Soybean Research Illinois-Soybean Disease Biotechnology Center

NON-TECHNICAL SUMMARY: Soybean diseases cause significant losses to the U.S. soybean crop every year. The overall purpose of the Center is to employ novel strategies and technologies to the current and pending agricultural plant disease problems in the U.S. and to contribute to the reduction of yield losses due to the major soybean diseases.

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APPROACH: For objective number one, wide hybridization will utilize germplasm from wild annual and perennial Glycine spp. which have shown resistance to soybean rust, soybean cyst nematode, and bean pod mottle virus. For the second objective, nanotechnology enhancement will include a pilot program to promote active learning, seminars, and workshops that will facilitate collaboration among Center researchers and leading experts in nanotechnology from around the world. For the third objective, strategic and analytical tools will be developed to inform public and private decision makers regarding the impact of risk and uncertainty associated with biotechnological change. For objective four, research findings generated by the Center will be made available to soybean producers through a powerful web-based system, the Varietal Information Program for Soybeans (VIPS).
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PROGRESS: 2004/07 TO 2007/07 <BR>
Progress for seven distinct projects is reported at this time. For wide hybridization efforts to diversify the soybean genome, Glycine tomentella, which is resistant to soybean rust, soybean aphid and soybean cyst nematode was used. Since the initial wide hybridization event, twenty-one BC2 plants with 60 chromosomes have been produced, and eight of the 21 BC2 plants are resistant to soybean rust. Progeny of BC2 plants resistant to soybean rust produced 24 BC3 plants with chromosome numbers ranging from 2n=41-49. In testing endogenous soybean compounds produced in seed coats of dark-pigmented soybean seed varieties for their effect on soybean rust spores, the dark pigmented proanthocyanidins were extracted from the black seed coats, and soybean oligo arrays were produced and will be used to examine gene expression changes. To investigate the genetic structure and diversity of expanding soybean rust (Phakopsora pachyrhizi) populations, isolates were collected from soybean and kudzu in Florida, other U.S. states, and other continents and at different time intervals. DNA was extracted and preliminary experiments begun to explore the role of structure in molecular evolution and genetic diversity of the fungus. A protocol was developed for Affymetrix gene chip mapping in soybean that outperforms all currently available methods of this type. The method was used successfully to discover SNP markers linked within 1 centimorgan of the aphid resistance gene Rag1, and also to find closely linked markers to a soybean rust resistance gene, Rpp1. The technology is being further developed and applied to additional soybean genes. To design soybean cyst nematode (SCN) genotyping assays, random genomic sequence data collected from two inbred SCN lines (one virulent and one avirulent type) was used, and over 6,806 putative single-nucleotide polymorphisms (SNPs) have been discovered. Experiments were completed to more accurately map the aphid resistance gene Rag1 from Dowling. To do this, approximately 2,000 F2 plants segregating for Rag1 were tested with markers and those plants with recombination near the gene were selected and tested for aphid resistance. This research allowed us to reduce the interval that we know the gene maps by 7 map units. Eighty plant introductions (PIs) with putative aphid resistance were retested with two different aphid isolates, and this list has been reduced to 43 PIs with confirmed resistance. The comparative cytotoxicity of five soybean rust fungicides currently allowed by the U.S. EPA was assayed using Chinese hamster ovary cells and a standard toxicity assay. The rank order of fungicides for decreasing toxicity was trifloxystrobin > tetraconazole > propiconazole > tebuconazole > myclobutanil. In addition, two fungicides were evaluated for their genomic DNA damage activity. Myclobutanil in a concentration range from 100 to 1,000 micrometers was not genotoxic. Tetraconazole gave conflicting results in a concentration range of 100 to 325 micrometers.
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IMPACT: 2004/07 TO 2007/07 <BR>
These impact statements are for seven different projects. Wide hybridization between soybean and Glycine tomentella will produce soybean lines containing unique genes not currently available in the soybean gene pool and resistant to soybean rust, soybean aphid, and soybean cyst nematode. Compounds in black-seeded soybeans may deter the progression of infection by fungal pathogens including Phakopsora pachyrhizi, the causal agent of Asian soybean rust. A collection of fungal genetic material is fundamental to the study of the genetic diversity, biogeography, and molecular ecology of the soybean rust fungus. The Affymetrix method provides a quick and informative method of genetic mapping that can be applied in many soybean cultivars where few genetic markers are available. When the mechanism by which SCN adapts and grows on resistant soybean is understood and SCN virulence genes are identified, then the soybean resistant sources could be effectively rotated to protect the long term usefulness of valuable SCN resistant soybean varieties. Soybean genetic mapping work will allow researchers to increase their efficiency of marker-assisted selection for aphid resistance and facilitate the identification and deployment of new sources of aphid resistance. The fungicide toxicity assay is the first study to show the distribution of toxicity of fungicides used to manage soybean rust, and the goal is to identify the most effective anti-rust fungicide that poses the lowest risk to public health and the environment.