Abstract: Plant regeneration from protoplasts isolated from haploid cell suspensions of commercial supersweet maize (SS 7700) was achieved and the plants were survival after transfer into soil in pots. Protoplast plating efficiency obtained from feeder layer system was 130 folds higher as compared with conventional liquid culture method, the composition of protoplast culture medium, the pore size of supportive membrane filter and the relationship between protoplasts and feeder cells were critical for callus formation. An enriched medium containing vitamins, organic acids, amino-acids and other organic substances such as coconut water could extremely improve callus formation. Filters with pore size within the range of 0.22–8.0 μm in diameter was useful. Filters with smaller pore size of 0.04 μm or larger 11 μm appeared to decrease the frequency of protocolony formation. The feeder cells which belong to the same species (Zea mays) as protoplasts greatly increased protoplast plating efficiencies as compared to those of feeder cells belonging to other species such as Avena nuda and Nicotiana tabacum. Among 11 protoplast-regenerated plants examined, 10 plants were haploid and one plant was diploid.

Key words: Zea mays L., Supersweet maize, Haploid, Feeder layer, Plant regeneration