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 tests at 2 locations with 3 replications/test (Plaines GA and Mt. Olive, NC) G08-5385 RR and G08-5340 RR (selections from P97M50 x LG00-3372; where LG00-3372 is from the cross of PI561319A and PI574477) out yielded checks by 5 bu/a (AGS 758 RR) and 9 bu/a (AGS 606 RR). In tests grown at 3 locations (3 replications/location) G08-5536 RR yielded 96% of the check varieties (AGS 758 RR and G03-1187 RR). G08-5536 RR is also from the cross of P97M50 x LG00-3372. Of the 97 breeding lines in the 2011 Southern USB-Diversity Tests 4E, 4L, 5, 6, and 7/8 screened for southern root-knot nematode in the greenhouse, three diverse breeding lines in USBDIV-4E (S07-3666, V07-1216, V07-1205) and four diverse breeding lines in USBDIV-5 (R09-1148, S06-12316, NMS4-37-308-1, NLM09-77) were resistant and did not have an elite parent with known genes for southern root-knot nematode resistance. These breeding lines and their parents will be retested for resistance to confirm if their exotic parents are the possible source of their southern root-knot nematode resistance. The MG V accession PI 471931 was originally collected in Nepal. In the 1998 and 1999 Soybean Asian Germplasm Evaluation (SAGE) Test, PI 471931 yielded 94% of Manokin the MG V U.S. check variety. Based on its origin and competitive seed yield, it was selected as a potential donor of superior yield alleles. Three replicated tests of the 150 recombinant inbred lines (RILs) from a 5601T x PI 471931 population were grown at Plains, GA. The RIL population mean was 44.4 bu/a.The 150 RILs ranged from 25.7 bu/a to 57.9 bu/a while 5601T yielded 52.5 bu/a and PI 471931 yielded 41.7 bu/a. These data indicate that both parents are likely contributing unique alleles for high and low yield and there is a significant probability of identifying at least one yield QTL where the allele for increased yield is inherited from PI 471931. The 150 RILs will be planted in the Athens greenhouse and DNA will be isolated from leaf tissue of each RIL. The DNA will be sent to Beltsville, MD for SNP genotyping. In the 5601T x PI 157440 RIL mapping population, 150 RILs were planted at 7 locations from 2009 to 2011. Across locations, the highest yielding RIL (50.4 bu/a) exceeded the adapted parent 5601T (49.3 bu/a) while the lowest yielding RIL had lower seed yield (32.3 bu/a) than the low-yielding exotic parent PI 157440 (34.3 bu/a). Yield and agronomic data were collected and analyzed across locations. The SNP data on these RILs were associated with the yield data. A total of 14 QTL controlling the variation in yield were discovered, where 3 QTL on chromosomes 10, 13, and 20 inherited their positive alleles for greater yield from PI 157440.