Ethidium-Bromide Induced Mutations From Inflorescence Cultures of Indiangrass

Immature inflorescences of a Sorghastrum nutans (L.) Nash selection were cultured on CCm medium with 5 mg•L^-1 2,4-D and 1 mg•L^-1 BA for 5 weeks.  Callused inflorescence cultures were placed on CCm medium with 1 mg•L^-1 BA (CCmB¹) and 0 or 250 mg•L^-1 ethidium bromide (EtBr) for 1 day.  Cultures were transferred to CCmB¹ without EtBr for shoot regeneration, then to CCm without plant growth regulators for rooting.  Rooted shoots were transferred to soil under greenhouse conditions, then to the field.  Fifteen putative M₁ mutants with atypical phenotypes were detected among 71 regenerants, all from the EtBr treatment.  Two self-incompatible putative M₁ mutants were progeny-tested by using a wild-type Indiangrass seedling as the pollen parent.  M₁ selection ISU06-35 was a dwarf mutant whose M₂ testcross progeny segregated 1:1 tall:dwarf seedlings.  M₁ selection ISU06-56 was a red-flowered mutant whose M₂ testcross progeny segregated 1:1 green-flowered:red-flowered seedlings.  These results are consistent with both M₁ mutants being dominant nuclear mutations.