2009 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.
Crosses to introgress low linolenic acid, mid oleic acid and low phytic acid traits into soybean adapted to the Mid South region were successfully made. In most cases, sufficient seed was obtained to proceed with experiments. Simple probe markers for low linolenic acid were validated in the breeding material and two BC1F1 (hybrids) plants were identified as double heterozygous for the markers, and populations from these plants will be grown in the field in 2009 and screened for the markers. Lines with greater than 45% oleic acid and lines with low to normal oleic acid are being evaluated. A program to pyramid the rust resistance genes Rpp1b with the Rpp2 and Rpp4 resistance genes from Williams soybean was begun. Four populations were identified as potentially containing two rust resistance genes. Two breeding lines with resistance to soybean cyst nematode were advanced to the Uniform tests from the Preliminary tests. The project received request for seed of lines that performed well in the 2007 Arkansas variety tests. Research on understanding the physiological traits that significantly impact seed composition and yield when soybean is grown under drought and heat stress or with infected with diseases of charcoal rot and Phomopsis seed decay. Effects of chemical stresses such as the herbicide glyphosate on nutrient assimilation and seed composition are also in progress. Experiments were initiated for all sub-objectives relating to optimization of the Early Soybean Production System (ESPS) and pest management strategies for the mid-southern United States.
Effect of Maturity and Heat on Seed Composition in the Early Soybean Production System. Maintaining a high level of protein and oil in soybean seed is a major goal of the soybean industry, but seed protein and oil content significantly change, depending on cultivar, maturity date of the cultivar and the environment under which they grow. To investigate the contribution of each of these variables to total protein and oil content separately, two sets of isolines each were grown which differ in maturity genes, but each set (Clark or Harosoy isolines) has the same genetic background. Protein percentage among Clark isolines increased as days to maturity increased, and oil percentage decreased as days to maturity increased among Harosoy and Clark isolines. Temperature had significant effect on seed composition; however, maturity explained a greater percentage of the variation in protein and oil. Soybean breeders can use this information to develop new soybean varieties with higher seed protein and oil, depending on their region.
Nitrogen Metabolism and Seed Composition as Influenced by Foliar Boron Application. Boron is an essential nutrient for crop growth and seed quality, and low boron in soil leads to yield loss and low seed quality. Although the Mississippi Delta soils contain enough boron to support soybean production, its absorption by soybean plants under high heat and drought may not be enough to support high yield and seed quality. Two boron sprays increased protein content, decreased oil content, increased oleic acid, and decreased linolenic acid in seed which could lead to improved stability and shelf-live. Soybean producers can spray boron under drought condition or boron deficient soils to gain the beneficial effect of increasing protein, increasing oleic acid and decreasing linolenic acid in soybean seed.
Influence of Charcoal Rot on Seed Composition and Nutrient Uptake in Soybean. Charcoal rot is a major disease in the southern soybean region. A field experiment was conducted at Stoneville, MS, to investigate the effect of disease and irrigation management on seed composition. Soybean cultivars with moderate resistance (DT 97-4290) to charcoal rot maintained normal levels of seed protein and oil when plants were grown in fields infested with the fungus compared to susceptible (Egyptian and Pharoah) cultivars. Since there are no commercial resistant cultivars available, tolerant cultivars with appropriate water management may provide soybean producers with an alternative approach for charcoal rot management.
Bellaloui, N., Smith, J.R., Ray, J.D., Gillen, A.M. 2009. Effect of Maturity on Seed Composition in the Early Soybean Production System as Measured on Near-isogenic Soybean Lines. Crop Science.49:608-620
Bruns, H.A. 2009. A Survey of Factors Involved in Crop Maturity. Agronomy Journal. 101:60-66
Bellaloui, N., Mengistu, A., Paris, R.L. 2008. Soybean Seed Composition in Cultivars Differing in Resistance to Charcoal Rot (Macrophomina phaseolina). Journal of Agricultural Science. vol. 146(6):667-675