Submitted to: Molecular Genetics and Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2004
Publication Date: 5/15/2005
Citation: Atibalentja, N., Bekal, S., Domier, L.L., Niblack, T.L., Noel, G.R., Lambert, K.N. 2005. A genetic linkage map of the soybean cyst nematode, Heterodera glycines. Molecular Genetics and Genomics. 273(3):273-281. Interpretive Summary: The soybean cyst nematode (SCN) is the most destructive pathogen of soybean in the United States, causing annual crop loss in the hundreds of millions of dollars. In spite of the nematode's importance, little is known of its genetics. The importance of this linkage map is that it can provide for genomic localization of important genes such as those involved in parasitism. In this research we identified the location of the SCN parasitism gene HG-CM-1 (Heterodera glycines chorismate mutase 1) and a molecular marker that is associated with virulence (resistance breaking biotypes)on several sources of resistance in soybean to SCN. This genetic linkage map is the second one developed for a plant-parasitic nematode and the first published for SCN. This ground breaking work is the most important research done thus far to understand the genetics of SCN.
Technical Abstract: A genetic linkage map of the soybean cyst nematode (SCN), Heterodera glycines, was constructed using a population of F2 individuals from crosses between two highly inbred SCN lines, TN16 and TN20. Amplified Fragment Length Polymorphism (AFLP) fingerprinting was conducted on 63 F2 progenies using two restriction enzyme combinations, EcoRI/MseI and PstI/TaqI, and 38 primer combinations. The same F2 progenies were genotyped for Hg-cm-1 (Heterodera glycines chorismate mutase), a putative virulence gene, with real-time quantitative PCR. Some of the markers were distributed non-randomly. Even so, of the 230 (229 AFLP and the Hg-cm-1 locus) markers analyzed, 130 mapped onto nine major linkage groups (corresponding to the haploid number of chromosomes in H. glycines) and one minor group (length < 30 cM) at a minimum LOD of 3.0, for a total map distance of 540 cM. The Hg-cm-1 locus mapped to linkage group III along with 16 other markers. The size of the H. glycines genome was estimated at 659 cM from the linkage data, indicating that the current map represents 79 to 85% of the genome, with a map density of 5 cM, and a physical/genetic ratio between 90 and 96 kb/cM, based on a previous estimate of 61,000 kilobases for the physical genome of H. glycines.