CHROMOSOME DOUBLING OF BARLEY HAPLOIDS BY NITROUS OXIDE AND COLCHICINE TREATMENTS

Abstract

Hybridization of Hordeum vulgare L. (2n = 14) with H. bulbosum L. (2n = 14) results in a high frequency of haploids of H. vulgare through selective elimination of H. bulbosum chromosomes. Doubled haploids were produced by nitrous oxide (N₂O) or 0.1% colchicine with and without dimethyl sulfoxide (DMSO) treatments. Pollinated florets (vulgare × bulbosum) were treated with N₂O under 21.1 × 10⁻³to 42.2 × 10⁻³ kg/m²pressure (30 to 60 psi) and the frequency of doubled haploids ranged from 0 to 100%, depending upon pressure and duration of exposure. However, the frequency of seedlings from the most effective N₂O doubling treatment was very low (0.5%) whereas 17% of the florets pollinated in the controls resulted in seedlings. Of the haploid seedlings treated with either 0.1% colchicine or colchicine plus DMSO, doubled sectors occurred in 37.4 and 55.8% respectively. Seed was also obtained from 3% of the untreated plants indicating a low frequency of natural chromosome doubling. The proportion of doubled tillers per plant was 61.6% in colchicine plus DMSO treatments and 30.8% in the colchicine treatments. Colchicine plus DMSO was the most efficient treatment for doubling barley haploids during early stages of development.