Optimization of callusogenesis and rooting of two valerian (Valeriana officinalis L.) ecotypes using different concentrations of BAP and IBA

Introduction: Valerian (Valeriana officinalis L.) holds significant importance due to its medicinal properties, especially in traditional medicine. The increasing demand for it necessitates efficient propagation methods. Plant tissue culture, using growth regulators like BAP and IBA, can be an effective solution. This research, by examining the effects of different concentrations of these hormones on two ecotypes of valerian, aims to find optimal conditions for mass production of callus and roots, and ultimately, for the medicinal compounds of this plant.
Materials and Methods: In this study, the effect of different concentrations of BAP (1 and 2 mg/L) in combination with IBA (0, 0.5, and 1 mg/L) on callus formation and root production using leaf and petiole explants of in vitro seedlings from two ecotypes (Shiraz and Mashhad) was investigated in a factorial experiment under a completely randomized design with three replications. Seeds of the two valerian ecotypes, Shiraz and Mashhad, were used to produce in vitro seedlings and to evaluate callus and root production under tissue culture conditions. Various traits, including callus formation percentage, rooting percentage, callus diameter, number of roots, percentage of roots larger than 2 cm, callus and root fresh weight, and total fresh weight (including root and callus weight) were measured to assess root and callus production in leaf and petiole explants from the two valerian ecotypes of Shiraz and Mashhad. Finally, statistical analysis was performed, and after the treatments became significant, mean comparison of the data was done using Duncan’s test at a 5% probability level. MSTAT-C and SPSS Ver. 18 software were used for statistical analysis, and Excel software was used for drawing graphs.
Results: The results showed that for callus and root induction, the presence of exogenous auxin is essential, as callus and root formation were only observed in culture media containing IBA. With an increase in BAP concentration to 2 mg/L, the callus formation percentage increased by 54.16% in the Mashhad ecotype. In leaf explants, adding IBA to the culture medium led to an increase in callus formation percentage to 87.60%. The effect of different IBA concentrations on rooting percentage was significant, with the maximum rooting percentage achieved at concentrations of 0.5 mg/L (77.77%) and 1 mg/L (80.35%) of IBA. In the Shiraz ecotype compared to Mashhad, and in leaf explants compared to petioles, a greater number of roots were produced. The maximum number of roots (8.21), irrespective of IBA concentration, was obtained in culture media containing 2 mg/L BAP. Callus formation percentage was maximal in the Shiraz ecotype across all treatment combinations and in the Mashhad ecotype, except for leaf explants cultured in a medium containing 1 mg/L BAP combined with 0.5 mg/L IBA.
Conclusion: The results showed that the percentage of callus formation and rooting in the two ecotypes of Shiraz and Mashhad were different and depended on the type of hormonal combination applied. In general, the Shiraz ecotype performed better than Mashhad. In addition, petiole explants performed better in increasing the percentage of callus formation and callus diameter. Given that the leaf explant produced a higher percentage of roots with the desired length, this type of explant is recommended. The results showed that the amounts of endogenous hormones were different between ecotypes and explants, and the hormonal requirements at different stages of callus and root maintenance differed from the stages of callus and root induction from explants.