Haploid Production through Anther Culture in Saintpaulia Species

African violet (Saintpaulia ionantha) cultivars are generally not fixed as homozygotes because the plant is easily propagated by leaf cutting. However, homozygotes are useful for breeding. Anther culture is a rapid method of obtaining homozygotes via doubling the anther-derived haploid chromosome set. In this study, the optimal anther culture conditions for highly-efficient haploid production were investigated using seven natural species and eight cultivars in the genus Saintpaulia. Anther culture of African violet was performed to determine the appropriate phytohormone concentrations for shoot formation. Microspores at uninucleate stage that were suitable for culture were observed in anthers of length 2.5–3.0 mm (natural species) or 3.0–5.0 mm (cultivars) at 8–9 days after bud formation began. Treatments contained 0.1, 1.0, or 10.0 mg/L of N⁶-benzyladenine and of naphthaleneacetic acid in a total of nine concentration combinations. The most effective combination for shoot formation was 1.0 mg/L of each phytohormone in the cultivar ‘Tomahawk’. In that treatment, shoot formation percentages from anthers ranged from 0% to 62.5% for natural species and 0% to 93.8% for cultivars. Three of seven natural species and five of seven cultivars showed statistically similar shoot formation percentages to ‘Tomahawk’. These results suggested that the applicability of these anther culture conditions was 43% in natural species and 71% in cultivars. Microscopic observations of chromosomes in root-tip cells of anther-derived plants showed an average haploid efficiency of 64.3%. Some haploids had different phenotypes from their parent plants in both leaf and flower color and shape. Recessive traits, such as single flowers, white flowers, and plain foliage, were observed in haploids. Colchicine treatment of ‘Tomahawk’ was performed to produce doubled-haploid plants. The most effective conditions for producing doubled haploids were 0.05% colchicine for 3 days. Most of the doubled haploids retained the characteristics of their parent haploid. Stomatal cell lengths in polyploids were ranked as tetraploid (doubled diploid) > diploid > doubled haploid > haploid. Although the doubled haploids should be confirmed the homozygous through progeny tests, they may be used practically as breeding stocks. This new method allowed the production of doubled haploids of African violet in as little as 392 days.