Articles
SELECTION OF THYME (THYMUS VULGARIS L.) FOR EXTREME AREAS
This thyme produces also less essential oil than the Mediterranean type and it is more difficult to thin out his leaves.
In order to alleviate these drawbacks, a selection program was started in 1986 at the Centre des Fougères in Conthey (Switzerland). The basic material is a southern type of thyme, of thymol chemotype, originated from the Val d’Aoste, an inner valley in the Italian Alps with a warm and dry climate.
In fact the natural distribution of the species doesn’t spread further to the north than Val d’Aoste.
The thyme is located here from 375 to 1600 m a.s.l., on rocky steppes or in ravines, in the same distribution area than that of the Quercus pubescens. At the present time, it spreads readily in the fallow.
The floral biology of thyme, studied by the French in particular. reveals in Val d’Aoste a distinctive characteristic: the male sterile individuals; generally with small flowers form bigger flowers at high altitude, and also in sites with strong competition.
Also the variability of phenotype is more extensive among male sterile plants that among hermaprodites.
A great variability in hardiness as well as in dry matter and active principles yields were observed in a population of 40 plants collected at 1400 m a.s.l. in the Val d’Aoste and cultivated in the experimental field of Arbaz (920 m a.s.l.), in Switzerland.
Hermaphordite individuals seem more hardy and produce more biomass, but male sterile plants contain apparently more essential oil.
Yields up to 6% essential oil have been observed as well.
For 4 years, clones were observed and hybrids have been created from the best plants of them.
Offspring of these hybrids shows more homogenous phenotypical characteristics.
So sexual multiplication of the hybrid clones could certainly solve the problem of perishing brought by the vegetative propagation, as it is practiced in France in particular.
It should also help to lower costs of production.
This selection program should contribute towards and improvement of the perenniality and of the quality of thyme cultivation in marginal mountain areas.