Application of anther culture for efficient haploid production in the genus Saintpaulia

To optimize the production of anther-derived haploid plants of the genus Saintpaulia, the effect of plant growth regulator (PGR) concentration in the induction medium was investigated for six Saintpaulia species and eight cultivars of S. ionantha. The most effective PGR concentration for shoot formation was 1.0 mg l−1 for both N6-benzyladenine and α-naphthaleneacetic acid among the nine combinations of three concentrations (0.1, 1.0 and 10.0 mg l−1) of each PGR. Microspores at the uninucleate stage, which is the most suitable stage for anther culture, were observed in buds 2–3 mm (in Saintpaulia species) or 3–5 mm (in S. ionantha cultivars) in length. The frequency of shoot formation from anther-derived calli ranged from 0 to 63 % for Saintpaulia species and 0 to 100 % for S. ionantha cultivars. Five Saintpaulia species and seven S. ionantha cultivars formed shoots under the same PGR concentrations. These results demonstrated the versatility of the optimized conditions for anther cultures of diverse genotypes in Saintpaulia. Microscopic observation of the chromosomes of root-tip cells of anther-derived plants showed that the haploid efficiency was 40.0–85.7 % (average 66.6 %). Some haploid individuals showed phenotypic differences from the diploid parents in flower color and shape. Significant differences in stomatal guard cell lengths were observed between the diploid parent and some of the anther-derived haploids. The described protocol enabled haploids of Saintpaulia species to be obtained in a minimum of 286 days.