Genetically Diverse Sources of SCN Resistance in Soybeans.

In the United States, Soybean Cyst Nematode (SCN, Heterodera glycines) is the most damaging pest on Soybean (Glycine max). In 2007, the yield losses caused by SCN in the USA included 94 million bushels. SCN causes yield reductions by feeding on plant nutrients, retarding root growth and, inhibiting Bradyrhizobium nodulation. Genetic resistance has been the most effective means of controlling SCN. However, nematode populations are genetically highly variable and have adapted to reproduce on resistant cultivars overtime because resistance primarily traces to two soybean accessions: PI88788 and PI548402 (Peking).  More than 100 sources of nematode resistance are available in soybean. Cluster analyses have identified genetically diverse soybean lines from both PIs 88788 and 548402. Some of these diverse lines include PIs 438489B, 437655, 507354, 467312, 22897 (Columbia), 89772 , 507471 and 567516C and potentially may have different  genes for SCN resistance. Genetically diverse sources may provide durable resistance to SCN.  But, these diverse sources are agronomically highly undesirable and very poor yielders. Crosses were made with high yielding soybean cultivars to generate progenies for selection. The high yielding lines include, ‘5601T', ‘Hutcheson', 'Bolivar' and LG01-5822. The progenies are individually advanced using a combination of single-plant-selection and/or modified bulk selection methods. Progenies with resistance are selected in F3-derived F5, F6 or F7 generations in greenhouse bioassays and confirmed with molecular markers (SSR) in agronomically desirable lines followed by field evaluations. These selections for SCN resistance are in various phases for their development with durable resistance and release.