Induced Deletion Mutagenesis Results in Soybean Seed Composition Variation.

Induced mutagenized populations have proven to be useful tools across a number of species for investigating gene function as well as creating new genetic and phenotypic variation for crop improvement. A soybean [Glycine max (L.) Merr.] deletion mutagenesis population has been created at the University of Minnesota by exposing soybean seeds from the Minnesota breeding line M92-220 to fast-neutron bombardment. To date, thousands of mutant lines have been evaluated for seed composition variation.  Multi-environment field trials revealed that seven lines possess significantly different protein and/or oil levels, higher or lower than the un-mutagenized parent.  Array-based comparative genome hybridization experiments were carried out for initial genetic characterization of these seven lines. Each of the lines was found to have one to four mutations that ranged in size from 1 kb to 1800 kb. The objective of the present study was to further characterize these mutant lines and confirm the apparent effect these chromosome deletions have on seed composition. To accomplish our objective, crosses were made between each of the seven mutant lines and the wild type parent as well as four unrelated soybean genotypes (Anoka, Evans, Minsoy, Noir1). Segregating F2 progeny from each cross were evaluated in St. Paul, MN during the 2011 growing season.  Seeds were space planted and a drip irrigation system was installed to minimize potential environmental variability. Leaf tissue for DNA analysis was collected from each F2 plant (10,000+). Plants were harvested individually, and seed protein and oil content were determined using near infrared spectroscopy. Based on phenotypic distributions of select BC1F2 populations and outcrossed F2 populations, 10-20 individuals from the distribution tails were selected for DNA characterization. Backcrossed lines were screened with mutation-specific markers and outcrossed lines were assayed with the Illumina Soy GoldenGate Assay (1536 SNPs).  Mutation/marker-trait association results will be presented.