@article{gizlice_carter_gerig_burton_1996, title={Genetic diversity patterns in North American public soybean cultivars based on coefficient of parentage}, volume={36}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci1996.0011183X003600030038x}, abstractNote={The genetic relatedness of North American soybean [Glycine max (L.) (Merr.)] may threaten long‐term breeding progress. To alleviate this problem, we propose that breeders diversify applied programs by capitalizing upon genetic patterns that may exist in cultivated germplasm. To date, only one diversity pattern, the well‐known North‐South distinction, is explained in applied breeding. Our objective was to identify and quantify additional factors influencing diversity in 258 cultivars released by public agencies during 1945 to 1988. We theorized that maturity group effects (MG, as a hybridization restriction factor), location of breeding programs (BP, as a selection factor), and breeder intuition and success factors beyond MG and BP may all influence the soybean cultivar diversity patterns. The patterns of diversity associated with the first two factors, MG and BP, were examined by quantifying average coefficient of parentage (r) within and between MG and BP. Multidimensional scaling (MDS) was applied to the r matrix to produce coordinates for pictorial depiction of MG and BP. To examine the third factor, breeder intuition and success, the MDS coordinates were also subjected to a nonhierarchical cluster analysis that revealed nine major clusters of soybean cultivars. A regression analysis was employed to determine the relative importance of North‐South, MG, BP, and cluster patterns in explaining variation in the r matrix. The South‐North distinction accounted for only 21% of variability in cultivar relations indicating the presence of other major patterns of diversity. The MG, BP, and clusters independently explained 32, 42, and 57% of the total variation in the cultivar pedigrees. Clusters most efficiently revealed patterns of diversity, and we propose the use of these clusters in the further study and management of soybean diversity. Multidimensional scaling coupled with nonhierarchical cluster analysis was a highly promising approach to the study of diversity.}, number={3}, journal={CROP SCIENCE}, author={Gizlice, Z and Carter, TE and Gerig, TM and Burton, JW}, year={1996}, pages={753–765} }
 @article{gizlice_carter_burton_1994, title={Genetic base for North American public soybean cultivars released between 1947 and 1988}, volume={34}, DOI={10.2135/cropsci1994.0011183X003400050001x}, abstractNote={A negative consequence of four decades of modern soybean breeding is the evolution of cultivars with complex pedigrees that tend to obscure the genetic base of applied breeding. A result is that the genetic base of North American soybean [Glycine max (L.) Merr.] has never been described fully. We attempt here to define the genetic base as sets of genotypes that contain 99% of the genes found in modern cultivars. For clarity, the base is defined both in terms of the original plant introductions (ancestors) used for hybridization and in terms of the progeny derived from them. In a first analysis of pedigree data, 80 ancestors were identified and their fractional genetic contributions to 258 cultivars were computed using coefficient of parentage (r) estimates. In a second analysis, six breeding lines and 133 cultivars were identified as first progeny of the 80 ancestors, and their contributions as parents to modern cultivars were computed using r. This analysis revealed that 91 first progeny constituted 99% of the genes found in modern cultivars. Lincoln and Harosoy in the North and Lee and its full sib (D49‐2491) in the South contributed nearly 40% of the genes to North American cultivars. Nearly 75% of the genes in modern cultivars trace to 17 first progeny released before 1960, indicating that breeders have remained dependent upon this early genetic core of breeding material. For practical study of the genetic base of North American soybean, we propose using a combination of the results from the two analyses described here. Twenty‐eight ancestors and seven first progeny were identified which contribute 95% of the genes found in modern soybean cultivars. This group of 35 genotypes would be a useful core collection for evaluating the presence, absence, or distribution of a trait in North American soybean cultivars.}, number={5}, journal={Crop Science}, author={Gizlice, Z. and Carter, T. E. and Burton, J. W.}, year={1994}, pages={1143} }
 @article{gizlice_carter_burton_1989, title={THE IMPACT OF MATURITY AND GENOTYPE ON BLEND PERFORMANCE IN GROUP-V AND GROUP-VII SOYBEAN CULTIVARS}, volume={81}, ISSN={["0002-1962"]}, DOI={10.2134/agronj1989.00021962008100040003x}, abstractNote={Abstract}, number={4}, journal={AGRONOMY JOURNAL}, author={GIZLICE, Z and CARTER, TE and BURTON, JW}, year={1989}, pages={559–562} }