Morphological mutants of St. Augustinegrass induced by gamma ray irradiation

St. Augustinegrass is a widely used turf and pasture grass in the southern US. Raleigh is a cultivar known for superior cold tolerance than other St. Augustinegrass cultivars. However, its coarse-leaf texture and long internodes are undesirable when planted in home lawns. Mutagenesis by gamma ray irradiation was employed to treat node cuttings and calli for inducing semi-dwarf growth phenotype. Dosages of 48.5 and 72.6 Gy were determined as LD50 and LD20 for the cuttings, respectively. Regeneration ability of callus was greatly reduced when irradiated with higher dosages (over 100 Gy). Thirteen morphological mutants were identified among over 3000 node cuttings and 80 pieces of calli treated. Most mutants were semi-dwarf type with reduced internode length and leaf blade length. One mutant had much less and shorter stolons and displayed an upright and tufty growth pattern. The altered morphological traits were stable as shown by their growth performance in various locations and conditions.