Intraspecific variation in oil components of Boronia megastigma Nees. (Rutaceae) flowers

Intraspecific variation in the oil composition of Boronia megastigma Nees. (Rutaceae) was examined. Boronia absolute is extracted from blossom primari ly for use as a food additive. A major component is beta-ionone and B. mega stigma is one of the commercial, natural sources of this compound. Genotype s superior in production of beta-ionone and low in monoterpene hydrocarbons were sought from natural populations in the south west of Western Australi a as part of a breeding programme. Flowers were collected from 25 plants in each of 29 different populations. Blossom was extracted with ethanol and a nalysed using a gas Liquid chromatograph fitted with ionisation detectors. The contents of beta-ionone, dodecyl acetate, alpha-pinene, beta-pinene and limonene in the oil extract were compared. Intrapopulation Variation was a s great as inter-population variation and no distinct chemotypes were found . Considerable variation existed in the content of components. The highest beta-ionone content was 1787 mg g(-1) f. wt. Some genotypes contained all f ive components analysed, others lacked one or more of the monoterpenes: alp ha-pinene, beta-pinene or limonene. Principle components analysis indicated that contents of beta-ionone and dodecyl acetate were associated and that they were distinct from the content of the monoterpenes, which were associa ted with each other. Natural shading was associated with lower levels of mo noterpenes but other oils were unaffected. Young. plants contained less pin enes than older plants and old plants contained the most dodecyl acetate. V igorous plants produced more pinenes. Red flowers contained the least beta- ionone and dodecyl acetate. (C) 1999 Annals of Botany Company.