Effect of gibberellic acid treatment, and nutrient supply through detached tillers, upon haploid frequency in barley.

Haploids from Hordeum vulgare (2n = 14) X H. Bulbosum (2n = 14) crosses result after fertilization from the subsequent elimination of bulbosum chromosomes during early embryo development. Seed set from the cross is high but embryo culture is necessary to obtain seedlings. Application of gibberellin A3 (GA3) to pollinated florets was effective for increasing the frequency of haploid seedlings produced on both nutrient-fed detached tillers and intact plants. GA3 increased both seed set and embryo yield. The number of cells per embryo during its transition to the haploid state was increased two to three times following GA3 treatments. Enhanced embryo and endosperm development was attributed to increased mitotic activity. The number of visibly differentiated embryos was doubled to about 35 % of the cultured embryos after GA3 was applied to detached tillers in nutrient solution. About 70 % of the resulting haploid plants developed from the visibly differentiated embryos. The detached tiller technique offers a convenient method of culturing haploids from field-grown plants.