Turkey is one of the richest countries in variability of flora. It has nearly 9000 plant species about 3000 of which are endemic [1]. Asteraceae, is represented by 50 species in Turkey with an endemism of nearly 54% [2]. Rhaponticoides mykalea (Hub.-Mor.) M.V. Agab. & Greuter which belongs to the Asteraceae family, falls within the CR (Critically Endangered) category in the Red Data Book of Turkey [1]. While R. mykalea (Hub.-Mor.) was classified under the section Centaurea as Centaurea mykalea (Hub.-Mor.) before now. Today it has been separated from the section Centaurea [3]. It spreads very scarce in Kuşadası (Aydın), Muğla and Isparta, and faces with the danger of extinction. R. mykalea that has very limited number of individuals is under strong anthropogenic pressure such as the gradually increase in ongoing urbanization due to rapid developments of tourism sector, the conversion of natural habitats into human dominated lands, the over-grazing and collecting capitula of R. mykalea by local people for food. The species has already been under the threat of extinction and the situation above will increase the risk of extinction of this species even more [4]. For this reason, local protection measures and global conservation strategies are necessary [5].
Nowadays, the conservation of wild plant genetic resources is very important for preventing a decrease in genetic variability. Conservation of the endemic or threatened plants is carried out using different strategies. In vitro culture is an
efficient method for ex situ conservation of plant diversity [6,7], because many endangered species can be quickly propagated and preserved from a minimum of plant material with low impact on wild populations with this technology [8]. In recent years, there has been an increased interest in in vitro techniques that offer powerful tools for germplasm conservation and the mass multiplication of many threatened plant species [9]. Especially in vitro propagation of endangered plants can offer considerable benefits for the rapid cultivation of at risk species that have a limited reproductive capacity and exist in threatened habitats [5].
Micropropagation constitutes a powerful tool for ex situ conservation programs of threatened plants, especially for species with very reduced populations or low seed production [6,7]. This technique facilitates the rapid establishment of a large number of stock plants, from a minimum of original plant material, thus imposing minimum impact on the endangered wild populations. Axillary shoot proliferation typically results in average tenfold increase in shoot number per monthly culture passage. In a period of 6 months, it is feasible to obtain as many as 1 000 000 propagulesor plants, starting from a single explant [10].With this technology various endemic and endangered species have been successfully propagated; such as and Centaurea paui [8], Anthemis xylopoda O.Schwarz [11], Centaurea spachii [12], Centaurea zeybekii [13], Centaurea junoniana [14], Astragalus chrysochlorus [15], Centaurium rigualii [16] and Syzygium alternifolium [17].
However, during our literature search, no report concerning in vitro regeneration of R.mykalea by axillary shoot proliferation was found.
The objective of the present study was to establish an efficient in vitro method for the rapid propagation via axillary shoot propagation of R.mykalea, a critically endangared endemic plant species. The shoots that were obtained from in vitro germinated mature embryos were used for axillary shoot proliferation. For that reason, the most appropriate cytokinin type and concentration were determined.
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