Role of growth regulators in the somatic organogenesis of haworthia inflorescences in vitro

This study investigated the effect of growth regulators on the somatic organogenesis of Haworthia inflorescences. The inflorescences of five Haworthia cultivars and one species were cultured on 1X and 0.5X MS media with/without growth regulators for organogenesis. Shoot and callus induction was observed for three of the five cultivars, whereas only callus induction was observed for the other two cultivars and one species. Of the two growth regulator-free media used, all explants performed better on ½ fold MS medium than on 1 fold MS medium in terms of shoot and callus induction. Conversely, among the six media supplemented with kinetin and 6-benzylaminopurine (BA), there was no shoot formation; however, a different response in callus formation was observed for H. splendens and ‘White Wolf’. The callus induction of H. splendens was more vigorous than that of ‘White Wolf’. In this study, better organogenesis from young upper parts of the inflorescences was observed. The highest shoot and root multiplication was observed on NAA containing medium, and no root formation was observed on BA containing medium. The highest shoot multiplication (20.8 ± 0.29) was observed for ‘Tiffany × Fertenon B Com’ on 1.4 mg·L^-1 BA containing medium within 18 weeks, whereas, the highest root induction was observed for Haworthia ‘Natalie’ on medium containing 0.05 mg·L^-1 NAA. The results revealed that different parts of Haworthia inflorescences showed different organogenesis responses. Therefore, this study contributes to a better understanding of the organogenesis response of Haworthia cultivars on different media.