In vitro micropropagation of endangered Rhododendron ponticum L. subsp. baeticum (Boissier & Reuter) Handel-Mazzetti

Abstract

In vitro propagation of Rhododendron ponticum L. subsp. baeticum, an endangered species present in limited and vulnerable populations as a Tertiary relict in the southern Iberian Peninsula, was attained. Several cytokinin:IAA ratios and a range of zeatin concentrations were evaluated for their effect on shoot multiplication from apical shoots and nodal segments. The type of cytokinin and the origin of the explant were the most important factors affecting shoot multiplication. The highest shoot multiplication rate was obtained from single-nodal explants on medium supplemented with zeatin. Increasing zeatin concentration promotes shoot multiplication independently of explant type, although this effect tends to decrease with higher zeatin concentration. Shoot growth was higher in apical shoots and it was not stimulated by the presence of auxin. A number of experiments were conducted to identify suitable procedures for rooting of in vitro produced shoots. The best results in terms of in vitro rooting were obtained with Anderson's modified medium with macrosalts reduced to one-half, regardless of the auxin or its concentration in the medium. Although rooting frequency rose to 97% by basal immersion of shoots in auxin concentrated solution followed by in vitro culture on an auxin-free medium, the survival of the plants after 6 months of acclimatization was poor (50%). Best results (100% rooting and survival) were observed for ex vitro rooting. The micropropagated plants from this study were successfully reintroduced into their natural habitat (87% of survival after 8 months).Abbreviations: 2iP -2-isopentenyladenine; AND -Anderson's medium; BA -6-benzyladenine; IAA -indole-3-acetic acid; IBA -indole-3-butyric acid; Kin -kinetin; MS -Murashige and Skoog medium; 1/2AND -half-strength Anderson macronutrients; NAA -2-naphthalene acetic acid.

The use of in vitro culture to improve the propagation of Rhododendron ponticum subsp. baeticum (Boiss. & Reuter)

“…After 120 days of culture, the explants had grown up to 20 mm and formed an average of 20 new buds and 4 lateral shoots (Table 4). Almeida et al [17] reported higher proliferation rates using zeatin as growth regulator although our results show that BA could be used also at low concentrations and longer periods of culture. Nevertheless, it should be noted that our cultures were not clones as in [17] Our results show that in vitro germination of R. ponticum subsp.…”

“…Almeida et al [17] reported higher proliferation rates using zeatin as growth regulator although our results show that BA could be used also at low concentrations and longer periods of culture. Nevertheless, it should be noted that our cultures were not clones as in [17] Our results show that in vitro germination of R. ponticum subsp. baeticum seeds is easy and effective, allowing high rates of germination in only 30 days from sowing.…”

“…baeticum. Recently, Almeida et al [17] have reported a micropropagation method for this species starting from plants growing in the field. Nevertheless, since a major problem for the survival of this species is the lack of recruitment, it would be advisable to use seeds as starting material in order to introduce biodiversity in the relict populations still existing.…”

Rooting and acclimatization to ex vitro conditions of regenerants of frost-resistant members of Rhododendron

“…В качестве наиболее эффектив-ного стимулятора ризогенеза у микроклонов большинства генотипов используют индолил-3-масляную кислоту (ИМК) (Almeida et al, 2005;Filipenia et al, 2009). Однако размножение in vitro представителей рода осложнено генотипи-ческими различиями морфогенных реакций на всех этапах клонального микроразмножения, включая особенности ризогенеза и адаптации, что особенно ярко проявляется при культивиро-вании листопадных, полувечнозеленых и вечно-зеленых видов и сортов, поэтому выбор того или иного способа применения ИМК определяется экспериментально для каждого генотипа (Briggs et al, 1994;Eeckhaut et al, 2010;Zaytseva et al, 2016).…”

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“…Since it has small numbers of scales, the amount of meristematic cells in the plant is rather restricted. In vitro propagation methods are essential components of plant genetic resources management and they are becoming increasingly important for conservation of rare and endangered plant species (Almeida et al, 2005;Bhatia et al, 2002). The application of tissue culture techniques may allow rapid and large-scale propagation of uniform plants for field condition.…”