Effect of genotype on callus induction, shoot regeneration, and phenotypic stability of regenerated plants in the greenhouse of <i>Primula ssp.</i>
Genotypic differences between six genotypes of Primula vulgaris could be observed in callus induction rate, type of callus, root formation during the callus phase, and shoot regeneration rate. The shoot regeneration rate ranged from zero to 11.6 shoots per explant. There was no correlation between callus induction rate and shoot regeneration rate. Callus consistency and colour were an indicator of the organogenetic capacity of callus. An experiment with different periods of treatment with 4.0 mg l 2,4-dichlorophenoxyacetic acid and 2.0 mg l21 thidiazuron revealed that the shoot regeneration rate varied tremendously between genotypes. In two genotypes a period of 8 weeks on medium with plant growth regulators was sufficient to induce shoot regeneration. In three other genotypes a longer induction period was not able to overcome low regeneration capacity. However an increase in shoot regeneration rate was observed after 16iV32 weeks of induction. Phenotypic stability was also strongly dependent on genotype. In three genotypes the majority of regenerated plants looked normal and were diploid. Aberrations like abnormal growth habit, crinkly leaves, deviation of flower colour or lack of pollen formation occurred in only one genotype at a very low frequency (1.5 genotypes between 12.5 and 18.1 regenerants was tetraploid.