The effects of genotypes and media composition on callogenesis, regeneration and cell suspension culture of chamomile (Matricaria chamomilla L.)

Background: Chamomile is an important herb being used widely for medicinal purposes. Its multitherapeutic, cosmetic, and nutritional values have been established through years of traditional and scientific use and research. Increased use of medicinal plants necessitates rational use as well as sustainable production of such genetic resources. Plant in vitro micro-propagation poses unique opportunities for sustainable production of medicinal herbs, their regrowth and conservation. The present study aimed to investigate the effects of different explants, plant growth regulators (PGRs) combinations and media type on callogenesis, in vitro regeneration and cell suspension of six chamomile genotypes to enhance its sustainable production.

Methods: The shoot, lateral sprout, and leaf derived explants of six chamomile genotypes including Isfahan, Shiraz, Kazeron, Goral, Sharokashari and Presso were used for direct and indirect regeneration. For indirect regeneration various doses of NAA and kinetin were used to induce calli which were cultured on MS media containing PGRs for direct and indirect regeneration. Later, cell suspension was established and morphological characterization of CrO₃ stained cells was carried out using microscopy.

Results and discussion: Our findings revealed that the highest callus percentage and callus volume were observed from lateral sprouts and shoots of genotype Isfahan on MS medium containing 1 mg/L NAA and 1 mg/L kinetin. The in vitro regeneration was found to be genotype dependent while 77% and 77.5% was the highest percentage for indirect and direct regeneration, respectively. Additionally, the maximum shoot number (two shoots/explant) and shoot length (2.22 cm) were also observed in Isfahan genotype. Cell suspension culture showed the highest fresh weight (18.59 g) and dry weight (1.707 g) with 0.75 g inoculum of the callus derived from lateral sprouts cultured on MS medium. Microscopy of CrO₃ stained cells was carried on each 3rd day for 27 days that revealed larger and spongier cells in the early days as compared to final days when the cell number was greater but cell size was smaller.

Conclusion: The callogenesis, organogenesis, and cell suspension culture of chamomile may be genotype dependent. Hence, optimization of media ingredients and culture conditions is of utmost importance for devising tissue culture based conservation strategy of any chamomile genotype and secondary metabolite production.