1a. Objectives (from AD-416):
Our objective is to identify and utilize exotic germplasm to improve U.S. soybean productivity. We will deliver 1) high yielding lines derived from exotic germplasm that are available to all U.S. soybean breeders developing new cultivars, 2) quantitative trait loci (QTL) affecting yield with the positive allele derived from exotic germplasm and the DNA markers associated with these loci, and 3) lines derived from exotic germplasm that will improve the yield and seed quality in the Early Planting Production System of the mid-south.
1b. Approach (from AD-416):
High-yielding experimental lines will be developed from exotic germplasm to expand the genetic base and accelerate the rate of yield improvement of soybean production in the U.S. This breeding project will use over 150 soybean introductions and many experimental lines derived from these introductions in past USB projects. These introductions include modern Asian varieties that are unrelated to U.S. cultivars, diverse primitive varieties that predate scientific plant breeding, and wild soybean. The number of exotic lines that we are using exceeds the total number of all the ancestral lines, regardless of the size of their contribution, of all of the current varieties grown in the U.S. Our projects are located in all major soybean-growing regions of the U.S. so that new genes for increasing yield from exotic germplasm will be accessible to soybean breeders and eventually soybean farmers in every soybean-producing state. We will also be testing exotic germplasm and lines derived from exotic germplasm in the Early Planting Production System of the mid-south to select for high yield and improved germination rates in the harvested seeds. Concurrently with developing high yielding experimental lines, we are developing sets of lines (mapping populations) that will allow us to begin the process of identifying specific genes (quantitative trait loci, QTL) from exotic germplasm that can increase yield of commercial varieties and then to confirm those QTL in independent populations.
3. Progress Report:
We made 256 experimental lines derived from exotic germplasm available to commercial soybean breeding companies for yield testing and use as parents. The check varieties used in these tests are the same as in the USDA Uniform Tests. In a maturity group III cooperative yield test with private industry that was grown at 17 locations, five lines with the same pedigree yielded more than the best check. These lines had 8 exotic accessions that contributed 52% of the pedigree. The best line was 3 bu/a better than the best check. In a maturity group IV cooperative yield test with private industry that was grown at 13 locations, 10 lines exceeded the yield of the best check with the highest yielding experimental line, LG10-7880, exceeding the yield of the best check by 4.4 bu/a. By pedigree, 31% of the parentage of this line came from 6 exotic accessions. In an advanced cooperative maturity group III yield test with private industry that was grown at 20 locations, LG10-2688 was 1.4 bu/a higher yielding than IA 3023 in 2012 and averaged over 28 locations in two years it was 1.5 bu/a higher yielding than IA3023. This line had 31% of its pedigree derived from 5 exotic accessions. The high yielding lines reported in these tests that there were not significantly different from the best check were derived from 50 exotic soybean accessions not previously used in U.S. soybean breeding. Since more than 95% of the currently used gene pool of commercial soybean breeding is derived from only 35 ancestral lines, the diversity in our project has the potential to more than double the diversity available to U.S. soybean breeders and that diversity is available in high yielding experimental lines.