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Display category headings
Research Project:
Characterization of Aluminum and Heat Tolerance in Soybean Plant Introductions and Breeding Lines
Location:
Soybean and Nitrogen Fixation Research
2000 Annual Report
1. What major problem or issue is being resolved and how are you resolving it?
August drought is the greatest threat to profitability in soybean today. Too often a crop with great promise ends up with only fair or poor yields because of dry weather. Our long-term objective is to solve this problem through the delivery of high-yielding drought-tolerant varieties to U.S. farmers. The potential for success is great. Yet, no progress has been made in this area to date. The reason is that drought tolerance breeding is complex and high risk. Most of the 120 U.S. soybean breeders are unprepared for this task and unable to stay the course long enough to achieve success. The project provides the only success story in the area of drought tolerance breeding in soybean in the USA.
2. How serious is the problem? Why does it matter?
August drought is Public Enemy No. 1 when it comes to soybean profitability. There is no chemical to spray, no variety to select, and no crop rotation to follow which mitigates the impact of drought. Severe stress occurs every two to four years on the farm, with intermediate stress levels occurring every other year. In economic terms, a modest 5 bushel per acre increase for U.S. production in a dry year (a goal achievable by this project) translates to an extra 350 million bushels and $2.1 billion in extra farm sales (if one assumes a price of $6 per bushel).
3. How does it relate to the national Program(s) and National Program Component(s) to which it has been assigned?
Farm prices for soybean have fallen to 25-year lows, and most soybean growers are producing soybean at a net loss. This project will help restore the nations' profitability in soy production. Economic analyses show that soybean prices are likely to remain low, primarily because Brazil and Argentina now provide a flood of cheaply-produced foreign beans in the global market place. In the past, U.S. agriculture countered this foreign competition through the steady release and deployment of new and more profitable cultivars. Comparable R&D; in Latin America was lacking. However, practical breeding in Brazil and Argentina is now well funded and this competitive edge has been lost to the U.S. The project will restore the U.S. edge in profitability through new and innovative breeding approaches. The primary route is to improve abiotic stress tolerance in U.S. soybean varieties. Although most of the 120 U.S. soybean breeders recognize abiotic stress as an important issue, few are able to actively pursue this genetic research area in soybean. This project provides leadership to scientific teams, the larger scientific community, commodity groups, and private industry in the areas of abiotic stress. This project also contributes genetic resources to help solve the problem of abiotic stress.
4. What was your most significant accomplishment this past year?
A. Single Most Significant Accomplishment during FY2000 year: No commercially usable drought tolerant soybean varieties have ever been released to the U.S. farmer. To facilitate development of such varieties, the project has continued to expand its efforts to better identify root characteristics that are associated with drought tolerance. Four genes which impart Al tolerance to soybean roots were identified. B. Other significant accomplishment(s): Currently, we are developing new methods for imaging roots in soil. The methodology involves 'magnetic resonance imaging' (MRI), and is being completed in cooperation with scientists at the Duke University Medical School. Using young plants grown in containers and soil cores from field grown plants, we are attempting to characterize root morphological features that contribute to efficient water uptake. Experiments will include imaging roots that encounter a hard pan and zones of high Al, to determine how root morphology is modified in the presence of stress. The method holds great promise in helping to identify and harness root characters responsible for drought stress tolerance. We are also continuing a search for genetic heat tolerance. Our initial four experiments indicated that higher temperatures increased plant height and the number and area of main stem leaves while decreasing the number and area of leaves on branches. Genetic differences were also observed in specific leaf weight (SLW) in response to temperature treatment. The Plant Introduction (PI) N92-SH 447 declined in SLW as the temperature increased, while the opposite was true of other lines (N92-SH 580, PI 416937). Specific leaf weight is the measure of leaf weight per unit area and is related to the amount photosynthetic machinery per unit area of leaf. SLW is often related to higher photosynthesis rates per unit area. Different patterns of change in SLW among these lines may be important indicators of tolerance or susceptibility to high temperatures. We hope to determine if the observed genetic differences are meaningful in terms of plant performance. Recent experiments showed that soybean plants maintained photosynthetic rates for temperature regimes ranging from 28 to 40 degrees C during the day, suggesting that normal cellular functions were not disrupted by high temperatures, although biomass was decreased at the highest temperatures. Surprisingly, no seed set was observed for any genetic type when grown at 40 degrees C. This suggests that seed set is more sensitive to heat stress than plant growth per se. We are currently preparing for harvest of our latest phytotron experiment which includes an analysis of the number of pollen grains produced and their germination at various temperatures. Data of pollen grain production and germination will clarify the effects of high temperature stress on the male reproductive development. Microscopic analysis of various stages of flower formation will also be completed to help elucidate the effects of high temperature stress on pollen release and development. C. Significant Accomplishments that Support Special Target Populations: Products of this work will assist small farms. Drought tolerant varieties will cost no more to grow than normal varieties or require any extra input. Higher yields derived from them will increase profitability.
5. Describe your major accomplishments over the life of the project, including their predicted or actual impact?
Molecular tagging identified four new genes which impart Al tolerance to soybean roots.
6. What do you expect to accomplish during the next year?
Objectives that should be achieved in the next year include: Continue DNA tagging of Al tolerance genes in soybean roots, continue refinement of root imaging techniques, continue screening for heat tolerant soybean germplasm.
7. What technologies have been transferred and to whom? When is the technology likely to become available to the end user (industry, farmer other scientist)? What are the constraints, if known, to the adoption durability of the technology?
Information is transferred to other scientists through publications and presentations at meetings. Descriptions and illustrations of technologies have been shared in reports to the United Soybean Board. Advanced germplasm is being shared, for hybridization and variety development purposes, with four major private soybean breeding enterprises. One variety was release this year. Other varieties and germplasm will be released over the next two years.
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