,term_id:61740436,term_text:AY845012}}AY845012) from India and distinct relationship with other BYMV strains of V. faba reported from Australia and Japan (Fig. 1b). Based on nucleotide sequence identities and phylogenetic relationships of the virus isolates of V. faba with various strains of BYMV, the virus isolates of V. faba under study were identified as two BYMV isolates. These isolates did not differ in symptoms on V. faba plant. The occurrence of BYMV on gladiolus in India [5], Japan [6], V. fragrans in India [2], V. faba in Australia [3], Egypt [7] and Iran [8] were reported previously. However, to our knowledge this is the first report of the natural occurrence of BYMV on V. faba in India.

Occurrence and coat protein sequence-based characterisation of Bean yellow mosaic virus (BYMV) associated with vanilla (Vanilla planifolia Andrews) in India

Thirty vanilla plants showing virus-like symptoms were subjected to reverse transcription-polymerase chain reaction (RT-PCR) using Bean yellow mosaic virus (BYMV) specific primers. The plants showing severe yellow mosaic and leaf distortion collected from Madikeri, Karnataka were found to be infected with BYMV. In RT-PCR, the BYMV specific primers amplified a ∼ 950 bp expected product that was cloned and sequenced. The sequenced region contained 957 bases spanning nuclear inclusion b (NIb) and coat protein (CP) genes. Sequence analyses and phylogenetic studies based on the CP region confirmed the identity of the virus as a strain of BYMV. This is the first report on the occurrence of BYMV infecting vanilla in India.

Identification strains of Bean Yellow Virus potyvirus (BYMV) on bean Phaseolus vulgaris in Iraq

everal methods were used to identify the virus, such as indicator plants, physical properties, manners transmission by aphids and ELISA test and among indicator plants two strains of BYMV were identified. The first one was showed a necrotic local lesion on bean while the second one was showed strong epinasty, veinal necrosis in inoculated leaves then it caused top necrosis at last severe systemic mottle. This two different symptoms gives a positive reaction at ELISA test and this test was indicated that the two symptoms is belong for two strains of bean yellow mosaic virus ( BYMV).The physical properties for the first strain about the Thermal Inactivating point (TIP) was 50-55ْc while the second strain was 60ْc and the dilution end point (DEP)for the first strain was 10-2 but it was 10-2 -10-3 for the second one and the longevity in vitro (LIV) for the first strain 48 hrs at room temperature and the main transmission by insect was achieved by several species of aphids.The double immunodiffution test in agar have been showed meeting of two precipitin line without cross in this two lines when used antiserum of the first strain of virus against the two sap of infected plants with both strains of virus and this test was used in the second strain against sap of the both infected plants too with the two strains of the virus and this test was additional indication that the two symptoms in bean were belonged to a two different strains to the same virus.

The same allele of translation initiation factor 4E mediates resistance against two Potyvirus spp. in Pisum sativum.

Pathogenicity of two sequenced isolates of Bean yellow mosaic virus (BYMV) was established on genotypes of Pisum sativum L. reported to carry resistance genes to BYMV and other potyviruses. Resistance to the white lupin strain of BYMV (BYMV-W) is inherited as a recessive gene named wlv that maps to linkage group VI together with other Potyvirus resistances. One of these, sbm1, confers resistance to strains of Pea seedborne mosaic virus and previously has been identified as a mutant allele of the eukaryotic translation initiation factor 4E gene (eIF4E). Sequence comparison of eIF4E from BYMV-W-susceptible and -resistant P. sativum genotypes revealed a polymorphism correlating with the resistance profile. Expression of eIF4E from susceptible plants in resistant plants facilitated BYMV-W infection in inoculated leaves. When cDNA of BYMV-W was agroinoculated, resistance mediated by the wlv gene frequently was overcome, and virus from these plants had a codon change causing an Arg to His change at position 116 of the predicted viral genome-linked protein (VPg). Accordingly, plants carrying the wlv resistance gene were infected upon inoculation with BYMV-W derived from cDNA with a His codon at position 116 of the VPg coding region. These results suggested that VPg determined pathogenicity on plants carrying the wlv resistance gene and that wlv corresponded to the sbm1 allele of eIF4E.

First Report of Bean yellow mosaic virus (Pea Mosaic Strain) in Verbena × hybrida.

Verbena × hybrida is an ornamental annual used in rock gardens as an edging plant and hanging baskets. It comes in a variety of colors and grows approximately 1.5 to 2.5 cm (6 to 10 inches) high. In the spring of 2002, verbena cv. Lavender Shades plants from California showing leaf mosaic symptoms tested positive for potyvirus using an antigen-coated plate enzyme-linked immunosorbent assay with our genus Potyvirus broad spectrum reacting PTY-1 monoclonal as the detecting antibody (3). The virus was transmitted mechanically to Nicotiana benthamiana by sap inoculation from infected verbena plants. Infected tobacco showed systemic mild mosaic symptoms. Total RNA extractions from infected verbena and tobacco leaves were used in reverse transcription-polymerase chain reaction (RT-PCR) assays with generic potyvirus-specific primers that amplify highly conserved 700-bp or 1,600-bp fragments from the 3' terminus of most potyviruses. This region includes the 3' noncoding region (3'NCR) and the potyviral coat protein (CP). The PCR-amplified fragments were cloned by using standard TA cloning procedures and sequenced using dye-terminator chemistry. The cloned nucleotide and putative coat protein amino acid sequences from the infected verbena and tobacco plants were compared with the corresponding regions of other potyviruses. Amino acid comparison of the CP region of the verbena po-tyvirus showed 95 to 96% identity to four pea mosaic strains (PMV) of Bean yellow mosaic virus (BYMV), 85 to 89% identity to 20 other strains of BYMV, 74 to 76% identity with six strains of Clover yellow vein virus (CYVV), and only 50 to 64% identity with 28 other potyviruses. Pairwise comparisons among and between the CP sequences of PMV, BYMV, CYVV, and other potyviruses revealed identities of 92 to 99% for BYMV∷ BYMV, PMV∷PMV, and CYVV∷CYVV; 84 to 89% for BYMV∷ PMV, 69 to 78% for BYMV∷CYVV and PMV∷CYVV, and 50 to 64% for all other potyvirus combinations. Additionally, similar pairwise analysis of the 3'NCR of the verbena potyvirus revealed 98 to 99% identity to PMV strains, 81 to 94% to other BYMVs, 68 to 75% to CYVVs, and 52 to 64% with other potyviruses. Other 3'NCR pairwise comparisons generally revealed the same identity trend as described for the CP. Further serological analysis with our panel of BYMV-specific, BYMV-subgroup, and potyvirus cross-reactive monoclonal antibodies (3) confirmed the designation of the verbena potyvirus isolate as a pea mosaic strain of BYMV. To our knowledge this is the first confirmed report of BYMV-pea mosaic strain in Verbena (1,2).

Yield limiting potential of necrotic and non-necrotic strains of Bean yellow mosaic virus in narrow-leafed lupin (Lupinus angustifolius)

The yield losses caused by necrotic and non-necrotic strains of Bean yellow mosaic virus (BYMV) in narrow-leafed lupin (Lupinus angustifolius) were quantified in field experiments. Clover plants infected with either were introduced into plots to provide infection sources, and aphids spread infection to the lupin plants. When the effects of virus infection were examined in individual lupin plants infected with necrotic BYMV, they were killed by early infection so there was no seed production. With late infection, shoot dry wt, seed yield, and seed number were decreased by at least 55%, 80%, and 74%, respectively. With non-necrotic BYMV, shoot dry wt, seed yield, and seed number diminished with increasing duration of plant infection, these decreases ranging over 27–88%, 48–99%, and 35–98% for late to early infection, respectively. In partially infected stands in which both necrotic and non-necrotic BYMV were spreading, an additional incidence of 28% in plots with introduced non-necrotic strain foci over that in plots without introduced foci was sufficient to decrease overall seed yield significantly. However, an additional incidence of 10% was insufficient to do so in plots with introduced necrotic strain foci. In plots into which different numbers of clover plants infected with non-necrotic BYMV were introduced, subsequent incidence of infection depended on the magnitude of the initial virus source, and yield was decreased by 21–24%, 31–43%, and 64–66% with 4, 8, or 16 foci/plot, respectively. With both types of strain, yield loss in infected plants was mainly due to failure to produce any seed or to fewer seeds being produced, but smaller seed size also contributed. These results show that non-necrotic strains of BYMV have considerable yield-limiting potential in narrow-leafed lupin crops despite causing milder symptoms than necrotic strains. No evidence was obtained of seed-transmission of non-necrotic BYMV in narrow-leafed lupin, but a 0.2% seed transmission rate was detected in yellow lupin (Lupinus luteus).

Distribution and incidence of necrotic and non-necrotic strains of bean yellow mosaic virus in wild and crop lupins

A new strain of bean yellow mosaic virus (BYMV), a non-necrotic strain, was found in south-west Western Australia. It differs from the original necrotic strain of BYMV in that it does not kill Lupinus angustifolius (narrow-leafed lupin) plants, but causes symptoms of mottle and stunting, or dead growing points, fleshy expanded leaves, and stunting. A survey of L. angustifolius crops during September and October 1997 compared the distribution and incidence of the necrotic strain with that of the non-necrotic strain. Based on 1000 plants inspected at the edge of each crop, the necrotic strain was found in 100 of 102 crops while the non-necrotic strain was found in 64 of them. Incidences ranged from 0.3 to 56% (necrotic strain) and 0.1 to 7% (non-necrotic strain) of plants counted. Both strains were present over the whole range of the survey. Wild L. angustifolius and L. luteus (yellow lupin) populations were also inspected. The necrotic and non-necrotic strains were found in 31 and 9 of the 34 L. angustifolius populations examined, respectively. Incidences ranged from 0.1 to 28% (necrotic strain) and 0.1 to 3% (non-necrotic strain) of plants counted. BYMV was found in 9 of 11 wild L. luteus populations with incidences ranging from 0.3 to 7% of plants counted. In a separate survey in which samples of L. angustifolius crops, with necrotic symptoms suspected of being caused by Colletotrichum gloeosporioides (lupin anthracnose disease), were examined, 37 of 130 samples had typical necrotic BYMV symptoms. Samples with these necrotic symptoms also came from northern and eastern wheatbelt areas not normally associated with BYMV infection. When 8 BYMV isolates cultured by sap inoculation in Trifolium subterraneum (subterranean clover) were tested by aphid transmission to L. angustifolius plants in 1994 and again in 1997, the isolates of the 2 strains behaved the same on both occasions causing only necrotic (3 isolates) or non-necrotic (5 isolates) symptoms. Thus, despite repeated subculture by sap inoculation over a 3.5-year period, the 2 BYMV strains still remained distinct. An isolate collected from wild L. luteus in 1997 produced only non-necrotic symptoms in L. angustifolius. The non-necrotic strain caused symptoms typical of BYMV in hosts other than L. angustifolius, reacted strongly with BYMV antiserum, and failed to react with antiserum to clover yellow vein virus. In a BYMV-infected lupin crop, grain yields of individual L. angustifolius plants infected early with the non-necrotic strain were decreased by 95%. Shoot weights, seed number, and seed size were also greatly decreased. Widespread occurrence of the non-necrotic strain of BYMV is cause for concern for the lupin industry.

Nucleotide sequence of the 3'-terminal region of the genome confirms that pea mosaic virus is a strain of bean yellow mosaic potyvirus.

The 1,035 nucleotides at the 3'end of the I strain of pea mosaic potyvirus (PMV-I) genomic RNA, encoding the coat protein, have been cloned and sequenced. A comparison of the derived coat protein sequence with those of the bean yellow mosaic virus (BYMV) strains, CS, S, D and GDD, indicates that PMV-I is a strain of BYMV. Sequence comparisons and hybridisation studies using the 3'-noncoding region support this classification. The nucleotide and protein sequence data also suggest that PMV-I and BYMV-CS form one subset of BYMV strains while the other three strains form another.

Sequence Relationships Among the Coat Proteins of Strains of Pea Mosaic, White Lupin Mosaic, and Bean Yellow Mosaic Potyviruses

The taxonomic relationships of 20 potyvirus isolates from the bean yellow mosaic virus (BYMV) subgroup were investigated by high-performance liquid chromatographic peptide profiling of tryptic digests of their coat proteins. The peptide profiles of the clover yellow vein virus (CIYVV) strains B, C81, LI, and Washington were almost identical to each other and were closely related to that of CIYVV-Pratt, confirming their status as strains of CIYVV and not strains of BYMV. The profiles of BYMV-GDD, G, WA8, WA22, and RL7 were almost superimposable on each other and were similar to the profiles of BYMV-Scott, S, G81, and F, indicating that their coat proteins were very similar []

Three strains of bean yellow mosaic virus: symptoms and accumulation in eight pea cultivars (Pisum sativum L.)

A pea mosaic strain and a bean strain of bean yellow mosaic virus (BYMV) were isolated from naturally infected pea and broad bean plants and named BYMV-Ps and BYMV-Vf, respectively. A third strain of BYMV isolated from Gladiolus (BYMV-G) was obtained from Denmark which was distinguished from the two above strains serologically and by its symptoms in test plants. BYMV-Ps and BYMV-Vf caused yellow mosaic symptoms and green mosaic symptoms, respectively, in eight pea cultivars tested, but the concentration of BYMV varied among the cultivars. BYMV-G caused mild mosaic or vein clearing in peas. A need to improve resistance to BYMV in the Finnish pea varieties was recognized.

Inheritance and Backcross Breeding of the Hypersensitive Reaction to Bean Yellow Mosaic Virus in Red Clover1

Bean yellow mosaic virus (BYMV) is an important pathogen of red clover (Trifolium pratense L.). A hypersensitive reaction to the most prevalent strain of BYMV in Kentucky (designated 204‐1) conveys resistance. The objectives of the present study were to backcross the genes for the hypersensitive reaction into 10 clones of ‘Kenstar’ to widen the BYMV resistance of this cultivar and to further investigate the inheritance of resistance. Populations of Fl’s and five backcrosses to each of the 10 parental clones of Kenstar were produced using the clones as recurrent parents and a hypersensitive reacting clone as the nonrecurrent parent. Four Kenstar parental clones were found to possess the hypersensitive reaction, and two had a different type of resistance. Inheritance of the hypersensitive reaction to BYMV strain 204‐1 was similar to that reported earlier. Incorporation of the hypersensitive reaction to strain 204‐1 into the Kenstar clones did not increase virus resistance under spaced‐plant field conditions as compared to Kenstar polycross progenies. Lack of infection in broadcast plots prevented a complete assessment of the potential effect of the hypersensitive reaction. A new strain of BYMV was discovered and designated the red clover or ‘RC’ strain. This strain is similar to previously described isolates of BYMV from soybean, and it was hypothesized that the RC strain may have occurred as a result of the increase in soybean acreage in Kentucky. Phenotypic recurrent selection under spaced‐plant conditions where opportunity exists for infection by many different strains of BYMV and other viruses is suggested as aneffective breeding procedure.

Towards a system for the identification and classification of potyviruses: II. Virus particle length, symptomatology, and cytopathology of six distinct viruses

The mean particle lengths of lettuce mosaic virus (LMV), bean common mosaic virus (BCMV), passionfruit woodiness virus (PWV), potato virus Y (PVY), sugarcane mosaic virus (SCMV), and one strain of bean yellow mosaic virus (BYMV) were all shown to be close to 750 nm. However, the length of two other serologically closely related strains of BYMV, variants of pea mosaic virus referred to as PMV and SPMV, had significantly longer particles, about 792 and 842 nm. Each of the distinct viruses had readily distinguishable host ranges. The strains of BYMV could also be distinguished from each other although they had many hosts in common with similar symptoms. Electron microscopy of plant cells infected by the viruses studied showed that the cell inclusions induced by infection were of two readily distinguishable types although some minor virus-specific differences were also observed. The BYMV strains and LMV induced long “relaxed” pinwheel inclusions whereas those induced by BCMV, PWV, PVY, and SCMV were shorter, “tighter,” and curved. The significance of these observations to problems of potyvirus identification and classification is discussed.

Serologically and Biologically Distinct Bean Yellow Mosaic Virus Strains

Serologically and Biologically Distinct Bean Yellow Mosaic Virus Strains

Purification and serology of bean yellow mosaic virus.

Isolate No.30 of bean yellow mosaic virus (BYMV) was purified from broad bean leaves by extraction with 0.1M Tris-HCl buffer, pH7.0, containing 0.05M EDTA and 1% 2-mercaptoethanol; repeated clarification with carbon tetrachloride and precipitation with 4% polyethylene glycol (#6, 000) followed by differential centrifugation and sucrose density-gradient centrifugation. ISCO fractionator scanning patterns indicated a high degree of purity but serological results revealed the presence of some host contaminates. The yield of virus was about 2mg/100g of broad bean leaves.The titer of the antiserum against isolate No.30 was 1/2048 by ring precipitin tests. Although the intact virus particles could not diffuse in agar gel plates, a clear precipitin line was observed when 0.5% SDS (or LIS) was added to the agar or virus suspension. Isolate No.30 was compared serologically with a necrotic strain and a chlorotic spot strain of BYMV in agar gel diffusion tests. Spur reactions were observed between isolate No.30 and these strains.

Differential Aphid Transmission of Two Bean Yellow Mosaic Virus Strains and Comparative Transmission by Biotypes and Stages of the Pea Aphid1, 2

Two strains of bean yellow mosaic virus (BYMV) were compared as to (1) transmissibility by Acyrthosiphon pisum (Harris) and Myzus persicae (Sulzer) (Homoptera: Aphididae) and (2) effects on selected herbaceous host plants. A strain from Michigan (Mich BYMV) was not transmissible by A. pisum in 1200 trials with single aphids even though various instars of 2 biotypes, 1 to 15-minute acquisition-probing periods, 2 source plant species, and various probing sites were used. M. persicae adults did not transmit Mich BYMV in 88 trials; nymphs were not tested. A strain from Oregon (Ore IV BYMV) was transmitted with about 50% efficiency by 1st instars of A. pisum (Biotype EL) and by adult M. pcrsicac following 1 to 10-minute acquisition-probing periods. Three A. pisum biotypes (EL, EL, and WARF) that were isolated on the basis of their efficiency (EL and EL1: efficient; WARF: inefficient) in transmitting peaenation mosaic virus (PEMV) were compared as vectors of Ore IV BYMV. Adults of El1 and WARF were unable to transmit virus whereas adults of EL were 29.0 and 19.8% efficient after 1- and 5-minute acquisition-probing periods, respectively. Maximum transmission by 1st instars after either probing period was: EL 49.5%, EL, 7.6%, and WARF 15.2%. Thus, Biotypes EL and WARF have transmitted both a circulative virus (PEMV) and a stylet-borne virus (BYMV) with the same relative transmission efficiency whereas EL1 was an efficient vector of PEMV and a poor vector of BYMV. First instars of Biotype EL transmitted Ore IV BYMV with significantly greater ( P = <0.05) efficiency after 1- and 5-minute acquisitionprobing periods than did adults. A differential host reaction occurred on Phascolus vulgaris L. when plants were mechanically inoculated with the 2 virus strains. Typical brilliant yellow mosaic symptoms were produced in response to Mich BYMV infection whereas only moderate chlorotic spotting was induced by Ore IV BYMV.