CHARACTERISTICS OF VARIETIES OF THYME (THYMUS-VULGARIS L) FOR USE IN THE UK - OIL CONTENT, COMPOSITION AND RELATED CHARACTERS

This paper describes the first stage in a programme for the selection of varieties of thyme (Thymus vulgaris L.) with improved potential for volatile oil production, from seedlots of varieties which had been developed for use as ornamentals. The variation within and between varieties in the following characters was assessed over two seasons in isolated field plots (16.5 m x 18.5 m) at Auchincruive: dry matter yield per plant; oil content of leaf fraction; oil yield per plant; chemical composition of oil; plant shape; timing of reproduction; and reproductive type (hermaphrodite or male sterile). Variation in leaf oil content and in leaf dry matter production per plant was generally greater within than between varieties, but oil composition (> 50% thymol) was very similar throughout the materials tested. It was concluded that screening for individual plants with high dry matter production followed by analysis of tissue oil content was a simple and economic method of identifying plants with high potential for oil production. The commercial exploitation of selections of this kind will depend upon improved understanding of the heritability of leaf oil content, and of interrelationships among oil composition, reproductive type and ontogeny.