Abstract

Stolon pieces of St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] were irradiated with gamma rays in an attempt to cause mutations.  A practical dosage for most genotypes was 4,500 rads.  This dosage caused considerable (50%) growth retardation and a mean survival of about 40% of single-node cuttings.   However, 'Bitterblue' and another accession were entirely killed at 4,000 rads.   At 4,500 rads, up to 7% recognizable mutants of accession FA-243 were obtained.   This proportion resulted when irradiated cuttings were propagated clonally and observed for 1.5 years in replicated microplots.  In addition to morphological variants, a chimeral anthocyanin change was noticed.  From this chimera arose a stable genotype with green stolons and white stigmas, whereas the source genotype (FA-243) had red stolons and purple stigmas.  Associated reduction in fertility from 56 to 0.6% suggested that the mutation arose as a small chromosome deletion.  Mutation breeding is effective in improving St. Augustinegrass when easily recognizable variants are needed.