Effect of explant type and different concentrations of growth regulators on micropropagation of Pelargonium hortorum Maverick at In vitro condition

Geranium is one of the most economically important pot plants in the world and is widely used in landscape. In order to produce disease-free and homogenic plants, proliferation by tissue culture is one of the alternative methods for mass production of this valuable plant. The aim of this study was to achieve an efficient and rapid method for micropropagation of Geranium by comparing leaf discs, petiole, stem and root explants on MS and B5 media.

For callus induction, stem, leaf and root explants were cultured on MS basal medium with 11 different kinds of hormonal combination, containing auxin (NAA and IAA) and cytokinin (BAP, Kin and Zeatin) with various concentrations. For direct regeneration of stem, leaf and petiole explants, 10 different culture media were used in MS and B5. After shooting, the explants were transferred to B5 culture medium containing auxin (0.5 mg/l NAA and 0.5 mg/l IAA) for root induction.

The best hormonal treatment for callus induction was 1mg/l NAA+10mg/l Kin by using stem and leaf explants as 92.5% and 88.75%, respectively. Also, the maximum fresh and dry weight of callus were related to stem explants on MS culture medium included 1mg/l NAA+10mg/l Kin, which were not significantly different from leaf explants on the same culture medium. The maximum percentage of direct regeneration and number of branches, respectively as 71.25% and 7.12 shoots, were related to stem explant on B5 medium containing 2mg/l BAP+1mg/l Zeatin, and the maximum shoot length, as 2.56 cm, was observed during direct regeneration in MS culture medium included 0.2 mg/l NAA+0.5 mg/l BAP+1 mg/l Zeatin. The shoots were successfully rooted and adapted to the environment.

The results of the present study were showed that the micropropagation of ornamental geranium plant is affected by the type of explant, the concentration of growth regulators and the type of culture medium and the stem explant is efficient in callus induction and direct regeneration.