Bean Yellow Mosaic Virus Infection Research Articles

Physio-biochemical and nutritional alterations in faba bean due to bean yellow mosaic virus infection

Physio-biochemical and nutritional alterations in faba bean due to bean yellow mosaic virus infection

Enhancing systemic resistance in faba bean (Vicia faba L.) to Bean yellow mosaic virus via soil application and foliar spray of nitrogen-fixing Rhizobium leguminosarum bv. viciae strain 33504-Alex1.

Rhizobium spp. manifests strong nitrogen fixation ability in legumes. However, their significance as biocontrol agents and antivirals has rarely been investigated. Under greenhouse conditions, the molecularly identified nitrogen-fixing plant growth-promoting rhizobacteria (PGPR), Rhizobium leguminosarum bv. viciae strain 33504-Alex1, isolated from the root nodules of faba bean plants, was tested as a soil inoculum or a foliar application to trigger faba bean plants’ resistance against Bean yellow mosaic virus (BYMV) infection. Compared to the non-treated faba bean plants, the applications of 33504-Alex1 in either soil or foliar application significantly promoted growth and improved total chlorophyll content, resulting in a considerable reduction in disease incidence and severity and the inhibition index of BYMV in the treated faba bean plants. Furthermore, the protective activities of 33504-Alex1 were associated with significant reductions in non-enzymatic oxidative stress markers [hydrogen peroxide (H2O2) and malondialdehyde (MDA)] and remarkably increased DPPH free radical scavenging activity and total phenolic content compared to the BYMV treatment at 20 days post-inoculation. Additionally, an increase in reactive oxygen species scavenging enzymes [superoxide dismutase (SOD) and polyphenol oxidase (PPO)] and induced transcriptional levels of pathogenesis-related (PR) proteins (PR-1, PR-3, and PR-5) were observed. Of the 19 polyphenolic compounds detected in faba bean leaves by high-performance liquid chromatography (HPLC) analysis, gallic and vanillic acids were completely shut down in BYMV treatment. Interestingly, the 33504-Alex1 treatments were associated with the induction and accumulation of the most detected polyphenolic compounds. Gas chromatography-mass spectrometry (GC-MS) analysis showed hexadecanoic acid 2,3-dihydroxypropyl ester, tetraneurin-A-Diol, oleic acid, and isochiapin B are the major compounds in the ethyl acetate extract of 33504-Alex1 culture filtrate (CF), suggesting it acts as an elicitor for the induction of systemic acquired resistance (SAR) in faba bean plants. Consequently, the capacity of R. leguminosarum bv. viciae strain 33504-Alex1 to enhance plant growth and induce systemic resistance to BYMV infection will support the incorporation of 33504-Alex1 as a fertilizer and biocontrol agent and offer a new strategy for crop protection, sustainability, and environmental safety in agriculture production.

Act of Malondialdehyde and Total Phenolic Content Under Bean Yellow Mosaic Virus Infection and Biostimulants Application

Bean yellow mosaic virus represents a stress effect on fava bean plants. This study was conducted to assess the lipid peroxidation and total phenolic content (TPC) of fava bean plants under bean yellow mosaic virus infection and its management by the biostimulants; Rhizobium and Bacillus species spraying application. The obtained data revealed that virus-infected plants maximized stress factors, the content of malondialdehyde (MDA), while it decreased in other applications. TPC significantly increased in Bacillus, and Rhizobium isolates spraying treatments with 20.99 and 22.44 mg/100g extract, respectively, compared with control. The current work provides bio-resistance by Bacillus or Rhizobium isolates effectively minimizes the adverse effects of challenges such as stressing viral infection and representing an environmentally friendly commercial value for plant growers.

Mitigating effects of Bean yellow mosaic virus infection in faba bean using new carboxymethyl chitosan-titania nanobiocomposites

Bean yellow mosaic virus (BYMV) is the main cause of the mosaic and malformation of many plants, worldwide. Thus, the triggering of plant systemic resistance against BYMV is of great interest. In this endeavor, we aimed to explore the capacity of new carboxymethyl chitosan-titania nanobiocomposites (NBCs, NBC1,2) to trigger faba bean plants resistance against BYMV. Effects of NBCs on faba bean (Vicia faba L.) disease severity (DS), growth parameters, and antioxidant defense system activity were investigated under BYMV stress. Noticeably that the DS in NBCs-treated faba bean was significantly reduced compared to untreated plants. Moreover, treatment with NBCs was remarkably increased growth indices, photosynthetic pigments, membrane stability index, and relative water content compared to challenge control. Additionally, enzymatic and non-enzymatic antioxidants and total soluble protein were significantly increased. Contrary, electrolyte leakage, hydrogen peroxide, and lipid peroxidation were reduced. Interestingly that NBC1 has higher efficacy than NBC2 in triggering plant immune-system against BYMV as indicated from DS percentage (DS = 10.66% and 19.33% in case of plants treated with NBC1 and NBC2, respectively). This could be attributed to the higher content of TNPs in NBC1 (21.58%) as compared to NBC2 (14.32%). Overall, NBCs offer safe and economic antiviral agents against BYMV.

Molecular Assessment of Ten Faba Bean Genotypes Dissimilar in Bean Yellow Mosaic Virus Susceptibility

The point of this investigation was to decide the hereditary inconstancy and break down the connection between four faba bean cultivars and six promising lines utilizing inter simple sequence repeats (ISSR) markers. Faba bean genotypes were gathered by their resistance to the bean yellow mosaic virus infection. With the acquired band registration, a paired data matrix was built to perform the comparing statistical analysis. The used ISSR markers created 148 fixed and repeatable bands, of which 75 were polymorphic. The values of resolution power (Rp), polymorphic information content (PIC), and marker index (MI), uncovered that primer ISSR-14 was the most effective to break down hereditary changeability with estimations of 5.8, 0.80, and 6.40, respectively, followed by primers ISSR-6 and ISSR-18. Genetic distances swayed somewhere in the range of 0.78 and 0.91, and checked the groupings saw in the dendrogram, which demonstrates high change at the degree of DNA among the investigated genotypes, watching six characterized gatherings as indicated by UPGMA examination. In the examination of fundamental segments, the enrolled groupings were dictated by the source of the origin of the gathering. The utilization of ISSR markers was effective to describe at the degree of DNA the evaluated bean genotypes, showing the presence of inconstancy, the recognized differentiating promotions can be used in hereditary improvement projects planned for settling the requirements of the producers.

Elimination of Bean yellow mosaic virus from infected cormels of three cultivars of gladiolus using thermo-, electro- and chemotherapy.

Bean yellow mosaic virus (BYMV) is a prevalent virus and major threat to gladiolus cultivation the world over. In the gladiolus repository at CSIR-NBRI, Lucknow, several plants (82-88%) of three economically important cultivars were found infected by BYMV showing severe mosaic and stripe symptoms. Affected plants exhibit diminished quality and quantity of florets and corms, thus reducing their value. Attempts were made to eliminate BYMV from the infected gladiolus cormel explants in vitro through thermotherapy (37°C for 30days), chemotherapy (30mg/L ribavirin for 30days), and electrotherapy (30mA for 20min), either alone and in different combinations. The in vitro regenerated plants were free from BYMV infection when checked by RT-PCR using BYMV-specific primers. The combination of electro- and chemotherapies has given the best response as compared to other treatments. Among the individual therapies, electrotherapy (30mA/20min) was found to be the best for and production of BYMV-free gladiolus plants (44-46%) with moderate regeneration efficiency (54-58%) followed by chemotherapy and thermotherapy. However, the cormels obtained from a combination of electro- and chemotherapy treatment (30mA/20min + 30mg/L) has given highest virus free (46-52%) and highest therapy efficiency indices (56%) as compared to other treatments. Further, these cormels showed better developed root systems and produced more cormels which were larger in size as compared to the other treatments and control when grown in tissue culture media.

First Report of Bean Yellow Mosaic Virus Infecting Nasturtium (Tropaeolum majus) in Hawaii

Garden nasturtium (Tropaeolum majus L.) is an herbaceous annual plant commonly used as a garden ornamental, culinary herb, or a medicinal plant. It has become naturalized in many locations and is currently considered an alien invader in New Zealand, Lord Howe Island, and Hawaii (U.S. Forest Service 2012). Bean yellow mosaic virus (BYMV) is an aphid-transmitted nonpersistent potyvirus with a wide host range (Parrella and Lanave 2009). In February 2018, we observed nasturtium plants exhibiting severe chlorotic mosaic symptoms at the Kula Botanical Gardens on Maui, HI (20°44′40.01″ N, 156°19′03.00″ W). We tested six samples that had severe yellow mosaic and leaf distortion symptoms and three leaves from nonsymptomatic plants using potyvirus-specific ELISA (Agdia, Elkhart, IN) and universal potyvirus-specific reverse transcription polymerase chain reaction (RT-PCR) with potyvirus nuclear inclusion body (NIb) primers NIb2F and NIb3R (Zheng et al. 2010). All of the symptomatic nasturtium samples tested positive for potyvirus infection in both tests, whereas three nonsymptomatic nasturtium leaves tested negative in both tests. To identify the specific potyvirus involved, amplicons (309 bp) of the NIb region that were generated by RT-PCR using universal potyvirus-specific primers were sequenced (accession MH422546). BLASTn analysis of the sequences showed that this virus shared 93% nucleotide identity with a BYMV isolate from Australia (HG970862), and BLASTx analysis showed it shared 93% amino acid identity with a polyprotein of BYMV isolate from Australia (CDO67686). Two additional sets of PCR primers were used to further characterize the isolate: BYMV NIb-specific primers BYMV-NIb-3 (5′-CCACTGTTATTCCCTTTAAAC-3′) and BYMV-NIb-5 (5′-AATAAGTTCTACAGTTTGCACC-3′), and BYMV coat protein (CP)-specific primers BYMV-CP-3 and BYMV-CP-5 (Wang et al. 2017). BLASTn analysis of the 257-bp NIb amplicon (accession MH422547) shared 94% identity to an Australian isolate of BYMV (HG970847), and the 595-bp CP amplicon (accession MH422548) shared 98% identity to another Australian isolate of BYMV (HG970860). BLASTx analysis of the 257-bp NIb amplicon shared 93% identity to an Australian isolate polyprotein of BYMV (AHQ95554), and the 595-bp CP amplicon shared 98% identity to another Japan isolate polyprotein of BYMV (BAA93683). All six symptomatic samples also tested positive for BYMV by triple-antibody sandwich ELISA using a BYMV-specific antibody (DSMZ, Braunschweig, Germany). From March to June 2018, 24 additional nasturtium samples were collected from two different locations on Maui, and all tested positive for BYMV infection by RT-PCR and ELISA. All of the symptomatic nasturtium samples tested positive for BYMV infection in both tests, while three nonsymptomatic nasturtium leaves from other plants tested negative in both tests. To our knowledge, this is the first report of BYMV infecting nasturtium plants in Hawaii. Nasturtium is a widely grown herbaceous ornamental in Hawaii. It could be harboring BYMV in the off-season and moving it to cultivated legume plants. Therefore, further study is needed to determine whether legume aphids can transmit BYMV from nasturtium to healthy legume plants. In addition, further studies on the distribution of BYMV-infected nasturtium and identification of other BYMV-infected plants in the Hawaiian Islands are needed.

Induction of Systemic Resistance to Bean yellow mosaic virus (BYMV) Infecting Bean Plants Using Plant Extracts and Salicylic Acid

Bean yellow mosaic virus (BYMV) was appeared to be in the last years the most frequently destructive virus of bean crop causing mosaic with bright yellowing symptoms. The virus was isolated in different locations in Egypt, and detected by using DAS-ELISA and Dot-blot immunobinding assay (DBIA). Initiative or introductory screening of inducers against BYMV infection on bean plants directed by using the local lesion assay (LLA) Chenopodium amaranticolor L. All used inducers were effective in decreasing the local lesion formation by the virus inoculation. Biochemical and ultrastructural modifications of bean plants (Phaseolus vulgaris, L. cv. karnk) leaves in response to Systemic Acquired Resistance (SAR) to BYMV infection. Treating of all inducers on infected bean leaves were effective in banning or obstruction of destroying and smashing effects that resulted after virus infection. ELISA was used as a diagnostic tool at the end to SAR. Extract of Dianthus caryophyllus L. was the most effective against BYMV as a factor of resistance induction.

Apple latent spherical virus vector as vaccine for the prevention and treatment of mosaic diseases in pea, broad bean, and eustoma plants by bean yellow mosaic virus.

We investigated the protective effects of a viral vector based on an Apple latent spherical virus (ALSV) harboring a segment of the Bean yellow mosaic virus (BYMV) genome against mosaic diseases in pea, broad bean, and eustoma plants caused by BYMV infection. In pea plants pre-inoculated with the ALSV vaccine and challenge inoculated with BYMV expressing green fluorescence protein, BYMV multiplication occurred in inoculated leaves, but was markedly inhibited in the upper leaves. No mosaic symptoms due to BYMV infection were observed in the challenged plants pre-inoculated with the ALSV vaccine. Simultaneous inoculation with the ALSV vaccine and BYMV also prevented mosaic symptoms in broad bean and eustoma plants, and BYMV accumulation was strongly inhibited in the upper leaves of plants treated with the ALSV vaccine. Pea and eustoma plants were pre-inoculated with BYMV followed by inoculation with the ALSV vaccine to investigate the curative effects of the ALSV vaccine. In both plant species, recovery from mosaic symptoms was observed in upper leaves and BYMV accumulation was inhibited in leaves developing post-ALSV vaccination. These results show that ALSV vaccination not only prevents mosaic diseases in pea, broad bean, and eustoma, but that it is also effective in curing these diseases.

Black Pod Syndrome ofLupinus angustifoliusIs Caused by Late Infection withBean yellow mosaic virus

Black pod syndrome (BPS) causes devastating losses in Lupinus angustifolius (narrow-leafed lupin) crops in Australia, and infection with Bean yellow mosaic virus (BYMV) was suggested as a possible cause. In 2011, an end-of-growing-season survey in which L. angustifolius plants with BPS were collected from six locations in southwestern Australia was done. Tissue samples from different positions on each of these symptomatic plants were tested for BYMV and generic potyvirus by enzyme-linked immunosorbent assay and reverse-transcription polymerase chain reaction (RT-PCR). Detection was most reliable when RT-PCR with generic potyvirus primers was used on tissue taken from the main stem of the plant just below the black pods. Partial coat protein nucleotide sequences from eight isolates from BPS-symptomatic L. angustifolius plants all belonged to the BYMV general phylogenetic group. An initial glasshouse experiment revealed that mechanical inoculation of L. angustifolius plants with BYMV after pods had formed caused pods to turn black. This did not occur when the plants were inoculated before this growth stage (at first flowering) because BYMV infection caused plant death. A subsequent experiment in which plants were inoculated at eight different growth stages confirmed that BPS was only induced when L. angustifolius plants were inoculated after first flowering, when pods had formed. Thus, BYMV was isolated from symptomatic L. angustifolius survey samples, inoculated to and maintained in culture hosts, inoculated to healthy L. angustifolius test plants inducing BPS, and then successfully reisolated from them. As such, Koch's postulates were fulfilled for the hypothesis that late infection with BYMV causes BPS in L. angustifolius plants.

Evaluation of the Czech core collection of Trifolium pratense, including morphological, molecular and phytopathological data

The Czech national core collection of the red clover (Trifolium pratense L.) was established in 2006 based on previous analyses (2004 to 2005) of morphological and some phytopathological data observed in the field conditions. Input set included 57 tetraploid accessions (varieties and newly bred varieties) and 130 diploid accessions (varieties, newly bred varieties and wild forms collected from nature) of the world collection. The core collection includes 76 accessions. Molecular and phytopathological data on the core collection were obtained after its establishment during 2007. The core collection was from the point of view of resistance to important fungal and viral pathogens evaluated. Tested plants were inoculated by spore-suspension of Fusarium sp. fungi and also by Bean yellow mosaic virus (BYMV). Microsatellites (SSRs) were used for the study of genetic diversity of all the core collections accessions. No clear difference between diploid and tetraploid accessions within the core collection was evidenced by cluster analysis of morphological data. Notable correlation was found only between the seed weight and ploidy level. The relationships among accessions were analysed with hierarchical clustering, separately for the morphological data (50 characters) and the data on SSR polymorphism (11 primers, 23 polymorphic bands). Molecular and morphological data were not significantly correlated. No differences in particular morphological characters were observed to be associated with the presence/absence of particular bands or with the overall pattern of SSR polymorphism. Dendrogram of accessions included into the Czech core collection of the red clover based on morphological data showed separation of items into seven subclusters, while dendrogram based on molecular data showed the separation of items into 13 subclusters. The core collection accessions showed some level of resistance to Fusarium sp. and BYMV infection. The correlation between resistance of core collection accessions to Fusarium sp. and BYMV pathogens was not significant. Key words: Red clover, core collection, genetic diversity, ploidy level, microsatellites, morphological characteristics, Fusarium sp., BYMV.

Parasitoids aid dispersal of a nonpersistently transmitted plant virus by disturbing the aphid vector

1 Aphids are the major group of insects that vector plant viruses, and they often display a preference for foliage showing disease symptoms. Although this behaviour will increase the numbers of vectors acquiring the pathogen, it will not in itself result in a greater spread of the disease. 2 The present study examined how infection of Vicia faba by the nonpersistently transmitted virus bean yellow mosaic virus (BYMV) affected colonization by pea aphids Acyrthosiphon pisum. We then examined how foraging by the hymenopterous parasitoid Aphidius ervi affected aphid settling/movement behaviour and the consequences for dissemination of the virus. 3 In Petri dish arenas, aphids colonized discs from BYMV-infected leaves more rapidly than discs from uninfected plants. Reflectance from infected foliage was approximately 20% higher than from uninfected leaves in the green–yellow wavelengths, indicating that aphids might be responding to visual cues from the brighter foliage. Settling was reduced by A. ervi, with the foraging wasps preventing the aphids reaching and/or remaining on the leaf tissue. 4 In multiple plant arenas, A. ervi caused a reduction in aphid numbers but also a nine-fold increase in BYMV infection. It is hypothesized that disturbance by the parasitoids resulted in more aphid movement as well as more cases of aphids probing on a BYMV-infected plant and then a new host within the critical time period for successful inoculation to occur. This effect of parasitoids on virus dispersal should be considered in epidemiological models of insect-vectored plant diseases, and also when evaluating the use of natural enemies in biocontrol strategies of insect herbivore/vector pests.

Modifications of antioxidant activity and protein composition of bean leaf due to Bean yellow mosaic virus infection and salicylic acid treatments

The antioxidant status as well as protein composition of faba bean leaves infected with Bean yellow mosaic virus (BYMV) and the effect of salicylic acid application was examined in this paper. Some modifications in the antioxidant status were observed by changing some antioxidant enzymes activities and contents of antioxidant metabolites. BYMV-infected leaves revealed POD, CAT, APX and SOD induced activities while SA treatments could inhibit POD, CAT activities but induced SOD activity. The enzyme activities seemed to be SA concentration dependant. Higher H2O2 and MDA concentrations were recorded in virus-infected leaves than those of the corresponding controls while treatment with SA followed by virus inoculation caused lowering of MDA concentration and reducing the damage due to lipid peroxidation. Moreover, because of virus infection and/or SA treatments, an increase in the amounts of phenolics and flavonoids was noticed. As compared to the control, BYMV infection or SA application caused pronounced increase in the antioxidant activity of leaf extracts detected by DPPH assay, indicating an increase in the amounts of antioxidant compounds occurred. To test the protein composition, the contents of each protein fractions (soluble, insoluble and total) were analyzed and the change in protein patterns was visualized using SDS-PAGE. The BYMV-infected bean leaves had protein contents higher than the control indicating accumulation of pathogenesis-related proteins. Moreover, spraying SA with or without virus inoculation could accumulate soluble, insoluble and total proteins and the pattern of increase was in accordance with SA concentration. Alterations in protein patterns were observed in faba bean leaves (Vicia faba cv Giza 461) in response to BYMV infection and SA treatments. Because of BYMV infection and SA treatments, the protein profiles showed new bands in comparison to the control. Some polypeptides were highly accumulated in treatments of SA followed by virus inoculation. Changing antioxidant status and accumulation of some antioxidant metabolites as well as the pronounced alterations in the protein composition indicate a kind of plant response against pathogen invasion and in case of SA treatment it is considered a way by which a defence response was initiated and/or activated.

Protective action of salicylic acid against bean yellow mosaic virus infection in Vicia faba leaves

In this study, morphological, ultrastructural and physiological modifications of faba bean (Vicia faba cv Giza 461) leaves in response to bean yellow mosaic virus (BYMV) infection and salicylic acid (SA) treatments were examined. Under BYMV stress, leaves showed symptoms including severe mosaic, mottling, crinkling, size reduction and deformations. Three weeks after virus inoculation, photosynthetic rate, pigment contents and transpiration rate were significantly reduced in response to BYMV infection. Ultrastructural investigations of BYMV-infected leaves demonstrated that most chloroplasts with increased stromal area became spherical in shape and some lost their envelopes, either partially or totally. The internal structures of chloroplast, grana and thylakoids were dilated. Two kinds of inclusions were detected in BYMV-infected leaves: straight or slightly curved bands sometimes coiled or looped at the end, and electron opaque crystals with varied shapes. BYMV-infected cells showed lower chloroplast number in comparison to the control. Spraying of SA on faba bean leaves helped to reduce or prevent the harmful effects produced after virus infection. Application of 100 microM SA three days before inoculation restored the metabolism of infected leaves to the levels of healthy controls. SA treatment improved plant health by increasing the photosynthesis rates, pigment contents and levels of other parameters studied similar to control values. Moreover, SA treatment increased plant resistance against BYMV. This was observed through induction of chloroplast number, reduction in percentage of infected plants, decrease in disease severity and virus concentration of plants treated with SA prior to BYMV inoculation. Cells of SA-treated samples showed well-developed chloroplasts with many starch grains and well-organized cell organelles. The present results provide an overview of the negative effects on faba bean leaves due to BYMV infection from physiological and subcellular perspectives. Also, a role of SA involved in induction of resistance against BYMV infection in bean plants is discussed.

Transgenic Gladiolus plants transformed with the bean yellow mosaic virus coat-protein gene in either sense or antisense orientation.

Transgenic Gladiolus plants transformed with the bean yellow mosaic virus (BYMV) coat-protein (CP) gene in either sense or antisense (AS) orientation were developed using biolistics. Four of the plants were confirmed to carry the CP gene in the sense orientation of the gene and seven plants in the AS orientation. Two of the CP plant lines and all of the AS lines showed DNA rearrangements of the transgene in addition to an intact copy of the transgene. The copy number ranged from one to nine. Of the 11 lines, eight had only one to four copies of the transgene. Transcription of the transgene occurred for three of the CP lines and five of the AS lines as determined by Northern hybridization. All 11 plant lines were challenged with BYMV using controlled aphid transmission. One month following aphid transmission, the transgenic plants were examined by immunoelectron microscopy for presence of the virus. Several transgenic plant lines containing either antiviral transgene showed a lower incidence of infection (percentage of plants infected as detected by immunoelectron microscopy) than the non-transformed plants. Most of the CP- and AS-transgenic plants that did not contain BYMV 1 month after challenge were found to contain BYMV the next season. It appeared that BYMV infection was delayed in the CP- and AS-transgenic lines but that the transgenes did not prevent eventual infection of BYMV. This is the first report of developing a floral bulb crop with antiviral genes to BYMV.

First Report of Bean pod mottle virus in Soybean in Ohio.

Soybean has been increasing in importance and acreage over wheat and corn for the past decade in Ohio and is now planted on 4.5 million acres. Previous surveys in Ohio of viruses infecting soybean failed to identify Bean pod mottle virus (BPMV) and soybean virus diseases have rarely caused economic losses (1). During 1999, producers in Ohio noticed virus-like symptoms in soybeans in a few isolated locations. Soybeans with green stems, undersized and "turned up pods" were collected from Union, Wood and Wyandot Counties during October 1999 and soybeans with crinkled, mottled leaves were collected in Henry, Licking and Sandusky during August 2000. Five to six plants were collected from a single field from each county each year. In 1999, samples were sent to the University of Wisconsin-Madison, where one symptomatic leaflet/sample was ground in 3 ml of chilled phosphate buffered saline (pH 7.2). Leaf sap was placed in 1.5-ml centrifuge tubes and stored at 4°C for 24 h. Sap was assayed for the presence of BPMV using an alkaline phosphatase-labeled double-antibody sandwich enzyme-linked immunosorbent assay (DAS ELISA) for BPMV (AgDia Inc., Elkhart, IN). All samples tested were positive for BPMV. Samples collected in 1999 were also maintained at The Ohio State University in Harosoy soybean and in 2000 assayed serologically along with samples collected in 2000 for BPMV and Soybean mosaic virus (SMV) by ELISA and for Tobacco ringspot virus (TRSV) and Bean yellow mosaic virus (BYMV) by a host-range symptom assay; SMV, BYMV and TRSV had been identified from soybean in previous Ohio surveys. Soybean leaf samples were assayed using F(ab')2-Protein A ELISA with antiserum prepared in 1968 to a southern U.S. isolate of BPMV and to an Ohio isolate of Soybean mosaic virus (SMV) prepared in 1967, both stored at -20°C. Diseased and non-symptomatic soybean leaf samples were ground in 4 ml 0.025M Tris pH 8.0, 0.015M NaCl and 0.05% Tween 20. Extracts were tested for BPMV and SMV by ELISA following a protocol described elsewhere (2). All of the samples collected during 1999 and maintained in the greenhouse tested positive for both BPMV and SMV while all of those samples collected during 2000 tested positive for BPMV and negative for SMV. Host-range symptom assays were conducted with leaf extracts prepared by grinding 1 g tissue:10 ml potassium phosphate buffer, pH 7.0. Extracts were inoculated by leaf rub method to Harosoy soybean, Phaseolus vulgaris cvs. Red Kidney and Bountiful, cowpea, and cucumber. The host-range symptom assays of both the 1999 and 2000 samples were negative for TRSV and BYMV; cowpea failed to express local lesions and cucumber systemic mosaic characteristic of TRSV infection and the two Phaseolus cultivars the yellow mosaic characteristic of BYMV infection. These results indicate that both BPMV and SMV were present in the samples in 1999 but only BPMV in 2000. The distribution of BPMV within Ohio and economic impact of this virus have yet to be determined. This is the first report of BPMV in Ohio.

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.

Natural resistance to bean yellow mosaic potyvirus in subterranean clover

Seed of 31 named cultivars and 11 other genotypes of Trifolium subterraneum (subterranean clover) was sown in 3 major and 3 smaller scale field experiments. In these, bean yellow mosaic virus (BYMV) was spread from infector plants to test rows by naturally occurring aphids. The numbers of clover plants developing BYMV symptoms in each row were counted at different times. Based on the results from at least 2 field experiments, different genotypes were assigned to 1 of 5 BYMV infection categories (A-E), ranging from greatest (A) to least (E) infection. Category A was found to contain genotypes that were latest maturing while, except for cv. Rosedale (ssp. brachycalycinum) which was in E despite being of intermediate maturity, category E contained earliest maturing genotypes. Except for cv. Rosedale, when the percentages of plants with BYMV symptoms in the 3 main experiments were plotted against days to flowering previously established for each genotype, the two were closely related. However, when young plants of cultivars in categories D or E were aphid-inoculated with 2 BYMV isolates, they became infected to a similar extent to young plants of 2 late-maturing cultivars from category A. This suggests that, except for cv. Rosedale, the extent of BYMV infection obtained in the field was determined by plant physiological age, plants of late-maturing genotypes being easier for viruliferous aphids to infect with BYMV than plants of early-maturing genotypes of the same age but physiologically older, a phenomenon known as 'mature plant resistance'. When plants of cv. Rosedale were aphid-inoculated with 7 different isolates of BYMV, a systemic hypersensitive reaction developed with 5 isolates but not with two others. This suggests that cv. Rosedale has 'strain specific hypersensitive resistance' to BYMV. No systemic hypersensitive reaction developed when the same 7 BYMV isolates were aphid-inoculated to cv. Dwalganup and named selections Pink Flowered and Northam Early, genotypes previously reported to react hypersensitively to potyvirus infection. The field screening procedure employed is suitable for use by T. subterraneum breeding programs seeking to develop new cultivars with resistance to BYMV. Cultivar Rosedale may prove a suitable source of resistance to use as a parent in crossing programs aimed at producing cultivars with natural BYMV resistance.

Occurrence of bean yellow mosaic virus in subterranean clover pastures and perennial native legumes

In 1990, infection with bean yellow mosaic virus (BYMV) was widespread in subterranean clover (Trifolium subterraneum) pastures in the south-west of Western Australia. When 100 leaves were sampled at random per pasture, the virus was detected by ELISA in 23 of 87 pastures and incidences of infection ranged from 1 to 64%. BYMV was present in all seven districts surveyed, but highest incidences of infection occurred in the Busselton district. In smaller surveys in 1989 and 1992, incidences of infection in pastures were higher than in 1990, and ranged up to 90%. In 1992, when petals from 1703 samples of 59 species of perennial native legumes from 117 sites were tested by ELISA, only 1% were found infected with BYMV. The infected samples came from 5/7 districts surveyed. Species found infected were Kennedia prostrata, K. coccinea, Hovea elliptica and H. pungens. Representative isolates of BYMV from subterranean clover and native legumes did not infect white clover systemically confirming that clover yellow vein virus (CYVV) was not involved. It was concluded that BYMV infection was present in many subterranean clover pastures, but normally at low incidences, except in epidemic years such as 1992. Also, perennial native legumes are unlikely to act as major reservoirs for reinfection of annual pastures each year. In areas of Australia with Mediterranean climates where perennial pastures are absent, persistence of the virus over summer is therefore by some other method than infection of perennials.

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.