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:
In our USB regional maturity group IV test, no line exceeded the yield of the best check but S07-5049 (69.4 bu/a) was 4 days earlier than the highest yielding check (AG 4703, 76.3 bu/a) and exceeded the yield of the next 3 highest yielding checks that were similar maturity as S07-5049. AG4103 was the second highest yielding check at 68.6 bu/a. In the our USB regional maturity group V test, S09-13635 yielded only 1.1 bu/a less than the best check AG 5606 and was within 0.2 bu/a of the top two public varieties (5601T and 5002T). S09-13635 has a pedigree that is 19% exotic germplasm from 4 exotic parents. In the Southern Preliminary IV-S Early Test, S09-10320 was just 0.3 bu/a lower yielding than the best check AG 4103 (52.3 bu/a). S09-10320 has a pedigree that is 38% exotic germplasm with 3 exotic parents in its pedigree. In the Southern Preliminary IV-S Late Test, S09-13608 yielded the same (52.8 bu/a) as the highest yielding check, AG 4903. S09-13608 has a pedigree of 38% exotic germplasm with 4 exotic parents, two of which are different from those in the pedigree of S09-10320. We have made 13 productive soybean lines with up to 50% exotic pedigree lines available for use by other soybean breeders for crossing in their breeding program. These 13 lines vary in maturity from late III to early V. There are 17 PIs involved in the pedigrees and have been yield tested from three to four years across four or more locations each year. Two lines are moderately resistant to SCN races 2, 3, 5, and 14 and root knot nematode; four lines are chloride excluders or tolerant to salt, and three lines are tolerant to sulfonylurea herbicides.