Ontogenetic and trans-generational variation of essential oil composition in Agastache rugosa

- Variability of Agastache rugosa progeny essential oil composition is influenced by the mother plant age .
- Older plants obtained from seeds of 2- and 3-year old plants provide higher quality essential oil rich in methyl chavicol.
- Oil distilled from inflorescences contain higher amount of pulegone and less methyl chavicol than oil from leaves.

Agastache rugosa is an important medicinal and aromatic crop cultivated in East Asia and an ornamental in other temperate regions. The factors influencing the diversity of volatile profiles in this and many other aromatic plants remain largely undiscovered. In this study, a relationship between the age of mother plants and the volatiles profile of the progeny was investigated using Gas Chromatography-Mass Spectrometry, both in plants cultivated conventionally for three years and in vitro shoot cultures.The essential oil contains a major phenylpropanoid methyl chavicol (estragole) as well as minor mono- and sesquiterpenoids but the composition is very variable. The variability of composition in the progeny was indeed different in plants obtained from seeds coming from one-, two- and three-year old parents but also between young (one-year-old) and older (two- and three-year-old) plants. The quantitative variation among individuals was mainly in the content of methyl chavicol (from ca. 1% up to over 90%), menthone/isomenthone pair in leaves (from traces to 59%), and additionally pulegone (traces to 51%) in inflorescences. Limonene was least variable averaging between 8% and 25%. The variability tended to decrease and the proportion of methyl chavicol increased along with the age of parent plants. Two- and three-year-old plants were also producing higher yields of essential oil with average of 2.1% and 2.6%, respectively, compared with 1.2-1.9% in one-year old plants.In conclusion, the comparative analysis of essential oil and headspace revealed that volatile organic compounds profile of A. rugosa was dependent on the age of parent plants.

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