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Micropropagation of Micromeria croatica (Pers.) Schott

Micromeria croatica is an endemic species of the Dinaric Alps. It is a perennial species with numerous 5-30 cm long stems, stalk less leaves and very attractive pink-purple flowers appearing from July till August. Like other species from family Lamiaceae it is very aromatic, but also rich source of antioxidant polyphenols. M. croatica could therefore be considered as an ornamental plant or as a good candidate for the development of antioxidant food additives. In case of any commercial use of this species, efficient propagation protocol is required. Objective of this study was to establish efficient protocol for micropropagation of M. croatica. One-nodal segments of young stems were placed horizontally or vertically on MS medium supplemented with 3% sucrose and different concentrations of 6-benzilaminopurine (BAP) alone or in combination with 1-naphthaleneacetic acid (NAA). Subcultures were made every 6 weeks. Number of new shoots, their length and callus formation was estimated from at least three replicates each containing nine explants, all in three successive subcultures. Rooting of micropropagated shoots was examined in MS medium supplemented with indole-3-butyric acid (IBA) or indole-3-acetic acid (IAA) in different concentrations. Optimal multiplication, 19 new shoots per explant, was achieved when 1 mg/l BAP was used alone. Mean length of shoots on this treatment was 11 mm and callus formation was minimum. Higher number of new shoots was produced with 2 mg/l of BA, but cali formation in this case was notable which could result with formation of adventive shoots. Explant orientation did not influence number of new shoots. This is caused by explants shortness and consequently by the similar exposure of the buds to the media, regardless of the explant orientation. Efficient rooting (100%) was obtained in hormone free medium, as well as in medium supplemented with IBA up to 1.5 mg/l. Higher concentration of IAA (1 or 1.5 mg/l) produced lower percentage of rooted shoots. When planted in sterile substrate, rooted shoots survived acclimatization with survival rate of more than 90%. We can conclude that efficient micropropagation protocol was developed for M. croatica that is prerequisite for cultivation of this species for any use.

micropropagation; protocol optimization; rooting; Micromeria croatica

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