Progress 08/01/06 to 07/31/09
Outputs
OUTPUTS: Soybean cyst nematode suppressed US soybean yields 93.98 million bushels during 2007. Soybean cyst nematode suppressed US soybean yields more than any other disease each year since 1996. The University of Missouri SCN Research Team developed a productive early group V conventional soybean lines, S05-11268, that has broad resistance to SCN HG types or races. This line has shown resistance to SCN races 1, 2, 3, 5, and 14 and also shows resistance to reniform nematode Rotylenchulus reniformis. Yields of this line have been equal to a popular group V Roundup Ready cultivar from Monsanto. We increased seed of three lines that are resistant to SCN with resistance to roundup; SS02-292, SS02-662, and SS02-3770. Maturities of these lines range from late III to early IV. Each also has resistance to Phytophthora root rot. These lines are ready for release. We determined that H. glycines uses molecular mimicry of plant CLE peptide signals as a mechanism for plant parasitism. This is a remarkable adaptation by an animal to developmentally reprogram host plant cells for its own parasitic advantage. The functional conservation of H. glycines and plant CLE proteins is restricted to the C-terminal CLE motif. However, sequences outside the CLE motif are also required for nematode CLE function in planta and were found to have dual roles in cellular targeting and host-specific recognition of nematode CLE proteins. What specifies H. glycines host range and whether there is a genetic basis for this host specificity is not known. Thus, host-specific H. glycines CLE peptide recognition may help explain the molecular mechanism controlling host-range specificity of H. glycines. Moreover, a correlation between the presence of specific CLE sequences in H. glycines populations correlates with their ability to reproduce on resistant soybean germplasm, suggesting that H. glycines may be using CLE peptide mimicry as a mechanism for virulence. These results were recently submitted to The Plant Cell for review. We have developed F7 recombinant inbred lines (RILs) derived from the Magellan x PI 438489B (Pop 1) and Magellan x PI 567516C (Pop 2) populations. These RILs populations were employed to confirm the novelty of the new QTL previously identified in the F2:3 lines of these two crosses. Molecular and QTL analysis showed three novel QTL associated with resistance to multi-HG Types of SCN that mapped on Chromosome 4 (LG C1) in Pop1, and Chromosomes 10 (LG O) and 18 (LG G) in Pop 2. One of our greatest recent accomplishments was the development of SS97-6946 which has resistance to all major races of the soybean cyst nematode and the broad-spectrum resistance is from a PI other than the Hartwig source, PI 437654. SS97-6946 is in an early IV background and is being used by most of the soybean companies in the US. PARTICIPANTS: The project investigators were Dr. Melissa Mitchum, Dr. Henry Nguyen, Dr. Dave Sleper, Dr. Grover Shannon, and Dr. Allen Wrather, and all are faculty in the University of Missouri Division of Plant Sciences. Each work with scientists at other universities, but the funding from this source was for in house projects only. Training or professional development were not provided as part of this project. TARGET AUDIENCES: The results of the research from this project will be of use to university and private industry scientists, crop consultants, and extension personnel around the United States. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Soybean cyst nematode (SCN), Heterodera glycines, has been and remains the most serious pest to soybeans in the United States. The ecological adaptability of this nematode is such that it can apparently thrive and damage soybean wherever this host can be cultivated, a statement that cannot be made for any other soybean pathogen. Presently, about 80% of the US farmland planted to soybean is infested with soybean cyst nematode. In 2007, US soybean producers nationally lost an estimated $751.8 million (93.98 million bushels at $8/bu) due to this pest. Scientists in Arkansas, Delaware, Georgia, Illinois, Indiana, Iowa, Kentucky, Maryland, Michigan, Minnesota, Missouri, North Carolina, Tennessee, and Virginia view SCN as their soybean farmers' worst enemy. The SCN-soybean interaction is extremely complex. New varieties must continually be developed as the nematode adapts to older ones. Since 2000, The University of Missouri SCN Research Team has developed 19 soybean varieties with resistance to SCN, developed and released 8 soybean breeding lines resistant to SCN, and identified 118 soybean lines that have SCN resistance from the world collection of about 16,000 lines. The genes responsible for SCN resistance in two wild soybean lines commonly used as parents when developing high yielding SCN resistant soybean cultivars have been mapped (finger printed) by the University of Missouri team using molecular methods. This discovery will greatly enhance use of these lines in developing SCN resistant varieties by all soybean breeders in the USA. The benefits from this research are being realized in Missouri and all other states where SCN reduces soybean yield. In Missouri alone, this research has resulted in $50 million greater farm profits per year since 1999.
Publications
- Wang, J., Replogle, A., Joshi, S., Korkin, D., Hussey, R., Baum, T.J., Davis, E.L., Wang, X., and Mitchum, M.G. 2009. Nematode CLE Peptide Mimicry: Dual Roles for the Variable Domain in Cellular Targeting and Host-Specific Recognition of Nematode CLE Proteins. The Plant Cell (submitted).
- Mitchum, M.G., X. Wang, and E.L. Davis. 2008. Diverse and conserved roles of CLE peptides. Current Opinion in Plant Biology 11:75-81. *Invited review article.
- Wu, X., Blake, S., Sleper, D.A., Shannon, J.G., Cregan, P., and Nguyen, H.T. 2008. QTL, Additive and Epistatic Effects for SCN Resistance in PI 437654. Theory and Applied Genetics. (accepted).
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Progress 08/01/07 to 07/31/08
Outputs
OUTPUTS: Germplasm line S02-2259 was recently released. It is a late group 5 maturity and was released to breeders for use in crossing for soybean improvement. It is resistant to SCN HG type 0 (race 3) based on greenhouse tests at Portageville and Columbia, MO. S02-2259 is also resistant to stem canker, bacterial pustule and some races of frogeye leaf spot. Two F2:3 populations derived from the Magellan x PI438489B and Magellan x PI567516C crosses were genotyped with 250 SSR and 20 SNP markers to confirm putative QTL and identify novel QTL/genes. In the Magellan x PI438489B population, we have identified and mapped two known QTLs (rhg1 and Rhg4 loci) on LG G and A2. In addition, we also mapped putative QTLs on LG C1, J, and K. We are currently utilizing F7 recombinant inbred line (RIL) of this population to confirm mapped QTLs and develop near-isogenic lines (NILs) for fine-mapping and positional cloning. For the Magellan x PI567516C population, phenotyping assay was completed and genotyping is in progress. We anticipate data collection and QTL analysis will be completed early 2008. Subsequently, QTL confirmation study will be conducted using F7 RIL population. We screened ~50 parental lines and genotyped over 22,000 samples submitted for SCN breeding programs. In addition to routinely used SSR markers, ~20 SNP markers particularly developed for the two major resistance loci, rhg1 and Rhg4, were also surveyed for polymorphisms and validated. PARTICIPANTS: Dr. Melissa G. Mitchum, Assistant Professor, Division of Plant Sciences, Columbia. Her SCN research is focused on the mechanism and genetics of SCN virulence. Dr. Henry T. Nguyen, Professor, Division of Plant Sciences, Columbia. His SCN research is focused on marker assisted selection to screen for SCN resistance and the SSR diversity among soybean cultivars for resistance to SCN. Dr. J. Grover Shannon, Professor, Division of Plant Sciences, Portageville. His SCN research is focused on developing high yield group IV and V SCN-resistant soybean lines and cultivars and assist with marker assisted selection to screen for SCN resistance and the SSR diversity among soybean cultivars for resistance SCN projects. Dr. David A. Sleper, Professor, Division of Plant Sciences, Columbia. His SCN research is focused on developing improved soybean lines and cultivars with SCN resistance for north Missouri and assist with marker assisted selection to screen for SCN resistance and the SSR diversity among soybean cultivars for resistance SCN. Dr. J. Allen Wrather, Professor, Division of Plant Sciences, Portageville. His research is focused on determining the impact of SCN on soybean production in the U.S, and the distribution and virulence biotypes of SCN in Missouri. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Soybean cyst nematode suppressed US soybean yields 136.7 million bushels during 2004 and 123.8 million bushels during 2006. This pest suppressed US soybean yields more than any other disease each year since 1996. SCN management is possible but not complete with crop rotation. Resistant cultivars must be planted. We released one germplasm line during 2007, S02-2259, that is resistant to some races of SCN and also stem canker and some races of Cercospora sojina. It will be useful as a parent because it combines high yield potential and disease resistance with 25% of its pedigree derived from plant introductions that are not known to be present in the current gene pool for cultivar development in the southern USA. We continue to search for SCN resistant genes. In the Magellan x PI438489B population, we identified and mapped two known QTLs (rhg1 and Rhg4 loci) on LG G and A2. In addition, we mapped putative QTLs on LG C1, J, and K. We are now searching for parasitism genes in SCN. Intraspecific comparative genomic studies have confirmed the presence of two H. glycines CLAVATA3/ESR (CLE)-related genes (HgCleA and HgCleB) that are expressed in parasitic life stages. These genes encode secreted products that may function as ligand mimics to promote parasitism and their role as virulence factors is being assessed in this project. Both HgCleA and HgCleB have been expressed in soybean hairy roots to characterize their effects on root growth. Through these studies we have optimized the soybean hairy root system which is now enabling us to assess a role for HgCleB in virulence by expressing this gene in resistant soybean and infecting with an avirulent population of SCN. In addition, we have initiated the development of Agrobacterium-based infiltration studies as another approach to assess the role of HgCLEs in SCN virulence of resistant soybean. Much of this information has been distributed to the public in scientific publications and in University of Missouri Extension publications.
Publications
- Ithal, N., J. Recknor, D. Nettleton, T. Maier, T.J. Baum, M.G. Mitchum. 2007. Developmental transcript profiling of cyst nematode feeding cells in soybean. Mol. Plant-Microbe Interact. 20(5): 510-525.
- Mitchum, M.G., J.A. Wrather, R. D. Heinz, J.G. Shannon, and G. Danekas. 2007. Variability in distribution and virulence phenotypes of Heterodera glycines in Missouri during 2005. Plant Disease 91:1473-1476.
- Replogle, A., J. Wang, X. Wang, E.L. Davis, and M.G. Mitchum. 2007. Phenotypic characterization of roots responding to Heterodera glycines CLE peptides. Phytopathology 97 (7): S98.
- Shannon, J.G., J.A. Wrather, J.D. Lee, D.A. Sleper and S.C. Anand. 2007. Registration of S02-2259 soybean germplasm line. Journal of Crop Registrations 1: 68-69.
- Shannon, J.G., J.A. Wrather, J.D. Lee, D.A. Sleper and S.C. Anand. 2007. Registration of S01-9364 and S01-9391 soybean germplasm resistant to soybean cyst nematode with seed oil low in linolenic acid. Journal of Crop Registrations 1:164-165.
- Shannon, J.G., J.A. Wrather, D.A. Sleper, H.T. Nguyen, and S.C. Anand. 2007. Registration of Stoddard soybean. Journal of Crop Registrations 1: 28-29.
- Shannon, J.G., J.A. Wrather, D.A. Sleper, R.T. Robbins, H.T. Nguyen, and S. Anand. 2007. Registration of Jake soybean. Journal of Crop Registrations 1: 29-30.
- Wang, X., A. Replogle, E.L. Davis, and M.G. Mitchum. 2007. The tobacco Cel7 gene promoter is auxin-responsive and locally induced in nematode feeding sites of heterologous plants. Molecular Plant Pathology 8(4): 423-436.
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Progress 08/01/06 to 08/01/07
Outputs
We released three soybean lines during 2006; SS00-11741, S01-9364, and S01-9391. SS00-11741, MG mid IV, has shown resistance to SCN HG type 0 (race 3) based on greenhouse tests in Columbia, MO with a female index of 7, versus 73 for the susceptible check. It has also shown resistance to races 1, 3 and 4 of Phytophthora root rot, and it is resistant to glyphosate. It has a very high protein content of 44.4% on a dry matter basis. S01-9364 and S01-9391, both MG late V, have resistance to H. glycines populations and resistance to root knot nematode with 3 to 4 % linolenic acid in seed oil to improve food flavor, shelf life and cooking stability. We released Stoddard, MG late IV, and Jake, MG mid V, in 2006. They are new conventional soybean cultivars that have broad resistance to SCN populations and resistance to root knot nematode and reniform nematode. We determined inheritance of SCN resistance to race 1 and 5, and races 3, 5 and 14 in PI 507354 and PI 467312,
respectively. Inheritance in 507354 was conditioned by four genes (one dominant and three recessive genes). Inheritance in PI 467312 was conditioned by 3 genes; one dominant and 3 recessive genes for races 3 and 5; and three recessive genes for resistance to race 14. We previously identified two forms of Heterodera glycines CLAVATA3/ESR (CLE)-related genes (HgCLEA and HgCLEB) that were expressed in parasitic life stages. These genes encode secreted products that may play a role in ligand mimicry for parasitism and function as virulence factors. The genes are not expressed in non-feeding life stages. Restriction fragment length polymorphism (RFLP) analysis on products amplified from cDNA generated from 15 inbred lines determined that HgCLEA is found in all nematode populations, however, the presence of both HgCLEA and HgCLEB showed a correlation with the ability of the nematode to parasitize almost all resistant soybean germplasm (i.e. was found in only a subset of populations that
were highly virulent on resistant soybean). To study the correlation of HgCLEB with SCN virulence on resistant soybean we developed a genotyping assay that would allow us to follow these genes in the progeny of individual nematodes of controlled crosses between SCN inbred lines. We conducted a controlled cross between Heterodera glycines PA3 (only has HgCLEA) and TN19 (has both HgCLEA and HgCLEB) using a backcross 1 F2 (BC1F2-derived) crossing strategy. Using our genotyping assay, we have identified virgin females that are AA and AB, but not BB which suggests that HgCLEA is required for parasitism and HgCLEB is not sufficient for parasitism. The populations have been amplified and subjected to host-range testing to look for correlations with virulence on resistant soybean lines
Impacts
SCN management is possible with crop rotation but is best accomplished by planting SCN resistant cultivars. We released one soybean cultivar and three soybean lines that are resistant to SCN and other diseases. We continue to search for SCN resistant genes.Inheritance in 507354 was conditioned by four genes (one dominant and three recessive genes). Inheritance in PI 467312 was conditioned by 3 genes; one dominant and 3 recessive genes for races 3 and 5; and three recessive genes for resistance to race 14. We are now searching for parasitism genes in SCN.Using our genotyping assay, we have identified virgin females that are AA and AB, but not BB which suggests that HgCLEA is required for parasitism and HgCLEB is not sufficient for parasitism.
Publications
- Ithal, N., J. Recknor, D. Nettleton, L. Hearne, T. Maier, T.J. Baum, M.G. Mitchum. 2007. Parallel genome-wide expression profiling of host and pathogen during soybean cyst nematode infection of soybean. Mol. Plant-Microbe Interact. (in press).
- Wang, J., A. Replogle, X. Wang, E.L. Davis, and M.G. Mitchum. 2006. Functional analysis of nematode secreted CLAVATA3/ESR (CLE)-like peptides of the Genus Heterodera. Phytopathology 96:S120.
- Guo, B., D.A. Sleper, H.T. Nguyen, P.R. Arelli, and J.G. Shannon. 2006. Quantitative trait loci underlying resistance to three soybean cyst nematode populations in soybean PI 404198A. Crop Sci. 46:224-233.
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