Regeneration of haploid plants from isolated microspores of asparagus (Asparagus officinalis L.).

High percentages of micro-calli and micro-derived embryos were produced from isolated asparagus microspores at late uninucleate stage on MS liquid medium supplemented with 1.0 mg l(-1) 2,4-D and 0.5 mg l(-1) BA. Two types of calli, namely compact callus (CC) and loose callus (LC), were found. Plantlets were regenerated via organogenesis, when these calli were transferred onto MS solid medium supplemented with 1.0 mg l(-1) BA and 0.2 mg l(-1) IBA 6 weeks. Embryos were produced from liquid cultured microspores, or from solid cultured micro-calli. The frequencies of haploid plant production from organogenesis and embryogenesis were compared. Effects of plant growth regulators on callus production, plantlet regeneration, and haploid plant production were tested. The combination of BA 1.0 mg l(-1) and IBA 0.2 mg l(-1) resulted the highest precentage of haploid plant production (7.7% from CC, 4.3% from LC).