TITLE:
Micropropagation of the Moroccan Endemic Plant Thymus broussonetii Boiss. with Aromatic-Medicinal Value and Conservation Concern
AUTHORS:
Zineb Nejjar El Ansari, Ibtissam Boussaoudi, Rajae Benkaddour, Houda Tahiri, Aïcha El Oualkadi, Alain Badoc, Patrick Martin, Ahmed Lamarti
KEYWORDS:
Thymus broussonetii, Micropropagation, Shoot Tip, Nodes, Macronutrients, Cytokinins, Polyamines, Auxins, Prototypes, Conservation
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.11 No.6,
June
30,
2020
ABSTRACT: Micropropagation from shoot tips and nodal segments
was carried out for the conservation and domestication of spontaneous Moroccan
thyme, Thymus broussonetii Boiss.
subsp. broussonetii (endemic threatened). The mineral composition of the
culture medium, as well as the succession of different growth regulators,
influenced the in vitro growth of
this species. Sterilized achenes of T. broussonetii were able to germinate on an agar medium containing Gautheret
macronutrients with a rate of 25% and a degree of contamination of less than
4%. Shoot apices of 15-day seedlings (two cotyledon leaves) were cultivated on
SD + 0.46 μM Kin medium and the explants obtained were transplanted every
month. Six macronutrients (MS, B5, SH, SD, MSm and N30K) were tested and N30K
was chosen for the following experiments. Seven cytokinins (Kin, BAP, 2iP, DPU,
adenine, Zeat and TDZ) at 0.46, 0.93 and 2.32 μM/l were evaluated and the
addition of 0.93 μM adenine to N30K medium favored significantly the
induction of buds and the elongation of explants. Three polyamines (putrescine,
spermidine and spermine) at 2, 5, 10 and 20 μM/l were tested. A better
multiplication of buds, shoots and roots was noted for N30K + 10 μM
spermine. Cytokinin-auxin combinations led to better root multiplication and an
increase in the number of buds and the length of explants, particularly
for 0.46 μM Kin + 2.85 μM IAA. Acclimatization was successfully carried out
using vitroplants developing a good root system. One month after the start of
acclimatization, 97% of T. broussonetii plantlets were healthy. Three months later, they were transplanted
into larger pots. 100% of the acclimatized plants developed flowers in the 2nd year between June and August. Re-initiation of the in vitro culture was carried out from sterilized twig segments
collected from the acclimatized plants of T. broussonetii with 1 - 2 nodes on the medium N30K
+ 0.46 μM Kin, and 52.1% of the explants healthily proliferated. Finally, two
micropropagation prototypes were developed: shoot tip culture from seedlings
obtained after germination of achenes and node culture from acclimatized
plants.