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 a recurrent selection experiment, the seven original founder exotic parental lines of Cycle 0 (C 0) and the 10 selected parents of Cycles 1, 2, and 3 (C1, C2 and C3) were evaluated in eight locations during 2011-12 to evaluate progress in selection for yield and determine if selection for increased yield resulted in any correlated changes in other traits. After three cycles of recurrent selection, grain yield increased significantly (p<0.05) from a mean of 45.7 bu/a for C0 to a mean of 75.1 bu/a for C3. The response to selection had an average gain of 10.1 bu/a per cycle. The top 9 experimental lines were not significantly different from the three check cultivars. The increase in seed yield did not change the time to maturity. The significant progress for increased grain yield reported in this study using exotic germplasm material with many undesirable agronomic traits is a remarkable feat.