Gibberellin-responding and non-responding dwarf mutants in foxtail millet

The sensitivity of foxtail millet (Setaria italica Beauv.) dwarf mutants to GA was studied. Seedlings of dwarf mutants, Aininghuang (ANH) and CH84113 were treated with GAs (GA(1), GA(4), GA(9), GA(19) and GA(20)) using the micro-drop method, or by soaking in GA(3) solution. Plants were also sprayed with GA(3) solution at the jointing stage. It was found that ANH was a GA-responding dwarf mutant, whose leaf blade, leaf sheath and internode length increased significantly after GA application, whereas CH84113 was a non-GA-responding dwarf mutant. However, the mesocotyl in etiolated seedlings of both ANH and CH84113 responded to exogenous GA(3) in a similar way. With the help of an enzyme-linked immunosorbent assay, it was found that the endogenous GA(1+3) level in leaves was lower in the GA-responding dwarf mutant ANH, but higher in the non-GA-responding dwarf mutant CH84113, compared with levels in normal cultivars.