Progress 10/01/06 to 09/30/12
Outputs
OUTPUTS: Numerous experiments were completed during 2012; including field studies for management of Phytophthora root and stem rot caused by Phytophthora sojae, Pythium seedling blight, soybean cyst nematode, Charcoal rot caused by Macrophomina phaseolina, frogeye leaf spot caused by Cercospora sojina, sudden death syndrome caused by Fusarium virguliforme, seedling damping off caused by Rhizoctonia solani and Fusarium graminearum as well as white mold caused by Sclerotinia sclerotiorum at 3 OARDC Research Stations and 6 on-farm field sites. In addition we evaluated resistance to P. sojae in the US Public Breeders Uniform trial for Rps gene and partial resistance; as well as experiments to identify additional sources of resistance to many of these key pathogens. Two courses, Diseases of Field Crops and a special topics course, History of Host Resistance towards Plant Pathogens were taught. We hosted the North Central Division of the American Phytopathological Society in Wooster during June 2012. PARTICIPANTS: Dr. Hehe Wang, completed her Ph.D. and is now a post-doc at the USDA-ARS Horticultural Laboratory in Florida Dr. Asela Wijeratne and Saranga Wijeratne are from the Molecular Cellular Imaging Center at the OARDC. Dr. Steven St. Martin and Dr. Leah McHale are both soybean breeders in the Dept. of Horticulture and Crop Science at Ohio State University Dr. Henry Nguyen, Dr. Grover Shannon, Dr. V. Nguyen and Dr. Tri Vong are from the University of Missouri. We collaborated with them along with Dr. Tara Van Toai, USDA-ARS for studies that evaluated tolerance to flooding and resistance to Phytopthora sojae. Dr. Margaret Ellis also received her Ph.D. from Ohio State and is now post-doc at Iowa State University. TARGET AUDIENCES: Plant Breeders for molecular markers for specific genes associated with the expression of resistance to key pathogens of soybean Chemical companies that develop seed treatment compounds for the appropriate Pythium spp. that these produces should have efficacy towards. Ohio and north central soybean producers that have farm land that is prone to saturation and flooding, conditions that favor disease development. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Phytophthora sojae is the primary pathogen of soybeans that are grown on poorly drained soils. US and worldwide populations of P. sojae have adapted to the most commonly deployed resistance (Rps) genes. Thus much our work is focused on partial resistance. The detection of an individual QTL that confer partial resistance to P. sojae has differed across several studies depending on the specific pathogen isolate or phenotypic assay that was used. This study compared the QTL identified previously a population challenged with P. sojae isolate 1.S.1.1 to the QTL identified when this same population was challenged with two different isolates using a tray test assay. QTL were also mapped in the same population with isolate 1.S.1.1 using the layer test. Resistance QTL with smaller effects, especially those from the susceptible parent, were not consistently detected with the three isolates or the two phenotypic assays. Basic and composite interval mapping identified a major Conrad QTL on chromosome 18 and two on 19 that were detected with all three isolates and both phenotypic assays. We also mapped QTL associated with flooding tolerance and resistance to P. sojae from a cross between flood tolerant, PRR resistant genotype and flooding intolerant, P. sojae susceptible soybean genotype. Four genomic regions were associated with genetic control of decreased plant injury and higher yield under flooded conditions. Two of these regions were also associated with partial resistance to P. sojae. This indicates that genes for both flooding tolerance and resistance to P. sojae are necessary to reduce injury and yield loss under soil water logging and can contribute to increasing soybean productivity on soils prone to flooding. Another study focused on identifying mechanisms and molecular markers associated with partial resistance in the soybean cultivar Conrad. Two QTL on chromosome 19 were dissected through sequence and expression analysis of genes in both resistant (Conrad) and susceptible (Sloan) genotypes. Our findings indicate a complex defense network with multiple mechanisms underlying these QTL conferring resistance to P. sojae. SNP markers derived from these candidate genes can contribute to fine mapping of QTL and marker assisted breeding. Fusarium graminearum, has emerged as an important soybean seedling pathogen in Ohio. Five of 24 soybean genotypes evaluated had high levels of resistance to F. graminearum. Four putative QTL were identified from Conrad on chromosomes 8, 13, 15, and 16, and one putative QTL from Sloan were mapped. The QTL identified in this population were not the same as those that confer resistance to P. sojae, thus different loci are required for resistance to these two seedling pathogens. Two new species of Pythium which are pathogens of corn and soybean in Ohio are described. Pythium schmitthenneri sp. nov. and Pythium selbyi sp. nov. both have morphological and sequence characteristics that place them in Clade E1 of the genus Pythium. These new species were widely dispersed throughout the soybean and corn producing regions in Ohio, making their characterization critical for management.
Publications
- Wang, H., Wijeratne, A., Wijeratne, S., Lee, S., Taylor, C., St. Martin, S.K., McHale, L., and Dorrance, A.E. 2012. Dissection of two soybean QTL conferring partial resistance to Phytophthora sojae through sequence and gene expression analysis. BMC Genomics.2012, 13:428. DOI: 10.1186/1471-2164-13-428.
- Costamilan, L.M., Clebsch, C.C., Soares, R.M., Seixas, C.D.S., Godoy, C.V., and Dorrance, A.E. 2012. Diversity of Phytophthora sojae pathotypes from Brazil. European J. of Plant Pathol. DOI: 10.1007/s10658-012-0128-9.
- Nguyen, V.T., Vuong, T.D., VanToai, T., Lee, J.D., Wu, X., Mian M.A.Rouf, Dorrance, A.E., Shannon, J.G., and Nguyen, H.T. 2012. Mapping of quantitative trait loci associated with resistance to Phytophthora sojae and flooding tolerance in soybean. Crop Sci. 52:2481-2493.
- Ellis, M.L., Wang, H., Paul, P., St. Martin, S.K., McHale, L., and Dorrance, A.E. 2012. Identification of soybean genotypes resistant to Fusarium graminearum and genetic mapping of resistance quantitative trait loci in the cultivar Conrad. Crop Sci. 52:2224-2233.
- Ellis, M.L., Paul, P.A., Broders, K.D., and Dorrance, A.E. 2012. Two new species of Pythium, P. schmitthenneri and P. selbyi pathogens of corn and soybean in Ohio. Mycologia 104: 477-487.
- Wang, H., St. Martin, S.K., and Dorrance, A.E. 2012. Comparison of phenotypic methods and yield contributions of quantitative trait loci for partial resistance to Phytophthora sojae in soybean. Crop Science 52:609-622.
- Luster, D.G., McMahon, M.B., Edwards, H.H., Boerma, B.L., Lewis Ivey, M.L., Miller, S.A., and Dorrance, A.E. 2012. Novel Phakopsora pachyrhizi extracellular proteins are ideal targets for immunological diagnostic assays. AEM 78:3890-3895.
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: No soybean rust was identified in Ohio during 2011. In addition, no frogeye nor high levels of brown spot were reported at flowering; and temperatures were very high during flowering (<85 F). No fungicides were recommended for soybean rust, foliar diseases or Sclerotinia stem rot, thus saving producers money from unnecessary sprays. These recommendations were added to the Crop Observation and Recommendation Network Newsletter, weekly through the season, as well as several on-farm summer meetings. Phytophthora sojae, Pythium seedling diseases, sudden death syndrome, and soybean cyst nematode were prevalent this year. However, with one exception, much of the soybean crop received timely rains and the yields were very good, in spite of delayed planting, most of the crop went in the ground in June and excessive temperatures during July and August. PARTICIPANTS: Stewart, S. and Robertson, A.E. are collaborators from Iowa State University Zelaya-Molina, L.X was a visiting scholar from Mexico in the lab who worked on Phytophthora sojae. Broders, K., Ortega, M.A., Wang, H. and Ellis, M. are all graduate students in the Dept. of Plant Pathology that I advised. All of these students have successfully completed their degrees and one is now a faculty member at the Univ. of New Hampshire (Broders); Ortega is pursuing a Ph.D. at the University of Georgia; and Ellis will begin a post-doc at Iowa State University Sue Ann Berry, Damitha Wickramasinghe, Clifton Martin, Chrissy Balk, and Chanda Phelan are all Research Associates and Assistant in the Soybean Disease Lab under my supervision. Pierce Paul, is a collaborator at The Ohio State University Funding for these Projects was in part from Ohio Soybean Council, United Soybean Board, Iowa Soybean Association, Ohio Biotechnology Innovation Center, OARDC-MCIC TARGET AUDIENCES: Companies that develop soybean varieties, crop dealers, producers, extension educators and students through on-farm meetings, formal presentations, newsletters and publications. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Phytophthora root and stem rot caused by Phytophthora sojae, is one of the most damaging diseases of soybean, for which management is principally done by planting resistant cultivars with race specific resistance (Rps genes, Resistance to Phytophthora sojae). The Rps8 locus, identified in the South Korean landrace PI 399073, is located in a 2.23 Mbp region on soybean chromosome 13. In eight cv. Williams (rps8/rps8) x PI 399073 (Rps8/ Rps8) populations, this region exhibited strong segregation distortion. In a cross between the South Korean lines PI 399073 (Rps8/Rps8) and PI 408211B (multiple Rps genes) this region segregated in a Mendelian fashion. In this study, microsporogenesis was evaluated to identify meiotic abnormalities that may be associated with the segregation distortion of the Rps8 region. Pollen was collected from greenhouse-grown plants of the parental genotypes: Williams, PI 399073, and PI 408211B; as well as selected Rps8/rps8 RILs from Williams x PI 399073 BC4F2:3 and PI 399073 x PI 408211B F4:5 populations. There were no differences for pollen viability among the genotypes. However, for PI 399073, a mix of dyads, triads, tetrads and pentads was observed. A high frequency of meiotic abnormalities including fragments, laggards, multinucleated microspores; and microcytes containing DNA was also observed in Rps8/rps8 Williams x PI 399073 BC4F2:3 RILs. These meiotic abnormalities may contribute to the high degree of segregation distortion present in the Williams x PI 399073 populations. A simple and rapid DNA extraction protocol capable of obtaining high-quality and quantity DNA from oomycete plant pathogens was developed. Most DNA extraction protocols used with oomycete are relatively lengthy and cumbersome for high throughput analysis. Commercial kits are widely used, but low quantities of DNA are usually obtained, and with large scale analysis multiple isolations are required. The DNA obtained was used effectively in the amplification of microsatellite markers as well as specific genes. The protocol is inexpensive, easy, quick, and efficient in terms of the volume of reagents and the number of steps involved in the procedure. The method may be applicable to other oomycetes and effectively implemented in other laboratories. Fusarium graminearum causes seed decay and damping-off of soybean. Inoculum concentrations of 2.5 x 104 macroconidia/ml or higher were necessary for optimum disease development compared to lower inoculum levels of2.5 x 102, 2.5 x 103 at temperatures of 18 to 25 C. Seed treated with captan at 61.9 g a.i./100 kg or fludioxonil at 2.5 g a.i./100 kg or 5.0 g a.i./100kg developed smaller lesions than strobulurin based seed treatments and the non-treated control. Based on these results, there are limited choices in fungicide seed treatments for managing this seedling disease, and it is possible that shifts in seed treatment products as well as recent outbreaks in Fusarium head blight and ear and stalk rot may have played a role in the recent emergence of this soybean pathogen.
Publications
- Stewart, S., Wickramasinghe, D., Dorrance, A.E., and Robertson, A.E., 2011. Comparison of three microsatellite analysis methods for detecting genetic diversity in Phytophthora sojae (Stramenopila: Oomycete). Biotechnology Letters 33:2217-2223.
- Ortega, M. and Dorrance, A.E. 2011. Microsporogenesis of Rps8/rps8 heterozygous soybean lines. Euphytica 181:77-88.
- Zelaya-Molina, L.X, Ortega, M.A., and Dorrance, A.E. 2011. Easy and efficient protocol for oomycete DNA extraction suitable for population genetic analysis. Biotechnology Letters 33:715-720.
- Ellis, M.L., Broders, K.D., Paul, P.A., and Dorrance, A.E. 2011. Infection of soybean seed by Fusarium graminearum and effect of seed treatments on disease under controlled conditions. Plant Dis. 95: 401-407.
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: A recently described species of Phytophthora which is a pathogen of soybean and Douglas fir, Phytophthora sansomeana was recovered from corn seedlings in Ohio. Pathogenicity on corn was confirmed with Koch's postulates. Two separate studies in the lab this year identified novel QTL for P. sojae. The first study evaluated an interspecific recombinant inbred line (RIL) population from the cross of V71-370 by PI407162. Interval mapping located QTL for partial resistance to P. sojae on chrom. 16, 20, and 18. One of the QTL, on chr 16, accounted for 32, 42, and 22% of the phenotypic variation in the 2005, 2006a and 2006b experiments, respectively. In the second study, QTL on chromosomes 12, 13, 14, 17 and 19, each explaining 4-7% of the phenotypic variation, were identified using 186 RILs from a cross of the partially resistant cultivar Conrad and susceptible cultivar Sloan through composite interval mapping. Microarray analysis identified genes with significant differences in transcript abundances between Conrad and Sloan, both constitutively and following inoculation. Of these genes, 55 mapped to the five QTL regions. Ten proteins encoded genes with unknown functions, while the others encode proteins related to defense or physiological traits. Seventeen genes within the genomic region that encompass the QTL were selected and their transcript abundance was confirmed by qRT-PCR. Impact of brown spot on soybean caused by Septoria glycines is the most common foliar disease in Ohio. In the first study, yield loss associated with S. glycines was determined using weekly applications of chlorothalonil and the efficacy of azoxystrobin, pyraclostrobin, tebuconazole, and flutriafol alone and in combinations were also assessed using applications at the R3 and R5 growth stages at two locations over 3 years. Significantly different levels of brown spot developed following applications of chlorothalonil, with mean yield differences between treated and non-treated plots ranging from 196 to 293 kg/ha. Pyraclostrobin and azoxystrobin applied at the R3 growth stage significantly reduced final levels of brown spot; however, significant increases in yield only occurred in three of the six location-years. Triazoles, flutriafol, and tebuconazole, applied at R3 or R5 did not significantly decrease levels of brown spot or impact yield. In a second study, 37 large scale field size applications of fungicide were applied by producer cooperators to evaluate R3 timings of Quadris with and without Warrior insecticide in 2004 and 2005, and Headline, Folicur, Domark, or Headline plus Folicur in 2006, 2007 and 2008 in Ohio. Each trial was rated at growth stage R5 or R6 for incidence and severity of brown spot and frogeye leaf spot. a single application of fungicide(s) increased yield significantly in only six of the 28 locations; of which only three had yield increases greater than 4.2 bu/A. Populations of soybean aphids were high during 2005 at nine locations, and an insecticide application increased yield significantly at eight of the nine locations. PARTICIPANTS: Hehe Wang, Graduate research assistant Christian Cruz, Graduate Research assistant, completed M.S. degree Margaret Ellis, Graduate research assistant Lily Zelaya Molina, visiting scholar from Mexico. She returned after 9 months to pursue a degree in her home country. Dominic Tucker, M.A. Saghai Maroof,Brett Tyler and Inah Hoeschele collaborators from Virginia Tech, Blacksburg, VA Bender, R., Koenig, M., LaBarge, G., Leeds, R., Mangione, D., McCluer, G., Ruhl, S., Siegrist, H., Sundermeier, A., Sonnenberg, D., Yost, J., Watters, H., Wilson, G. are all county extension educators from Shelby, Sandusky, Fulton, Ross, Hardin, Morrow, Fairfield, Wood, Henry county, Ohio. TARGET AUDIENCES: There were two primary audiences with these research efforts soybean producers to help them make decisions about the use of fungicides in their crop soybean breeders to assist them in incorporating partial resistance into soybean lines PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Crop rotation may have limited impact in the future as several key root rot pathogens, a number of Pythium spp. as well as the newly identified Phytophthora sansomeana can infect both corn and soybean. A complex QTL-mediated resistance network which involves numerous pathways and several different mechanisms contribute to the high level of expression of resistance in the soybean cultivar Conrad. These studies will contribute to soybean resistance breeding by providing additional QTL for marker-assisted selection as well as a list of candidate genes which may be manipulated to confer resistance. Overall, yield loss contributed by Septoria glycines was low, but More data on the accurate timing of fungicides are still required to establish a long-term management program for this disease and resistance to brown spot should be monitored in soybean cultivar development to prevent future yield losses. From the large-farm size studies, yield loss can be significant when frogeye leaf spot and aphids are present early in the season.
Publications
- Wang, H., Waller, L., Tripathy, S., St. Martin, S.K., Zhou, L., Krampis, K., Tucker, D.M., Mao, Y., Hoeschele, I., Saghai Maroof, M.A., Tyler, B.M., and Dorrance, A.E. 2010. Analysis of genes underlying soybean quantitative trait loci conferring partial resistance to Phytophthora sojae. The Plant Genome 3: 23-40. Doi: 10.2835/plantgenome2009.12.0029.
- Cruz, C., Mills, D., Paul, P.A., and Dorrance, A.E. 2010. Impact of brown spot caused by Septoria glycines on soybean in Ohio. Plant Dis. 94: 820-826.
- Tucker, D.M., Saghai Maroof, M.A., Mideros, S., Skoneczka, J.A., Nabati, D.A., Buss, G.R., Hoeschele, I., Tyler, B.M., St. Martin, S.K., and Dorrance, A.E. 2010. Mapping quantitative trait loci for partial resistance to Phytophthora sojae in a soybean interspecific cross. Crop Sci. 50: 628-635.
- Dorrance, A.E., Cruz, C., Mills, D., Bender, R., Koenig, M., LaBarge, G., Leeds, R., Mangione, D., McCluer, G., Ruhl, S., Siegrist, H., Sundermeier, A., Sonnenberg, D., Yost, J., Watters, H., Wilson, G., and Hammond, R.B. 2010. Effect of foliar fungicide and insecticide applications on soybean in Ohio. Online. Plant Health Progress doi:10.1094/PHP-2010-0122-01-RS.
- Redinbaugh, M.G., Molineros, J.E., Vacha, J., Berry, S.A., Hammond, R.B., Madden, L.V., and Dorrance, A.E. 2010. Bean pod mottle virus spread in insect-feeding-resistant soybean. Plant Dis. 94: 265-270.
- Zelaya-Molina, L.X., Ellis, M.L., Berry, S.A., and Dorrance, A.E. 2010. First report of Phytophthora sansomeana causing wilting and stunting on corn in Ohio. Plant Dis. 94: 125.
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: No soybean rust was identified in Ohio during the 2009 season in Ohio. No fungicides were recommended for soybean rust. During 2009, there were positive finds of soybean rust spores in rainfall spore traps in southwest Ohio. Extensive sampling following these finds indicated that no infections occurred. Sclerotinia sclerotiorum, sudden death syndrome, soybean cyst nematode and Phomopsis seed rot were very prevalent this year due to extended periods of cool temperatures and moisture. A study which evaluated several traits of the fungus, Cercospora sojina, which may have contributed to the increase in incidence of frogeye leaf spot (FLS) in Ohio was completed. Conidia of C. sojina were recovered from soybean debris collected at two locations from December to May 2007-08. The optimum temperature for mycelial growth of all isolates evaluated in this study including those from Louisiana and Southern Illinois was 25C. The 50 isolates of C. sojina collected in Ohio were able to infect a mean of 4.9 of 12 differentials and had a total of 20 different pathotypes. The Rcs3 gene conferred resistance to all of the Ohio isolates. Another study examined the relationship of soil physical and chemical properties with Pythium communities and species diversity, and variability in disease incidence among communities. A high-throughput baiting and identification process identified more than 7000 isolates of Pythium from 88 locations in Ohio. Isolates were identified using Direct colony-PCR followed by Single strand conformation polymorphisms. A multi-state study evaluated the effect of seed treatments on the incidence and severity of Phytophthora root and stem rot on soybeans with different combinations of Rps genes and levels of partial resistance. The efficacy of the seed treatments was highly variable across locations. Seed treatments (metalaxyl and mefenoxam) provided protection and increased yields across cultivars in locations where rain or irrigation occurred shortly after planting (Ohio, South Dakota and Ontario). However, there were no significant differences in stand or yield consistently across cultivars in Iowa, Nebraska, Wisconsin, or Ohio where heavy precipitation did not occur until later growth stages. In a related study, Twenty-one microsatellite markers were developed for the oomycete, Phytophthora sojae. PARTICIPANTS: Dr. Anne E. Dorrance (PI) Dr. Kirk Broders (Ph.D.) Christian Cruz (M.S.) Grant Austin, summer intern Sue Ann Berry Alison Robertson, Department of Plant Pathology, Iowa State University, Ames, IA Loren Giesler, Department of Plant Pathology, University of Nebraska, Lincoln, NE Craig Grau, Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706-1598 Martin Draper, Plant Science Department, South Dakota State University, Brookings, SD 57007-1090 Albert Tenuta, Ontario Ministry of Agriculture, Food and Rural Affairs, Ridgetown, Ontario, Canada, N0L 2C0 Terry Anderson, Agriculture and Agri-Food Canada, Harrow, Ontario, Canada, N0R 1G0 Nik Grunwald, Horticultural Crops Research Laboratory, US Department of Agriculture, Agricultural Research Service, Corvallis, OR, USA TARGET AUDIENCES: Soybean producers, soybean agronomists, crop consultants, soybean breeders, soybean seed companies These data have been presented at numerous producer meetings, lectures and demonstrations at Ohio Foundation Seeds, regional meetings with colleagues. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Survival of Cercospora sojina in the field during the winters of 2005 to 2007 contributed to the increase of C. sojina during the 2005, 2006 and 2007 production seasons in Ohio. There was a strong association between abiotic soil components and the structure of Pythium communities, as well as diversity of Pythium species collected from agronomic production fields in Ohio. The environment, levels of inoculum, as well as, pathogen complex may have played a role in the different responses to the seed treatments and to the different combinations of Rps genes and levels to partial resistance to P. sojae in the cultivars. Fields which are poorly drained and have P. sojae populations with complex pathotypes may benefit the most from seed treatments. Based on the SSR analysis, evidence for outcrossing was observed in a small sample of Phytophthora sojae collected from Ohio.
Publications
- Dorrance, A.E., Robertson, A.E., Cianzo, S., Giesler, L.J., Grau, C.R., Draper, M.A., Tenuta, A.U., and Anderson, T.R. 2009. Integrated management strategies for Phytophthora sojae combining host resistance and seed treatment. Plant Dis. 93: 875-882.
- Broders, K.D., Wallhead, M.W., Austin, G.D., Lipps, P.E., Paul, P.A., Mullen R.W. and Dorrance, A.E. 2009. Association of soil chemical and physical properties with Pythium species diversity, community composition, and disease incidence. Phytopathology 99:957-967.
- Cruz, C.D. and Dorrance, A.E. 2009. Characterization and survival of Cercospora sojina in Ohio. Online. Plant Health Progress doi:10.1094/PHP-2009-0512-03-RS.
- Dorrance, A.E. and Grunwald, N.J. 2009. Phytophthora sojae: Diversity among and within populations. In Oomycete Genetics and Genomics: Biology Interactions with Plant And Animals and Toolbox. Editors K. Lamour and S. Kamoun. John Wiley & Sons, Inc. pp 197-212.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Dorrance, A.E. 2008. Management of Phytophthora sojae. Focus on Soybean. www.plantmanagementnetwork.org. This is a 15 minute presentation that is available through the Plant Management Network. Kirk D. Broders received his Ph.D. in December, 2008. Christian Cruz received his M.S. in December 2008. PARTICIPANTS: Monitoring for soybean rust is a national effort coordinated through Soybean check-off monies from both United Soybean Board, North Central Soybean Research Project coordinated by Dr. Don Hershman, University of Kentucky and Dr. Loren Giesler, University of Nebraska and USDA-CSREES through the ipmPIPE coordinated by Dr. Jim VanKirk, southern IPM. Spore trapping efforts are lead by Dr. Les Szabo at the USDA-ARS Rust Lab. Sue Ann Berry, Research associate, who assisted in the preparation of the diagnostic guide. Collaborator was Dr. Terry Anderson, Agriculture and Agri-Food Canada, Harrow, Ontario Canada provided additional information on the modifications that they use in their work. Dr. Xiamoei Guo and Dr. Dechun Wang, from Michigan State University were collaborators on the Sclerotinia project. In this study we each mapped a different population then pooled our results for one paper. A former post-doc in my lab, Dr. Stuart Gordon contributed to the mapping. Ms. Emily Helliwell and Trista Smith were interns working in the lab who performed all of the characterization of the lines. TARGET AUDIENCES: Soybean producers, chemical dealers, soybean seed suppliers, certified crop advisors, county extension educators, soybean germplasm suppliers, soybean seed companies, research technicians, diagnosticians, colleagues at other land-grant institutions. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Cris Report - 2008 Disease management: Soybean Producers saved money in 2008 on production cost as no soybean rust was identified in Ohio during the 2008 season in Ohio nor were conditions favorable for the build up and spread of Cercospora sojina, the causal agent of frog eye leaf spot. Students, diagnosticians, research technicians in both industry and academia have a new resource for working with Phytophthora sojae. P. sojae has increased in prevalence in the past decade and this diagnostic guide focuses on isolation of P. sojae, characterizing pathotypes, and screening for resistance in soybeans. Sclerotinia sclerotiorum, which causes Sclerotinia stem rot, continues to plague some regions in the US. The best management strategy is plant soybean varieties with resistance to this pathogen. New alleles for resistance were mapped in PIs 391589A and 391589B, which offer breeders another genetic resource.
Publications
- Guo, X., Wang, D., Gordon, S.G., Helliwell, E., Smith, T., Berry, S., St.Martin, S.K., and Dorrance, A.E. 2008. Genetic mapping of QTLs underlying partial resistance to Sclerotinia sclertotiorum in soybean PI 391589A and PI 391589B. Crop Sci. 48: 1129-1139.
- Dorrance, A.E., Berry, S.A., Anderson, T.R., and Meharg, C. 2008. Isolation, storage, pathotype characterization and evaluation of resistance for Phytophthora sojae in soybean. Plant Health Progress doi:10.1094/PHP-2008-0118-01-DG.
- Mian, M.A., Cooper, R.L. and Dorrance, A.E. 2008. Registration of Strong-Rps1k Soybean Germplasm. Journal of Plant Registrations. 2:143-145.
- St. Martin, S.K., Feller, M.K., McIntyre, S.A., Fioritto, R.J., Dorrance, A.E., Berry, S.A., and Sneller, C.H. 2008. Registration of Dennison soybean. Journal of Plant Registrations 2:21.
- Baysal-Gurel, F., Ivey, M.L.L., Dorrance, A., Luster, D., Frederick, R., Czarnecki, J., Boehm, M. and Miller, S.A. 2008. An immunofluorescence assay to detect urediniospores of Phakopsora pachyrhizi. Plant Disease 92: 1387-1386.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: The results from the weekly sentinel plot surveys were reported both in the USDA, IPM PIPE website interface but more importantly 33 newsletter articles in Ohio's Agronomic Crop Newsletter, C.O.R.N. Posters and presentations were made at scientific meetings throughout the year in 2007 including the Asilomar Conference for Oomycete genetics in March, invited plenary session speaker at the North Central Division of American Phytopathological Society, Featured topic in the Annual meeting of American Phytopathological Society "Flash and Dash" as well as extension presentations in the state.
PARTICIPANTS: Dr. Anne Dorrance is the lead PI on all projects with graduate students, Kirk Broders, Hehe Wang, Maria Andrea Ortega, Margaret Ellis, Zhifen Zhang and Christian Cruz. In addition, two Post-docs Stuart Gordon and Julio Molineros contributed to the progress this past year. Visiting scholar, Wirat Pipatpongpinyo and undergraduate interns, Chris Woltjen, Bryan Reeb, Matt Wallhead and Grant Austin also contributed. Partner organizations are many, primarily The Ohio Soybean Council, North Central Soybean Research Program, Iowa Soybean Board, USDA, IPM-PIPE, as well as collaborators from Virginia Tech, Iowa State University, North Dakota State University, South Dakota State University, Univ. of Minnesota, Univ. of Wisconsin, Univ. of Illinois, Nebraska State Univ-Lincoln, University of Missouri, Purdue Univ., Michigan State Univ., Univ. of Kentucky, Mississippi State Univ. Univ. of Florida, Univ. of Georgia, North Carolina State Univ., Texas A&M.
TARGET AUDIENCES: Producers, commodity organization representatives, ag-chem dealers - 40% of the effort in disease management recommendations. While graduate students, post-docs and those in seed industry for 60% effort
Impacts
Disease management: No soybean rust was identified in Ohio during the 2007 season in Ohio. No fungicides were recommended for soybean rust. Frogeye leaf spot was reported in mid June in the western part of the state and then numerous counties shortly thereafter. During 2007, there were three positive finds of soybean rust spores in rainfall spore traps as well as one positive "rust-like" spore in a Syngenta trap. Extensive sampling following these finds indicated that no infections occurred. Extensive sampling during mid-October failed to find any leaves with soybean rust in Ohio along Route 30. During the springs of 2004 and 2005, 112 isolates of F. graminearum were recovered from diseased corn and soybean seedlings from 30 locations in 13 Ohio counties. These isolates were evaluated in an in vitro pathogenicity assay on both corn and soybean seed, and 28 isolates were tested for sensitivity to the seed treatment fungicides azoxystrobin, trifloxystrobin, fludioxonil,
and captan. All of the isolates were highly pathogenic on corn seed, and moderately to highly pathogenic on soybean seed. Fludioxonil was the only fungicide that provided sufficient inhibition of mycelial growth, however several fludioxonil resistant mutants were identified during the sensitivity experiments. These results indicate that F. graminearum is an important pathogen of both corn and soybean seeds and seedlings in Ohio, and that continued use of fludioxonil may potentially select for less sensitive isolates of F. graminearum. Partial resistance to P. sojae in soybeans is effective against all the races of the pathogen and is a form of incomplete resistance in which the level of colonization of the root is reduced following inoculation. Other forms of incomplete resistance include the single dominant gene Rps2 and Ripley's root resistance, which are both race-specific. To differentiate partial resistance from the other types of incomplete resistance the components: lesion
length, numbers of oospores and infection frequency were measured in eight soybean genotypes inoculated with two P. sojae isolates. The Rps2 and root resistant genotypes had significantly lower oospore production and infection frequency compared to the partially resistant genotype Conrad while root resistant genotype also had significantly smaller lesion lengths. However, the high levels of partial resistance in Jack were indistinguishable from Rps2 in L76-1988 based on the evaluation of these components. Root resistance in Ripley and Rps2 in L76-1988 had similar responses for all components measured in this study. Partial resistance expressed in Conrad, Williams, Jack and General was comprised of various components that interact for defense against P. sojae in the roots and different levels of each component were found in each of the genotypes. However, forms of incomplete resistance expressed via single genes in Ripley and Rps2 in L76-1988, could not be distinguished from high
levels of partial resistance based on lesion length, oospore production and infection frequency.
Publications
- Dorrance, A.E., Mills, D., Robertson, A.E., Draper, M.A., Giesler, L. and Tenuta, A. 2007. Phytophthora root and stem rot of soybean. The Plant Health Instructor. DOI 10.1094/PHI-I-2007-0830-07 (http://www.apsnet.org/education/LessonsPlantPath/PhytophthoraSojae/d efault.htm).
- Broders, K.D., Lipps, P.E., Paul, P.A. and Dorrance, A.E. 2007. Evaluation of Fusarium graminearum associated with corn and soybean seed and seedling disease in Ohio. Plant Disease 91:1155-1160.
- Mideros, S., Nita, M., and Dorrance, A. E. 2007. Characterization of components of partial resistance, Rps2, and root resistance to Phytophthora sojae in soybean. Phytopathology 97: 655-662.
- Broders, K.D., Lipps, P.E., Paul, P.A., and Dorrance, A.E. 2007. Characterization of Pythium spp. associated with corn and soybean seed and seedling disease in Ohio. Plant Disease 91:727-735.
- Ziems, A.D., Giesler, L.J., Graef, G.L., Redinbaugh, M.G., Vacha, J.L., Berry, S.A., Madden, L.V. and Dorrance, A.E. 2007. Response of soybean cultivars to Bean pod mottle virus invection. Plant Dis. 91:719-726.
- Gordon, S. G., Kowitwanich, K., Pipatpongpinyo, W., St. Martin, S. K., and Dorrance, A. E. 2007. Molecular marker analysis of soybean plant introductions with resistance to Phytophthora sojae. Phytopathology 97:113-118.
- Gordon, S. G., Berry, S. A., St. Martin, S. K., and Dorrance, A. E. 2007. Genetic analysis of soybean plant introductions with resistance to Phytophthora sojae. Phytopathology. 97:106-112.
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Progress 01/01/06 to 12/31/06
Outputs
The number of resistance genes which confer resistance to Phytophthora sojae was determined in 22 plant introductions (PI) from South Korea. F2:3 and F2:4 families from crosses of the PIs and Williams were inoculated with P. sojae OH17 (vir 1b, 1d, 2, 3a, 3b, 3c, 4, 5, 6, 7), and OH25 (1a, 1b, 1c, 1k, 7). These isolates were selected because they are virulent on soybeans with all known Rps genes and many Rps gene combinations. In two PIs, resistance was conferred by two genes to OH17 and three genes to OH25. Resistance to both isolates was conferred by a single gene in PI 398440 although the individual families were not resistant to the same isolates. The data suggest that six of the populations have three Rps gene combinations as previously proposed while another four may have either a novel Rps gene or a four-Rps gene combination. The objective of this study was to determine if the Rps genes present in these PIs were associated with eight described Rps loci that
have been mapped on soybean molecular linkage groups (MLG) F, G, J and N. Nine F2:3 soybean populations were genotyped with simple sequence repeat (SSR) markers linked to previously mapped Rps loci. The nine PI populations all had SSR markers associated (P<0.01) with resistance to P. sojae isolate OH17 in the Rps1 region. Rps1c is a likely candidate in eight PIs but novel genes may also be possible while novel genes may confer resistance in one PI to P. sojae isolate OHI7. Two or more Rps genes, including some that are potentially novel, confer resistance to P. sojae isolate OH25 in eight of the populations. However, based on the response to these two isolates, virulence already exists for at least some of the novel genes identified in this study. Cool moist conditions in combination with minimum tillage, earlier planting, and recent shifts in commercial fungicide seed-treatment active ingredients have led to an increase in corn and soybean seedling establishment problems. This
situation resulted in an investigation of Pythium species associated with seed and seedling diseases. Samples of diseased corn and soybean seedlings were collected from 42 production fields in Ohio. Eleven species and two distinct morphological groups of Pythium were identified, of which six species were moderately to highly pathogenic on corn seeds and nine species were highly pathogenic on soybean seeds. There was significant variation (P<0.05) in sensitivity to mefenoxam, azoxystrobin, trifloxystrobin, and captan both across and within species. Multiple species of Pythium had the capacity to reduce germination of both corn and soybean seeds. Results indicated that mefenoxam, azoxystrobin, trifloxystrobin, or captan when used individually, may not inhibit all pathogenic species of Pythium found in Ohio soils
Impacts
Putative new resistance genes to Phytophthora sojae have been identified in a number of plant introductions. Further work is necessary to characterize these, but some may already have populations of P. sojae that these genes are not effective against New recommendations on the use of fungicide seed treatments for some areas of Ohio can be made. A seed treatment, comprised of multiple modes-of-action may be necessary for the fields with long histories of stand issues.
Publications
- Tyler, B.M., Tripathy, S., Zhang, X., Dehal, P., Jiang, R.H.Y., Aerts, A., Arredondo, F.D., Baxter, L., Bensasson, D., Beynon, J.L., Chapman, J., Damasceno, C.M.B., Dorrance, A.E., Dou, D., Dickerman, A., Dubchak, I.L., Garbelotto, M., Gijzen, M., Gorgon, S.G., Govers, F., Grunwald, N.J., Huang, W., Ivors, K.L., Jones, R.W., Kamoun, S., Krampis, K., Lamour, K.H., Lee, M., McDonald, W.H., Medina, M., Miejer, H.G.G., Nordber, E.K., Maclean, D.J., Ospina-Giraldo, M.D., Morris, P.F., Phuntumart, V., Putnam, N.H., Rash, S., Rose, J.K.C., Sakihama, Y., Salamov, A.A., Savidor, A., Schuering, C.F., Smith, B.M., Sobral, B.W.S. Terry, A., Torto-Alalibo, Win, J., Xu, Z., Zhang, H., Grigoriev, I.V., Rokhsar, D.S., and Boore, J.L. 2006. Phytophthora genome sequences uncover evolutionary origins and mechanisms of pathogenesis. Science 313:1261-1266.
- Hoitink, H.A.J., Madden, L.V. and Dorrance, A.E. 2006. Systemic resistance induced by Trichoderma spp.: Interactions between the host, the pathogen, the biocontrol agent, and soil organic matter quality. Phytopathology 96:186-189.
- Gordon, S.G., St.Martin, S.K., and Dorrance, A.E. 2006. Rps8 Maps to a resistance gene rich region on soybean molecular linkage group F. Crop Sci. 46:168-173.
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Progress 01/01/05 to 12/31/05
Outputs
Partial resistance and R-genes for Phytophthora sojae are critical avenues of management of this soil-borne pathogen. Progress was made this year on two fronts, identifying defense pathways involved in partial resistance to P. sojae and mapping Rps8 in a large population. In addition, evaluations of seed treatments and cultural practices to manage P. sojae, R. solani and F. solani f. sp. glycines were also completed. More importantly, fungicides were evaluated for plant health benefits but also any effect on foliar diseases in Ohio. Soybean cultivars with resistance to P. sojae, Sclerotinia and F. solani f.sp. glycines were also evaluated in field studies. Constitutive levels of expression of defense-related genes were examined in a series of cultivars with different levels of partial resistance to P. sojae by northern blot analysis. Pearsons correlations between mean lesion length and mean constitutive mRNA signals for defense-related genes showed no significant
association to partial resistance to P. sojae. These results suggested that mechanisms linked to defense-related mRNA levels expressed during infection might better explain variations in partial resistance to P. sojae in soybean. Second, accumulation of four defense-related transcripts during infection was monitored in a spatial, time-course infection assay with two soybean cultivars, Conrad (high level of partial resistance) and OX 20-8 (Rps1a, low level of partial resistance). Differential mRNA accumulation patterns for both soybean and P. sojae actin following P. sojae colonization in the three root sections of Conrad and OX 20-8 suggested that effective lesion-limiting mechanisms occurred primarily in the upper root section. Transcript levels for PR1a, matrix metalloproteinase (MMP) and basic peroxidase (IPER) at the inoculation site; and IPER above the inoculation site at 72 hai were significantly higher in Conrad with higher levels of partial resistance. Our results suggest that
defense responses associated with accumulation of PR1a, MMP, IPER and B-1, 3-endoglucanase (EGL) mRNAs may contribute to the partial resistance response to P. sojae in soybean. The objective of this study was to verify the genomic location of Rps8 in a larger population of 138 F2:3 families with SSR and RFLP markers. Based on linkage analysis with SSR and RFLP markers, Rps8 was located on molecular linkage group F in this population. This region of the soybean genome contains numerous other resistance gene loci as well as pathogen and pest resistance QTL.
Impacts
Identified and mapped a new resistance gene for Ohio, and many areas of the midwest, primary soybean disease pathogen, P. sojae. Verified that this new resistance gene will be effective against Ohio's P. sojae populations. Identified defense pathways, time and location of expression for partial resistance to P. sojae. This will facilitate future work on mechanisms of this resistance.
Publications
- Vega-Sanchez, M., Redinbaugh, M.G., Costanzo, S., and Dorrance, A.E. 2005. Spatial and temporal expression analysis of defense-related genes in soybean cultivars with different levels of partial resistance to Phytophthora sojae. Physiological and Molecular Plant Pathology. 66:175-182.
- Gordon, S.G., St.Martin, S.K. and Dorrance, A.E. 2005. Rps8 maps to a resistance gene rich region on soybean linkage group F. Crop Science 46:168-173.
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Progress 01/01/04 to 12/31/04
Outputs
Studies which examine seed treatments, deployment of partial resistance with and without Rps genes, and the effects of different levels of soil moisture were evaluated during 2004. Seed treatments at the highest rates of metalaxyl or mefenoxam gave the best protection. Cultivars with low levels of partial resistance, with and without Rps genes, lost more stand than the cultivar with highest levels of partial resistance. Mapping efforts are still in progress to locate novel Rps genes in a collection of South Korean PIs. Mapping of resistance QTLs in PI391589A for Sclerotinia is also still in progress
Impacts
Decreases losses due to Phytophthora sojae based on the using the appropriate rate of fungicide as well as more data that supports planting cultivars with high levels of partial resistance.
Publications
- Dorrance, A.E., Jia, H. and Abney, T.S. 2004. Evaluation of soybean differentials for their interaction with Phytophthora sojae. Plant Health Progress. doi:10.1094/PHP-2004-0309-01-RS.
- Dorrance, A.E., Berry, S.A., Bowen, P. and Lipps, P.E. 2004. Characterization of Pythium spp. from three Ohio fields for pathogenicity on corn and soybean and metalaxyl sensitivity. Plant Health Progress doi:10.1094/PHP-2004-0202-01-RS.
- Grau, C.R., Dorrance, A.E., Bond, J. and Russin, J.S. 2004. Fungal Diseases. In: Soybeans: Improvement, Production, and Uses, 3rd ed. Agronomy Monograph no. 16. H.R. Boerma and J.E. Specht. Ed. p. 679-763.
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Progress 01/01/03 to 12/31/03
Outputs
Partial resistance to Phytophthora sojae in soybean is expressed as a reduced level of root rot and is effective against all populations of the pathogen. The objective of this study was to identify simple sequence repeat (SSR) markers associated with putative quantitative trait loci (QTL) for partial resistance to P. sojae in the soybean cultivar Conrad. Three recombinant inbred soybean populations, Conrad x Sloan, Conrad x Harosoy, and Conrad x Williams; were evaluated for root lesion growth rate in growth chamber experiments following inoculation with P. sojae and with SSR markers to identify putative QTLs. The three populations segregated for root lesion growth rate after root inoculations. Family mean heritability estimates for the three populations were 0.62, 0.87, and 0.59 for the F4:6 generation. Two putative QTLs donated by Conrad were identified in all three populations and were positioned on soybean molecular linkage groups (MLG) F and D1b+W. The QTL on MLG
F explained 32.4, 35.0, and 21.4 percent of the genotypic variation for Conrad x Sloan, Conrad x Harosoy, and Conrad x Williams populations, respectively. The QTL on MLG D1b+W explained 10.6, 15.9, and 20.7 percent of the genotypic variation for the same three populations, respectively. The QTL on MLG F appears to be of more value based on the percent of genotypic variation explained. Because the results indicate that QTLs for partial resistance to P. sojae map to different regions in soybean compared to the known Rps genes poses a challenge to soybean breeders. Marker assisted selection may expedite the process of combining both Rps genes with partial resistance into high yielding cultivars. Bean pod mottle virus (BPMV) has emerged as a new pathogen of soybeans in Ohio along with increased populations of its vector, the bean leaf beetle. The presence of this virus is believed to contribute to higher incidence of seed coat mottling and soybean stems that remain green after pods mature
have occurred. Resistance to the virus has not been identified, but resistance to insect feeding may play a role in reducing overall incidence of this virus. Our studies are designed to determine if incorporating resistance to insect feeding could serve as an integrated pest management strategy for reducing losses associated with BPMV Pythium spp. were baited with corn and soybean seed from soils collected from three locations in Ohio where soybean and corn stand establishment was a concern. Five species, P. catenulatum, P. irregulare, P. paroecandrum, P. splendens and P. torulosum, were recovered and a subset of these isolates was then tested for pathogenicity on corn and soybean seed and sensitivity to the seed treatment fungicide metalaxyl. There was a range of both pathogenicity and sensitivity to metalaxyl within and among the Pythium spp. recovered from the three locations. A more thorough evaluation of the Pythium populations that exist in grain production fields in the north
central region of the US is needed to facilitate the development and deployment of broader based seed treatment products.
Impacts
Loci which contribute to partial resistance to Phytophthora sojae have been identified with SSR markers at locations. These findings will assist companies in developing lines with higher levels of partial resistance Soybean lines with resistance to insect feeding maybe a means to manage spread and reduce incidence of BPMV Pythium spp. maybe playing a more important role in corn and soybean seedling establishment. More research is needed on the occurrence, species and fungicide sensitivity of these seedlng pathogens.
Publications
- Dorrance, A.E., McClure, S.A. and St.Martin, S.K. 2003. Effect of partial resistance on Phytophthora root and stem rot incidence and yield of soybeans in Ohio. Plant Dis. 87: 308-312.
- Dorrance, A.E., McClure, S.A. and de Silva, A. 2003. Pathogenic Diversity of Phytophthora sojae in Ohio soybean fields. Plant Dis. 87:139-146.
- Burnham, K.D., Dorrance, A.E., VanToai, T.T. and St.Martin, S.K. 2003. Quantitative trait loci for partial resistance to Phytophthora sojae in soybean. Crop Sci. 43:1610-1617.
- Vega-Sanchez, M.E. 2003. Defense-related Gene Expression in Soybean Cultivars with Different Levels of Partial Resistance to Phytophthora sojae. M.S. Thesis, The Ohio State University
- Jia, H. 2003. An Evaluation of Protocols for Stabilizing Pathotypes of Phytophthora sojae isolates and Characterizing Race-specific Resistant in Genes in Soybean Plant Introductions. M.S. Thesis, The Ohio State University.
- Redinbaugh, M.G., Vacha, J.L., Berry, S.A. and Dorrance, A.E. 2003. Comparison of Early and Late Inoculations of Ohio Soybean Germplasm with Bean Pod Mottle Virus. Phytopathology 93: Supplement S73.
- Dorrance, A.E., Berry, S.A., Bowen, P., and Lipps, P.E. 200x. Characterization of Pythium spp. from three Ohio fields for pathogenicity and metalaxyl sensitivity. Plant Health Progress. Accepted
- Dorrance, A.E., Kleinhenz, M.D., McClure, S.A. and Tuttle, N. 2003. Temperature, moisture and seed treatment effects of Rhizoctonia solani root rot of soybean. Plant Dis. 87: 533-538.
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Progress 01/01/02 to 12/31/02
Outputs
A new Phytophthora resistance locus, Rps8, was mapped to MLG (major linkage group) A2 in two different crosses with PI399073. This is the first locus for Phytophthora resistance that has been identified on MLG A2. Partial resistance to Phytophthora sojae in soybean is expressed as a reduced level of root rot and is effective against all populations of the pathogen. Simple sequence repeat (SSR) markers were identified that are associated with putative quantitative trait loci (QTL) in the 'Conrad' which as partial resistance to P. sojae. Two putative QTLs donated by Conrad were identified in three populations and were positioned on soybean molecular linkage groups (MLG) F and D1b+W. The QTL on MLG F appears to be of more value based on the percent of genotypic variation explained. In collaboration with Dr. Scott Abney, USDA-ARS- Isolates of P. sojae representing races 1, 3, 4, 7 and 25 from IN and OH were compared on three separate sets of soybean differentials using
three separate seed sources. Races 1, 3, 4, 7, and 25 had the expected reaction on all three sets of differentials for Rps1b, Rps1c, Rps1k, Rps2, Rps3a,Rps4, Rps5, Rps7 and differentials Harlon, L59-731, and Union for Rps1a. Differentials L88-8470 for Rps1a and L93-3302 for Rps1d did not have the expected response. Additional races are needed to differentiate reactions on Rps3b, Rps3c, and Rps6. Utilizing different sources of resistance for Rps alleles may account for some of the differences in reactions among P. sojae isolates. The effects of temperature and soil moisture on infection and disease development by Rhizoctonia solani on soybean were studied individually. The temperatures evaluated in this study were not limiting to the isolates tested. In greenhouse studies, Root weights were greater and percent stand averages higher at 50 and 75% than at 25 or 100% MHC, however, as percent of control, the main effect on percent moisture for percent stand, plant height or root weight was
not significant. In both temperature and moisture studies, the R. solani isolates could be separated as predominantly causing 1) seed rot, as detected by greatly reduced plant stand; 2) root rot generally having no effect on plant stand but a high root rot rating and low root weight; or 3) hypocotyl lesions, having no effect on plant stand, a low root rot score and a high number of red lesions on the hypocotyl. In the greenhouse seed treatment evaluations of five fungicides, there was no fungicide by isolate interaction using these pathogenic types of R. solani. None of the seed treatments evaluated in this study provided 100% control of the four isolates tested. Due to the wide range of environmental factors that permit R. solani infection and disease on soybeans, other control measures that last all season such as host resistance, should be emphasized.
Impacts
A novel resistance gene to Phytophthora sojae has been identified and can now be introgressed with molecular markers into elite soybean germplasm to develop cultivars with resistance to P. sojae. In addition, loci which contribute to partial resistance to P. sojae have been identified and with marker-assisted selection, cultivars with both partial resistance and Rps genes can be developed. Differences in response among P. sojae isolates may be due to the differentials that were used. These studies begin to develop a standardized set of differentials to be used in the north central region.
Publications
- Burnham, K., Francis, D.M., Dorrance, A.E., Fioritto, R.J. and St.Martin, S.K. 2002. Genetic diversity among South Korean soybean plant introductions and other geographical populations. Crop Sci. 42: 338-343.
- Mueller, D.S., Dorrance, A.E., Derksen, R. C., Ozkan, E., Kurle, J.E., Grau, C.R., Gaska, J.M., Hartman, G.L., Bradley, C. A., and Pedersen, W.L. 2002. Efficacy of fungicides on Sclerotinia sclerotiorum and potential control of Sclerotinia stem rot on soybean. Plant Disease 86:26-31.
- Burnham, K.D., Dorrance, A.E., Francis, D.M., Fioritto, R.J. and St.Martin, S.K. 2003. A new locus in soybean for resistance to Phytophthora sojae. Crop Sci. 43:101-105.
- Dorrance, A.E., McClure, S.A. and deSilva, A. 2003. Pathogenic Diversity of Phytophthora sojae in Ohio soybean production fields. Plant Disease: in press. Dorrance, A.E., McClure, S.A. and St.Martin, S.K. 2003. Partial resistance to Phytophthora sojae in soybeans protects yield under high disease pressure. Plant Dis. In press.
- Dorrance, A.E., Kleinhenz, M.D., McClure, S.A. and Tuttle, N.T. 2003. Temperature, moisture and seed treatment effects on Rhizoctonia solani root rot of soybean. Plant Disease in press.
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Progress 01/01/01 to 12/31/01
Outputs
We have completed the survey of Phytophthora sojae pathotypes in Ohio. 72 races or pathotypes were identified among 429 P. sojae isolates collected from 84 locations and distinguished on the eight soybean differentials for Rps1a, Rps1b, Rps1c, Rps1d, Rps1k, Rps3a, Rps6 and Rps7. Sclerotinia stem rot is a major disease of soybean in the north central region. IN a 4-state study, we determined that under high disease pressure, no consistent control of Sclerotinia stem rot could be achieved with fungicides using different application systems. However, under moderate to low disease pressure, when fungicides penetrated the canopy, reduced the incidence of Sclerotinia stem rot an average of 50%. A 4 year field study which compared the reactions of 12 cultivars with different levels of partial resistance with and without Rps genes to diverse pathogen populations and disease pressure was completed. Yields from soybean cultivars with high levels of partial resistance ranked
significantly higher than those with low levels of partial resistance combined with an Rps gene when diverse populations of P. sojae were present. Soybean cultivars with specific resistance genes, Rps1k, Rps1k + Rps6, or Rps1k +Rps3a had higher yields than plants with only partial resistance in environments where race determination indicated that populations of P. sojae present were not capable of causing disease on plants with the Rps-1k gene. However, in an environment with very low disease pressure, yields of soybean varieties with partial resistance were not significantly different from those with single Rps genes or Rps gene combinations. These results demonstrate that genetic traits associated with high levels of partial resistance do not have a negative effect on yield. 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. Extracts were tested for BPMV and SMV by ELISA. These results indicate that both BPMV and SMV were present in the samples in 1999 but only BPMV in 2000.
Impacts
Recommendations can now be made to plant breeders on the best Rps gene combinations to deploy in new soybean cultivars targeted for Ohio Producers. We have clearly demonstrated that partial resistance to Phytophthora sojae does not have a negative impact on yield, breeders can begin to incorporate this durable form of resistance in varieties targeted for Ohio to prevent widespread losses Fungicide applications which can penetrate soybean canopies may help reduce the incidence of Sclerotinia stem rot under low to moderate disease pressure. Bean Pod Mottle Virus may be a major cause of seed mottling in Ohio. Disease management strategies which reduce the impact of this virus can now be saught.
Publications
- Dorrance, A.E. and McClure, S.A. 2001. Beneficial effects of fungicide seed treatments for soybean cultivars with partial resistance to Phytophthora sojae. Plant Dis. 85:1063-1068.
- Dorrance, A.E., Gordon, D.T., Schmitthenner, A.F., and Grau, C.G. 2001. First report of bean pod mottle virus in soybean in Ohio. Plant Disease 85:1029.
- Dorrance, A.E., Inglis, D.A., Helgeson, J.P. and Brown, C.R. 2001. Partial Resistance to Phytophthora infestans in Four Solanum Populations. Am. J. of Potato Res. 78:9-17.
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Progress 01/01/00 to 12/31/00
Outputs
The plant age when partial resistance and Rps genes are effective against P. sojae was determined in a greenhouse assay. Soybean seeds and seedlings with high levels of partial resistance were susceptible to infection by P. sojae while the cultivar with an Rps gene was resistant. The variety with partial resistance, stand reductions and high levels of root rot occurred for soybean seeds until the unifoliates were present. P. sojae was recovered with the soybean cultivar, Resnik (Rps-1k)from 60 percent of 86 locations sampled in Ohio. This may explain the high percentage of fields that required replanting during the spring of 2000 as well as the reduced stands and shorter plants in many production regions. Twenty-nine of the isolates collected in this study were subjected to cellulose-acetate electrophoresis and virulence pathotyping. Seven isozymes namely, glucose-6-phosphate isomerase, isocitrate dehydrogenase, malic dehydrogenase, 6-phosphogluconate dehydrogenase,
fumarate hydratase, acontitate hydratase, and glucose-6-phosphate dehydrogenase (G6PDH) were resolved. Only G6PDH could not be resolved with the cellulose acetate system. There was no isozyme variation among these isolates in this study. Two to three virulence pathotypes were identified from each of the six fields. Fungicide application techniques for management of Sclerotinia stem rot were evaluated in a field with a history of white mold. Fungicide was applied to plots with conventional or an air assist type sprayer. There was an average of 53.7 percent Sclerotinia stem rot in all of the plots and all of these plants had lesions on the main stem. This is due to the extended period of fog that occurred in this plot during the growing season. Greenhouse and growth chamber studies were used to compare disease development among eight Rhizoctonia solani isolates collected in Ohio at four levels of soil moisture holding capacity (25, 50, 75 and 100 percent MHC) and four temperatures (20,
25, 30, 35 C). Levels of aggressivness and disease symptoms varied among the isolates. Hypocotyl, root and seed rot were caused by 5, 2, and 1 of the R. solani isolates evaluated, respectively. All isolates were capable of causing disease at all moisture levels and temperatures tested and there was not one moisture or temperature that had significantly higher disease levels for all of the isolates. Two inoculum application methods, R. solani-colonized oats applied in the furrow at planting and on the soil surface, were compared in field trials. To determine if treatment effects could be measured, soybean seed treated with fludioxonil and untreated were used. Soil surface inoculum application methods reduced stand but did not affect yields in both studies. The in-furrow inoculum application at a rate of 12.5 ml per plot (4, 25ft rows) provided the most consistent level of disease among those tested in both years of the study.
Impacts
Fungicide seed treatment on cultivars with partial resistance may be beneficial when the environmental conditions that favor P. sojae infections occur prior to soybean emergence which will improve soybean stands. Rhizoctonia solani can infect soybean plants across a wide range of moisture levels and temperatures. This will greatly enhance development and evaluation of greenhouse assays for germplasm evaluation as well as fungicide efficacy tests.
Publications
- Tuttle, N. 2000. Characterization of Environmental Conditions Conducive to Rhizoctonia solani Infections in Soybean, and Evaluation of Inoculum Application and Density In Field Studies. M.S. Thesis. The Ohio State University 70pp.
- Dorrance, A.E. and Schmitthenner, A.F. 2000. New sources of resistance to Phytophthora sojae in the soybean plant introductions. Plant Dis. 84:1303-1308.
- Dorrance, A. E., McClure, S. A., and Tuttle, N. 2000. Evaluation of fungicides for control of Rhizoctonia seedling diseases in soybeans under drought conditions, 1999. Fungicide and Nematicide Tests 55:460.
- Dorrance, A.E. and McClure, S. A. 2000. Evaluation of seed treatment fungicides for control of Phytophthora root rot in soybeans, 1999. Fungicide and Nematicide Tests 55:459.
- DeSilva, A., McClure, S. and Dorrance, A. 2000. Use of cellulose acetate electrophoresis to determine isozyme variations in Phytophthora sojae. Phytopathology 90:S18.
- Tuttle, N. and Dorrance, A.E. 2000. Comparison of Rhizoctonia solani inoculum application methods and densities in soybean. Phytopathology 90:S78.
- Dorrance, A.E. and St.Martin, S.K. 2000. Phytophthora sojae, Is it time for a new approach. Phytopathology 90:S93.
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