Revitalizing Historic Soybean Mutant Resources Using New Genomic Tools

The recent genotyping of the USDA soybean germplasm collection has provide a wealth of data that is enabling new research goals and objectives.  Starting in the 1960’s, soybean researchers created a collection of near isogenic mutant lines, called the Soybean Isolines, by backcrossing one or more mutant alleles into the cultivars Clark, Harosoy, and Williams.  While many of the mutant alleles in the Soybean Isoline collection are agronomically detrimental, some of the alleles have positive effects on yield, insect resistance, and disease resistance.  The public release of the SoySNP50K genotyping data provided sufficient information to map the introgression intervals for many of the lines in the Soybean Isoline collection.  For the 23 mutant alleles we have currently mapped, the introgression intervals range in size from 32kb to 5,541kb, with a median side of 606kb.  The number of genes contained in these intervals range from 6 to 255, with a median gene number of 73.  Proof-of-concept of this mapping method was performed on the trichome mutant T31, resulting in the cloning and validation of the causative sequence polymorphism.  We are in the process of mapping and cloning additional genes using this method. This work provides a roadmap for furthering knowledge of soybean gene function and introgressing potentially valuable mutant alleles into elite germplasm.