Location: Crop Genetics Research2011 Annual Report
1a. Objectives (from AD-416)
1. Develop high yielding soybean germplasm with enhanced seed composition and plant protection traits for soybean production system of the mid-south United States; 2. Identify the physiological mechanisms that regulate seed composition qualities of oil, fatty acids, and protein under stress environment; 3. Optimize Early Soybean Production Systems (ESPS) and pest management strategies for the mid-south United States; and 4. Coordinate and participate in the Uniform Soybean Test - Southern States.
1b. Approach (from AD-416)
Use publicly available genetic diversity in soybean germplasm, including fatty acid mutants, phytic acid mutants and Plant Introductions from USDA collections, to develop germplasm with modified fatty acid and phytic acid levels which are adapted to the mid-south; use publicly available genetic diversity and known charcoal rot resistant lines to improve charcoal rot resistance in germplasm with high yield potential for the mid-south; develop high-yielding agronomically superior lines with adaptation to Early Soybean Production System (ESPS) using available genetic diversity from both northern and southern USA lines; determine the effects of nutrient uptake and assimilation on oil, fatty acids, and protein production in seed under drought; measure the effects of drought and heat stress on nutrient uptake and assimilation on oil, fatty acids, and protein production in seed; determine optimum plant density and row spacing for cultivars of different maturities and plant architecture adapted to ESPS for yield or fungicide deposition; relate optimum population to light interception; determine optimum seeding rate for late plantings; evaluate planting date effect on soybean rust infection; determine effect of late season insecticide application on yield; coordinate, analyze data, and publish the annual reports of the Uniform Soybean Tests – Southern States.
3. Progress Report
Crosses were sucessfully made to introgress high oleic acid, low phytic acid, and Asian Soybean Rust resistance traits into soybean adapted to the mid-south. Second generation crosses to bring earliness into southern germplasm from northern soybean lines were moderately successful. Yield crosses were successful. Crosses were advanced to F2 generation. Low linolenic acid lines (<2.55%) were advanced, and BC1F2 and F2 populations were screened with molecular marker to identify low linolenic and normal linolenic lines. The mid-oleic (elite parent) plant rows were sucessfully evaluated for agronomics, maturity and fatty acid concentration. Selections were made that will be used for field trials to evaluate the effect of maturity on seed composition. Work to use Plant Introductions (PI) to increase oleic acid showed that F5 single plant selections from normal oleic acid lines crossed to PI lines had elevated oleic acid. Charcoal rot screening in an inoculated nursery was less than successful due to drought in the non-irrigated nursery, but selections were made based on survival and agronomics. Lines that have low phytic acid were grown and re-evaluated for low phytate and agronomics. A new improved source of the low phytate trait was used for crosses. BC1F2 and F2 plants were screened with markers in the low phytate genes. Asian soybean rust screening in Paraguay found highly resistant lines which need to be retested. This was the final year of crosses and six successful crosses were made to a Plant Introduction that has resistance in Mississippi. The program to combine rust gene Rpp1b with either Rpp2 or Rpp4 resistance genes has 4 surviving populations of BC1F5:6 lines from 3 crosses. Four BC1F5 and one F5 population were single planted to make lines for testing. Our soybean line DB04-10836 ranked #1 for overall yield in the summary of 2-year yields for Maturity Group V Conventional Tests for the 2009 and 2010 Mississippi Soybean Variety Trials. It will be advanced to a third year in the Uniform Soybean Tests. Work on the Uniform Soybean Tests – Southern States continues. Research continues to understand the physiological traits that significantly impact seed composition (protein, oil, fatty acids, sugars, and minerals) in soybean under drought, heat, and chemical stress conditions. Data obtained from greenhouse and field experiments were analyzed in 2010-2011. The effect of temperature and maturity on seed sugars and mineral nutrition in near-isogenic lines for maturity genes were examined. Results showed that the contribution of temperature, maturity, and genetic background depends on the type of sugar and mineral. Mechanisms of drought tolerance using slow-wilting trait in soybean gemplasm obtained from USDA-ARS, Raleigh, NC, are being investigated. This experiment is still underway through 2012. The effect of phomopsis on soybean seed protein, oil, fatty acid, sugars, and mineral nutrition in phomopsis susceptible, moderately resistant, and resistant lines was investigated and a manuscript is in preparation for submission.
1. Distribution of soybean seed protein, oil, and fatty acids along soybean stem. Generally, improving seed composition quality of protein, oil, or fatty acids has been based on whole-plant seed selection either as a single plant or as a group of plants (bulk selection). Selecting seed quality using this approach may not be efficient if seed quality differs along the soybean stem from top to bottom. Therefore, variability and distribution of seed protein, oil, and fatty acids were investigated in different soybean varieties at the top and bottom of the soybean canopy. Seed protein, oil, and fatty acids significantly varied, depending on the position of the seed on the main stem. Generally, higher protein and oleic acids were found at the top nodes, but higher oil and linolenic acid were found at the bottom. This research helps breeders to select for seed composition qualities more efficiently by using single seed selection rather than bulk selection.
2. Quantifying maturity genes and temperature effects on soybean seed sugars and minerals. Understanding the interaction between the environmental factors (such as temperature) and soybean maturity genes for seed constituents (sugars and minerals) is important for stability of these constituents. Therefore, a field experiment was conducted to quantify the effects of temperature, maturity, and genetic background on seed sugars and mineral nutrition in near-isogenic lines for maturity genes (isolines are soybean lines derived from a common ancestor, therefore they have the same genetic background, but each line differs from the other in one or more known gene, in this case genes for maturity). The contribution of temperature, maturity, and genetic background to the stability of the constituents depends on the type of mineral nutrient and sugar (sucrose, raffinose, or stachyose). This information will help breeders develop soybean germplasm with higher mineral seed content, and to more efficiently select for seed sugars.
Ding, W., Reddy, K.N., Zablotowicz, R.M., Bellaloui, N., Bruns, H.A. 2011. Physiological responses of glyphosate-resistant and glyphosate-sensitive soybean to aminomethylphosphonic acid, a metabolite of glyphosate. Chemosphere. 83:593-598.