Submitted to: Journal of Heredity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 8, 2005
Publication Date: June 9, 2005
Citation: Bilyeu, K.D., Beuselinck, P.R. 2005. Genetic divergence between north american ancestral soybean lines and introductions with resistance to soybean cyst nematode revealed by chloroplast haplotypes. Journal of Heredity. 96(5):593-599. Interpretive Summary: The genetic base of North American soybean cultivars can be broadened by using soybean germplasm with origins different than the ancestors of our North American soybean. The objective of this study was to evaluate soybean genetic diversity based on the genetic coding found in the chloroplasts of the North American ancestors and diverse plant introductions. We chose to examine the DNA coding of chloroplasts because they are inherited from mother plants to progeny and the slow rate of changes that occur in their DNA. Thus, lines with the same chloroplast DNA can be broadly grouped as being more related than lines with different chloroplast DNA. Our results confirmed that all North American soybean ancestors shared a single chloroplast type, meaning that they were closely related. Potentially divergent plant introductions also had the same chloroplast type as the North American ancestral soybean lines. However, many plant introductions with resistance to nematodes were found to contain a different chloroplast type. Using plant introductions with different chloroplast types might help plant breeders of North America to increase the genetic diversity of their soybean cultivars. An important first step in determining the choice of a plant introduction or germplasm for breeding would be to screen for chloroplast type. This information will be important to plant breeders in their attempts to increase the level of germplasm diversity in their soybean breeding lines and cultivars.
Technical Abstract: Identification and evaluation of germplasm resources can have a positive impact on modern crop breeding programs. Domesticated soybean [Glycine max (L.) Merr.] is a major crop with an established ancestral relationship to wild soybean (Glycine soja Sieb. & Zucc.) native to Asia. Genetic diversity can be assessed at different levels by identification of polymorphic alleles at different genetic loci, in either the plastid or nuclear genomes. The objective of this study was to evaluate soybean genetic diversity based on chloroplast haplotypes for North American ancestral lines, divergent G. max plant introductions, including lines resistant to soybean cyst nematode (SCN, Heterodera glycines Ichinohe), lines utilized for molecular genetics, and several G. soja plant introductions. Because of the requisite maternal inheritance and slow rate of mutation of the chloroplast genome, shared chloroplast haplotypes represent broad groups of genetic relatedness. At this broad level, our results confirmed the close relationship of North American ancestral soybean lines with the finding that all lines belonged to a single chloroplast haplotype group. A survey of G. max plant introductions representing potential sources of soybean genetic variation also demonstrated membership in the same chloroplast haplotype group as the North American ancestral soybean lines. More genetic diversity was identified in soybean lines utilized for single-nucleotide polymorphism (SNP) discovery and in a screen of lines with resistance to SCN.