Fast-Neutron Mutagenesis Induced Variation for Protein and Oil Content In Soybean.

Induced mutagenesis can be a valuable tool for the purpose of: 1) creating novel variation for a particular trait of interest, and 2) studying the role of genes in functional genomics research.  Fast-neutron bombardment typically generates chromosomal deletions, effectively knocking out the function of the gene or genes within the deleted region.  The size and frequency of deletions within an individual depend, in part, on the radiation dose to which a seed is exposed.  A soybean [Glycine max (L.) Merr.] fast-neutron population development project was initiated in 2007 for the purpose of providing the soybean community with a valuable resource for genetic research.  The objective of the present research was to screen thousands of mutant lines from the population for the purpose of identifying individuals that differ in seed composition characteristics relative to the wild type (WT, M92-220; ~40% protein, ~20% oil).  Over 10,000 lines were evaluated for unique compositional variation via near infrared spectroscopy.  The initial screen identified 308 lines that exhibited a phenotype of interest.  Through further testing, 7 mutant lines were identified as having stable, robust compositional phenotypes over multiple environments.  The 7 mutant lines varied by 16.1 percentage points in protein concentration (-11% to +5.1%, relative to WT) and 5.6 percentage points in oil concentration (-3.6% to +2%).  To determine the sites of induced genomic modification contributing to the protein and oil phenotypes, microarray-based comparative genome hybridization experiments were carried out.  As expected, the majority of the mutations were deletions.  Size of deleted segments ranged from 1 -1800 kb with an average of 2.4 mutations per mutant line.  Backross and outcross populations have been developed and mapping experiments are underway to determine if significant QTL (from mapping) correspond to the genomic locations of the deletions.