Screening for barley mutants with altered hormone sensitivity in their aleurone layers

A method, based on the diffusion assay of alpha-amylase on agar plates, was developed to screen for barley (Himalaya) mutants with altered sensitivity to gibberellic acid (GA(3)) or abscisic acid (ABA) in their aleurone layers. The seeds produced by sodium azide-mutagenized barley were screened for their ability to synthesize and secrete alpha-amylase when treated with different combinations of hormones. Various GA(3)-insensitive or supersensitive, ABA-insensitive, temperature-dependent GA(3)-insensitive, and constitutive mutants have been identified. Several stable mutants with altered GA(3) sensitivity were recovered. Two of the homozygous GA(3)-insensitive mutants have been preliminarily characterized. The GA(3)-enhanced production of alpha-amylase and release of phosphatase are hampered in these mutants. However, they have normal stem height, and the uptake of GA(3) by their aleurone layers appears to be the same as that of wild-type barley. They are most likely regulatory mutants affecting both alpha-amylase synthesis and phosphatase release.