Location: Crop Genetics Research2010 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 to introgress low linolenic acid, mid oleic acid and low phytic acid traits into soybean adapted to the Mid South region were successfully made. Crosses were made to improve yield and charcoal rot resistance potential were successful. In most cases, sufficient seed was obtained to proceed with experiments. Selections from F2:5 lines were made for high and low oleic acid and were screened for fatty acid. Work to use plant introductions to identify new sources of genes which increase oleic acid in soybean oil continues. Selections from several low linolenic acid populations were shown to have linolenic acid ranging from 1.74% to 2.55%. Simple probe markers for low linolenic acid used to screen BC1F1 (hybrids) plants identified plants double heterozygous for the markers, and populations from these plants will be grown in 2010 and screened for the markers. Seed from individual F2 plants were screened for reduced phytate by measuring free phosphorus in the seed and selections were made for trials in 2010. Simple probe markers for low phytate used to screen BC1F1 (hybrids) plants identified plants double heterozygous for the markers, and populations from these plants will be grown in 2010 and screened for the markers. Charcoal rot resistance screening of early generations in a non-irrigated inoculated nursery continues. Asian soybean rust screening in Paraguay found highly resistant lines which need to be retested. Hybridization of elite lines to rust resistance lines continues. The program to combine rust genes Rpp1b with either Rpp2 or Rpp4 resistance genes produced eight BC1F2 populations from one cross, and advanced four BC1F5 populations for testing in 2010. One line with resistance to soybean cyst nematode race 3 and southern root-knot nematode was placed in the Uniform Soybean Tests for a second year. Two additional lines were advanced from the preliminary test to the uniform tests. New computer programs that use more accurate statistical models were used for the first time to analyze data from the Uniform Soybean Tests – Southern States and to produce the final report. An experiment indicated that both planting date and irrigation/drought significantly altered seed protein, oil, and fatty acids. A greenhouse experiment showed that seed protein, oil, and fatty acid significantly varied depending on the seed’s location on the main stem of the plant. A study of genetically related lines that varied for maturity (isolines) showed that the contribution of temperature, maturity, and genetic background depends on the type of sugar or mineral being studied. Experiments using slow wilting germplasm to understand drought tolerance continue. A field experiment showed that fertilization with sulfur or sulfur and nitrogen combined had no yield benefit, but sulfur and nitrogen fertilizers affected seed composition. Experimental results showed that glyphosate did not inhibit boron accumulation as it does for other cation nutrients (positive charge), indicating that tank-mixing of glyphosate with a negative ion fertilizer is possible without negative effect.
1. Glyphosate does not Inhibit Boron Accumulation in Leaves or Seed when Tank-mixed with Nutrient Solutions. Previous results showed that plant uptake of nutrients with positive charges (cations) is inhibited when nutrient solutions are tank mixed with glyphosate. Application of boron or boron with glyphosate combined increased boron in the seed and leaves, and increased nitrogen metabolism rates by enhancing the activity of the enzymes nitrate reductase and nitrogenase. This research showed that application of glyphosate alone, boron alone, or glyphosate-boron combined increased protein, oleic acid, and total amino acids in seed, and decreased oil and linolenic acid. The results demonstrated that the mechanism of glyphosate-boron interaction and uptake may differ than those of cation (positively charged) nutrients. We conclude the inhibition effects of glyphosate on nutrients may depend on type of nutrient as defined by its ion (positive or negative charge). Boron can be mixed with glyphosate and foliar-applied in one operation, decreasing growers’ production cost.
2. Glyphosate Alters Nitrogen Metabolism, Seed Composition and Seed Mineral Content. Effects of glyphosate application to sensitive and resistant glyphosate soybean on seed mineral nutrition and seed composition (protein, oil, and fatty acids) have become a concern to growers and the scientific community. Scientists at USDA-ARS Stoneville conducted field and greenhouse experiments to investigate the effect of glyphosate on mineral nutrition, seed composition, and nitrogen metabolism. Results showed that glyphosate altered nitrogen metabolism, seed composition and seed mineral content. Since there are inverse relationships between seed composition constituents, the increase or decrease in a constituent would occur at the expenses of other. This research could help finding a better glyphosate management system to maintain high seed quality. Also, understanding the implication of glyphosate on seed composition and mineral nutrition would help soybean agronomists and breeders seeking to improve seed composition and mineral nutrition qualities.
3. Improved Quality of Statistical Analysis of the Uniform Soybean Tests - Southern States. The Uniform Soybean Tests are used by public and government soybean breeders to test elite breeding lines that ultimately lead to the release of varieties. This program allows breeders to test lines in a wide range of conditions which they might not otherwise be able to do. The statistical analysis programs were updated to use a mixed model analysis of variance which is a more accurate statistical modeling method than what was previously used. This allowed breeders to have the most accurate statistics to make better decisions on variety releases. In addition, the data processing was updated to be more automated and the results more compatible with commonly used computer programs, which increased the efficiency of the process.Bruns, H.A., Abbas, H.K. 2009. Clipping corn plants at the 3 and 5 leaf growth stage fails to simulate uneven emergence. Crop Management. doi:10.1094/CM-2009-1016-01-RS.