NCR200 - NIMSS



NCR200

Management Strategies to Control Major Soybean

Virus Diseases in the North Central Region

Period: February 2002 to February 2003

Meeting Dates: February 17 and 18, 2003

Members and Guests in Attendance:

Les Domier l.domier@uiuc.edu

Anne Dorrance dorrance.1@osu.edu

John Hill johnhill@iastate.edu

James Kurle kurle001@umn.edu

Les Lane llane/@unl.edu

Marie A.C. Langham marie_langham@sdstate.edu

Roberto Micheletti micheluttir@agr.gc.ca

Berlin Nelson Berlin.Nelson@ndsu.nodak.edu

Jim Schoelz schoelzj@missouri.edu

Steve Slack (AA) oardc@osu.edu

Albert Tenuta albert.tenuta@.on.Ca

Sue Tolin stolin@vt.edu

Minutes

Chair John Hill called the meeting to order, and introductions of all members and quests were made. The first order of business was to elect new officers. Marie Langham was nominated and elected by majority vote to serve as Secretary for the committee. Les Lane was nominated and unanimously elected to serve as Vice Chair and to become the next chair. A suggestion was made to have two e-mail listings: one with official members only and a second one with members and other interested parties.

Chair Hill (Iowa) started the meeting by discussing the two principal soybean viruses, bean pod mottle virus (BPMV) and soybean mosaic virus (SMV). BPMV, an approach for a short-term control measure, may be found by looking for reduced antigen load in the seed as opposed to looking at the foliar antigen load. Craig Grau (Wisconsin) and Chair Hill have been studying an approach to determine the antigen load in the seed. Companies favor selection of high yielding and low mottling soybean lines. However, this could favor the selection of a “Typhoid Mary”. Development of a virus index number might prevent this. For SMV, the RSV1 resistance gene is affective; however, this gene has a “two tiered mode of action” of with extreme resistance and hypersensitive reaction. Selection pressure on virus isolates has produced isolates with modified responses to this resistance. Les Domier (Illinois) inquired about experiments that were underway on BPMV transgenic resistance. Some research that was effective against BPMV (#2) was cited as being done at Pioneer and Monsanto. However, the history of companies dropping projects was cited as a problem to the control of these viruses. Chair Hill stated that the companies would have to play a role in the control of these viruses due to the problem of seed infection or contamination.

Les Domier began his report by reminding everyone of Glen Hartman’s presentation the previous day and their collaboration with the Illinois Natural History Survey. Through this program, they surveyed for bean leaf beetles and soybean aphids and collected plant samples for testing. Samples taken from every county with high BPMV incidence had not demonstrated a connection between Green stem and BPMV. Crosses are being done with low and high green stem incidence lines. Cage studies to evaluate the soybean aphid resistance of soybean cultivars are underway. Surveys were also done for Luetoviruses in soybean and legumes, but soybean dwarf virus (SbDV) has not been found. Discussion of the vectors for SbDV in the US and Japan followed. Les continued with a summary of their work with tobacco ringspot virus (TRSV) including seed to seed passage to promote seed transmissibility. Les Lane (Nebraska) inquired about old varieties with green stem. Was the rate the same or is this the result of a new susceptibility, cultural practices, or chemicals? Would older varieties that seemed to have lower green stem have the same level of green stem if they were planted today under today’s practices? Discussion followed on the impact of environmental stresses on virus and on the publication of data from environmental stresses research in on-line journals where the publication of climate-based research could be received favorably.

Les Lane discussed the research in Nebraska that Loren Geisler and he had in progress. Loren’s research included date of planting studies, field-testing of common soybean breeding lines and the top ten commercial varieties, and levels of insecticide. Les had been focusing on TRSV that had been found in Nebraska. Its symptomalogy varied from the classical bud blight. It will skip local lesions and become systemic. He intends to inoculate this strain to different soybean varieties. Chair Hill reminded everyone of the Plant Health Initiative website that would have space for the posting of evaluation research and the ability to indicate how it was done.

Berlin Nelson (North Dakota) contributed that during the past two years, they had surveyed 150 fields for BPMV, SMV, alfalfa mosaic virus (AMV), and tobacco streak virus (TSV). There were no positives found.

Roberto Micheletti (Canada) reported that this was the second year of a continuing survey for plant viruses in soybean. SMV, BPMV, TRSV, and AMV were found. SMV, BPMV, and TRSV had been found previously in soybean in Canada, but this is the first identification of AMV. TRSV was found in sixteen samples, SMV was diagnosed in thirteen samples, and twenty plants were positive for BPMV. Seed testing for BPMV and SMV from various soybean lines found only one positive test for SMV. Ninety-three bean leaf beetles tested for BPMV were found not to be positive. Discussion on the location of BPMV, SMV, and TRSV in the seed suggested varied locations for the different viruses and in different plants.

Jim Schoelz (Missouri) discussed the work done with Laura Sweets. All soybean samples positive for virus this year were BPMV with the exception of one that was positive for TRSV. Heavy beetle populations were present. One sample of AMV-infected Medicago was found. Sue Tolin (Virginia) commented that inoculating clovers were different and sometimes difficult. Marie Langham (South Dakota) commented about spreader rows.

Sue Tolin (Virginia) reported on genes that were introduced into Essex, resistance breaking in Hutchinson, field inoculations of SMV and BPMV, and dual inoculations.

Marie Langham (South Dakota) summarized studies on trials of inoculation techniques, insecticide trials for control of BPMV through control of the bean leaf beetle, and evaluations of soybean experimental lines and cultivars.

Steve Slack (Ohio) joined the group to discuss the websites, requirements of the committee, mailing lists, Appendix E, and members. He also addressed his role as administrator of the committee. His e-mail address is oardc@osu.edu.

Suggestions were made about soliciting the contributions of others, and the meeting was closed.

Individual State Reports

Presented at the Meeting

Illinois

Virus and virus research in Illinois

Surveys. The predominant virus found in Illinois over the last 3 years has been Bean pod mottle virus (BPMV). Other viruses have been found, but less frequently, including Soybean mosaic virus (SMV), Tobacco ringspot virus (TRSV), Tobacco streak virus (TSV), and Alfalfa mosaic virus. The soybean samples have been analyzed each year for Soybean dwarf virus (SbDV), but no SbDV infections have been detected in soybean.

Seed-coat mottling. Results from experiments conducted over 2 years indicated that plants infected with BPMV and SMV, alone or in combination, produced seed coat mottling, whereas noninoculated plants produced little or no mottled seed, indicating that virus infection of plants caused seed coat mottling and that most of the mottling of seeds observed in Illinois is due to BPMV. To investigate the genetics of seed coat mottling, crosses were made between soybean lines differing in their susceptibility to mottling.

Virus resistance. The ancestors of modern-day public soybean cultivars were evaluated for resistance to BPMV, SMV, and TSV. New sources of resistance are being confirmed in additional tests. Aphid resistance was reported for the first time in soybeans.

BPMV-SMV synergism. To investigate the synergistic interaction between BPMV and SMV, transgenic soybean plants expressing the SMV-G2 HC/Pro gene were produced. In addition, the accumulation and stability of BPMV RNAs in soybean plants infected with BPMV alone and in combination with SMV were evaluated over time.

Transmission through seed of SMV and TRSV. Crosses were made between soybean lines that differ in their rates of virus seed transmission. Isolates of SMV and TRSV with enhanced seed transmission were selected by repeatedly passing the viruses through seed. Infectious clones of the viruses are being constructed to identify virus sequences involved in seed transmission.

Iowa

Efforts are focused on bean pod mottle and soybean mosaic viruses. Research has developed short-term control measures that are focused on control of the disease caused by bean pod mottle virus. Potential inoculum sources in Iowa include seed transmission (< 0.1%), overwintered bean leaf beetles (ca. 1.5%), and Desmodium canadense. The relative potential importance of these sources is unknown. Tests to determine application of a long-lasting insecticide (Warrior) included treatment at VC, treatment at VC and ca. 10 days later, and treatment at VC and at the beginning of emergence of the first generation of beetles. As compared to the untreated control, the onset of the epidemic was reduced the greatest by treatment at VC and at the beginning of emergence of the first generation of beetles. This treatment also resulted in increased yield, enhanced seed quality (reduced seed-coat mottling), and reduced virus incidence. Date-of- planting experiments were conduced to evaluate delayed planting as a tactic for disease control. Over three years, results have been inconsistent with delayed planting resulting in reduced virus incidence and increased seed quality during only one year. Although the bean leaf beetle is regarded as the most important vector of the virus, the soybean leaf miner was also identified as a new virus vector. In studies of seed transmission, the relationship between seed-coat mottling and presence of virus in the seed has been shown to not be strongly correlated. Thus, seed-coat mottling is a poor indicator for presence of virus in seed.

Studies on soybean mosaic virus are focused on the mechanism of the Rsv1 resistance gene. The resistance gene is effective against all strains of the virus, except for strain G7, which can overcome the resistance gene and causes a hypersensitive response. The mode of action of the gene has been shown to confer a two-tiered response of extreme resistance (ER) followed, under certain conditions, by a hypersensitive response (HR) which is associated with elevation of PR1 (pathogenesis related) transcription. Continuous passage of strain G7 under the selection pressure of the Rsv1 gene has resulted in emergence of a new strain, which does not elicit the HR response, but caused systemic mosaic. Regions of the viral genome responsible for HR are being mapped. Soybean mosaic virus has also been developed for use as a transient expression vector in soybeans. Marker proteins GFP and GUS have been expressed in soybean plants using the virus vector.

Publications:

Giesler, L. J., Ghabrial, S. A., Hunt, T. E., and Hill, J. H. 2002. Bean pod mottle virus. A threat to U.S. soybean production. Plant Disease 86:1280-1289.

North Dakota

Berlin D. Nelson

In 2002, a survey for virus like diseases was conduced in 82 soybean fields in the principal soybean growing areas of the eastern part of North Dakota. Leaves were tested for Bean Pod Mottle Virus (BPMV), Soybean Mosaic Virus, Alfalfa Mosaic Virus and Tobacco Streak Virus using Agdia kits. There were no confirmed virus infections. In addition, food grade soybean seed was collected from 21 sources (grown in 2001) and seed coats were tested for BPMV. All seed tested negative. Growers of food grade beans were questioned about virus like problems and none reported any seed mottling problems in the 2001 crop. A Soybean Diseases web site for North Dakota was updated ( ) where information on diseases of soybean in North Dakota is placed.

South Dakota

SOYBEAN VIRUSES IN SOUTH DAKOTA

Marie A. C. Langham, Professor

Bean pod mottle virus (Genus: Comovirus; Family: Comoviridae) (BPMV) continues to be the most important viral disease affecting soybean production in South Dakota. High levels of BPMV were observed throughout the soybean production areas of the state. Bean leaf beetle (Ceratoma trifurcata Forster) spring emergence was delayed approximately ten days to two weeks from the two previous years and coincided with the germination and emergence of soybeans in many areas. High populations remained throughout the majority of the growing season. In 2002, field research centered on three areas: inoculation trials with high pressure spray inoculation, insecticide treatments for managing the bean leaf beetle and BPMV, and evaluation of soybean lines infected with BPMV. Cooperation with the extension pathologist, Dr. Martin Draper; the soybean breeder, Dr. Roy Scott; and the manager of the Southeast Research Farm, Dr. Robert Berg, has been a vital component of these projects.

Inoculation trials using high-pressure spray inoculation of BPMV were successful in field inoculation of soybean in contrast to earlier reports in the literature. In comparisons of mechanical transmission by hand, spray (50 PSI line pressure), spray (80 PSI line pressure), and noninoculated plants with two soybean varieties (Pioneer 92B23 and Pioneer 9233), hand inoculation produced 100% incidence of BPMV infected plants at all sampling dates. Incidence of infected plants inoculated at 50 PSI ranged from 33% at 3 wks post inoculation to 100 % at 9 wks post inoculation in Pioneer 9233 and from 35% at 3 wks post inoculation to 70% at 9 wks post inoculation in Pioneer 92B23. The incidence at 80 PSI inoculation for Pioneer 9233 ranged from 65% at 3 wks post inoculation to 97% at 9 wks post inoculation and for Pioneer 92B23 ranged from 65% at 3 wks post inoculation to 82% at 9 wks post inoculation. Disease incidence in the uninoculated controls ranged from 0 to 55% for Pioneer 9233 and from 15 to 45% for Pioneer 92B23. Correlations between disease incidence and final yield at 3 wks post inoculation were r = -0.77819 for Pioneer 92B23 and r = -0.72417 for Pioneer 9233. This strong correlation suggests that early season infection could be an important factor in predicting yield reductions. Correlations between disease incidence and yield were strong at 6 wks and 9 wks post inoculation for Pioneer 92B23, but were very low for Pioneer 9233. Disease incidence in Pioneer 9233 increased more rapidly than for Pioneer 92B23. This difference in disease incidence could have resulted in this variation in correlation. Inoculation trials are being expanded to compare four pressure rates at three inoculation dates.

Insecticide trials for control of BPMV and the bean leaf beetle comparing Pounce sprays (4 fl oz per acre) at 2 wks, 3 wks, 4 wks, 5 wks, 6 wks, 7 wks, and 8 wks post planting, weekly Pounce sprays, no insecticide treatment, and inoculation with BPMV and weekly insecticide sprays are continuing. Significant yield increases occurred in the Pounce at 6 wks post planting and the weekly Pounce treatments. The 6 wks treatment with Pounce coincided with the emergence of the first generation beetles. Analysis of other factors from this study is continuing. In separate soybean seed treatment experiments done by Dr. Martin Draper, seed treatment with Cruiser 400 CS (30 g ai/100 kg) demonstrated an increase on early and midseason stand counts, vigor, yield, and test weight.

Field evaluation of ten soybean experimental lines and cultivars for the effects of BPMV began this year in paired-plot field tests with no inoculation and inoculation with BPMV. These cultivars included: SD99-99R, SD99-48R, SD93-828E, SD00-1312R, SD99-026R, SD99-85R, SD99-096R, DK B28-51, T3205RR, and A2302. High-pressure spray inoculation of BPMV was utilized to infect the plants. Disease incidence was measured at 3, 6, and 9 wks post inoculation. Disease severity was rated weekly. Maturity dates, lodging, pod set and fill, heights, yields, test weight, seed quality, seed mottling, and seed oil and protein are being analyzed.

For 2002, BPMV remains the predominate virus disease in soybean. Inoculation studies and seed treatments with Cruiser indicate that early season beetle feeding and infection rates affect the yield and growth of South Dakota soybeans. Insecticide trials with Pounce indicate a significant improvement in yield when applied 6 wks post planting. This timing correlates with the emergence of the first generation of bean leaf beetles. These data support the value of early and midseason insecticide treatments being recommended in Iowa and other states. The ability to evaluate soybean lines as being done in our experimental trial will enhance the identification of resistant and tolerant soybean lines and cultivars. For the future, BPMV will remain a significant problem in South Dakota soybean production as long as abundant populations of bean leaf beetles continue. However, detection of the soybean aphid in twenty counties (Dr. Michael Catangui) strengthens concerns for the movement of soybean mosaic virus into South Dakota due to its role as a vector of this virus.

Additionally Contributed Report from NonCommittee Members

Canada

Soybean Virus Detection Activity 2002

NCR-200 Annual Meeting

Roberto Michelutti, Agriculture and Agri-Food Canada, Harrow, Ontario.

E-mail: micheluttir@agr.gc.ca

Activity 1. In spring 2002 ninety-seven samples of soybean breeding lines and varieties from the 2001 Ontario and Quebec crop were tested for SMV and BPMV presence in the seed. All lines were found to be negative for these viruses.

Activity 2. Five soybean breeding lines infected with SMV were divided in groups containing mottled seed, non-mottled seed, seed coat, and cotyledons and tested for the presence of SMV and BPMV in the seed. Only SMV was found in the mottled and non-mottled seed, in the seed coat (stronger signal) and in the cotyledons (weaker signal).

Activity 3. Mottled seeds from four soybean breeding lines were planted in four replicates and tested for the presence of SMV using ELISA at four different stages of growth. At the first stage of growth, one line was positive only in the roots. At the second stage of growth, another line was positive on the stem. At the third and fourth stages of growth all the plant parts were negative for SMV. The seeds of the same four breeding lines were used to determine the presence of SMV in different parts of the seed. Thirty seeds for each line were divided in: seed coat, cotyledon and embryo. Another set of thirty seeds were tested as a whole. SMV was detected only in the whole seed and the seed coat.

Activity 4. Ninety-three bean leaf beetles (Cerotoma trifurcata, Forster) found in two GPCRC fields were tested for BPMV and found non-infected. Monitoring these beetles for their presence and for their infection with bean pod mottle virus will continue.

Activity 5. Ninety soybean seed samples from breeding lines grown in Ontario during the 2001 season were tested for the presence of soybean mosaic virus (SMV) and bean pod mottle virus (BPMV) using ELISA. Only one sample was found to be infected with SMV.

Activity 6. For the second year a soybean survey was conducted in Ontario to search for soybean mosaic virus (SMV), bean pod mottle virus (BPMV), tobacco ringspot virus (TRSV) and, alfalfa mosaic virus (AMV). Young soybean leaf samples from over four hundred sites were processed and tested. A double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) was used to detect these viruses. A composite leaf sample from each site was homogenized with grinding buffer and loaded (2 replications) to an ELISA plate previously coated with the appropriate antibody (Agdia Inc., Elkart, IN). This test was done separately for each virus. Sixteen samples from sixteen different sites, collected from commercial fields spread from Essex County to Ottawa, tested positive for TRSV. Thirteen samples expanding from thirteen different sites, from commercial fields extending from Essex County to Ottawa, tested positive for SMV. Twenty samples from twenty different sites, from commercial fields located in Essex County, Grey County, and Ottawa region, tested positive for BPMV. Fifteen samples from fifteen different sites, from commercial fields extending from Essex County to Ottawa, tested positive for AMV. These four viruses were found in samples originating from soybean breeding nurseries. SMV, TRSV (Tu, 1988), and BPMV (Michelutti et al., 2001) have been found in Ontario previously, but, to our knowledge, this is the first report of AMV in soybean in Ontario. Further tests are needed to corroborate these findings. Additional surveys will be conducted in 2003.

Activity 7. A soybean survey was conducted in Quebec for the first year to test for the presence of soybean mosaic virus (SMV), bean pod mottle virus (BPMV), tobacco ringspot virus (TRSV) and, alfalfa mosaic virus (AMV). Forty-seven young soybean leaf samples were processed and tested. A double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) was used to detect these viruses. A composite leaf sample from each sample site was homogenized with grinding buffer and loaded (2 replications) to an ELISA plate previously coated with the appropriate antibody (Agdia Inc., Elkart, IN). This test was done separately for each virus. Seven samples tested positive for AMV, eight samples tested positive for TRSV, one sample tested positive for SMV and BPMV was not detected in any soybean sample. This is the first time, to our knowledge, that AMV and TRSV have been detected in soybeans in Quebec. Additional surveys will be conducted in 2003.

Co-operators:

Albert Tenuta – OMAF, Ridgetown College

Sylvie Rioux – CÉROM, Sainte-Foy

Terry Anderson – AAFC, Harrow

Tom Welacky – AAFC, Harrow

Vaino Poysa – AAFC, Harrow

Committee Leadership: John Hill, Chair, Iowa

Les Lane, Vice Chair, Nebraska

Marie Langham, Secretary, South Dakota

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