Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 4, 1997
Publication Date: N/A
Interpretive Summary: Only 17 ancestral lines contribute nearly 85% of the genes in all of the modern soybean varieties grown in the United States. This narrow genetic base is very likely to reduce the rate of yield improvement in future varieties as the level of genetic diversity in the commercially used gene pool decreases. The objectives of this research were to test the agronomic performance of experimental lines derived from exotic germplasm and to determine how much of the genetic diversity of their exotic parents these lines retain after selection for high yield. We identified experimental lines developed from crosses between modern varieties and exotic germplasm that yielded more than the modern variety. The best experimental lines were equal in yield to the best commercial varieties in the test even though one parent of these lines was exotic germplasm. Comparing the modern varieties and the experimental lines at the DNA level revealed that the experimental lines were genetically distinct from the modern varieties. In some cases the genetic contribution from the exotic parent was consistently associated with high yield. This is the first research that has conclusively demonstrated that low yielding, exotic germplasm can contribute to the improvement of yield of modern soybean varieties. We have also identified specific segments of soybean chromosomes that may affect yield although further research will be needed to confirm these results. The experimental lines developed in the research can be used in variety development programs to expand the genetic diversity of U.S. soybean breeding and to increase yield of future varieties.
Technical Abstract: Introgression of diverse germplasm into the current soybean [Glycine max (L.) Merr.] genetic base may increase genetic variability and lead to greater gains from selection. The focus of this research was to evaluate the genetic diversity and agronomic performance of experimental lines derived from plant introductions (PIs) maintained in the USDA Soybean Germplasm Collection, which are known to be genetically distinct from the ancestors of the modern North American soybean cultivars. Experimental lines containing 25 to 100% PI germplasm, their parents, and recently released public cultivars were evaluated for yield in seven environments in 1994 and 1995. Data from random amplified polymorphic DNA (RAPD) analysis were collected and genetic relationships among all genotypes were estimated. Hierarchical and non-hierarchical cluster analyses were used to display the relationships among these lines. Experimental lines were identified that yielded significantly greater than their adapted parent. The experimental lines always clustered with their adapted parent and never with the ancestors or non-parental cultivars. Comparisons of pairwise distances revealed that many of the high-yielding experimental lines were more diverse from the non-parental cultivars than their adapted parents. Specific RAPD markers were identified that were present in the high-yielding progeny and their exotic parent, but not in the adapted parent. The increased yields and specific markers provide evidence that exotic germplasm can contribute genes for high yield.