Induction of a dominant semidwarf mutant in barley.

About 6, 600 air-dried barley seeds with genie male sterility were treated with 8mM sodium azide (NaN₃) for two hours. They were sown in the field and were open-pollinated to translocation homozygous lines derived from Mars. In the F₁generation, only seven plants, which showed green lemmas and six-rowed spikes, were found to be semidwarf compared with most of all of the F₁plants. Their rachis was not shortened and the seed size was not smaller than that of the plants with a normal height. The second internode was markedly shorter than the other internodes. In the F₂generation, progeny from six selfed semidwarfs produced 135 semidwarf plants and 36 non-semidwarf plants. This was a satisfactory fit to a 3: 1 ratio expected for a single locus with two alleles, the mutnat allele (D) giving the dominant dwarf phenotype. Furthermore, reciprocal crosses were made between one semidwarf F₁plant and the cultivar, Misato Golden. F₁progeny from one semidwarf plant segregated into 12 semidwarf plants and 8 non-semidwarf plants, which gave a good fit to a 1: 1 ratio. This semidwarf gene (D) showed an independent inheritance from genes controlling orange lemma and male sterility which was located on chromosome 6 and from a gene controlling rough/smooth awn located on chromosome 7. In the F₃generation, 10 ppm of gibberellin A₃ (GA₃) was applied to a semidwarf homozygous line for three weeks after the sowing date. After the application of GA₃, the length of the first leaf sheath was measured. The first leaf sheath of the male sterile line was elongated by 207% compared with that of the untreated plant. The percentage of elongation in the semidwarfs was not different from that of the male sterile line or was higher than that of Mars. It was, therefore, concluded that semidwarf gene, D, is sensitive to GA₃.<BR>Consequently, it was demonstrated that the new type of dominant semidwarf gene induced by sodium azide did not affect the spike length and that it was sensitive to GA₃.