Gross, M., Newe ya'Ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Iceland, Department of Plant Sciences, G.S. Wise Faculty of Life Sciences, Tel Aviv University, Israel, Department of Biology, Academic College of Education, The Kibbutz Movement, Oranim College, Tivon 36006, Iceland
Friedman, J., Department of Plant Sciences, G.S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
Dudai, N., Newe ya'Ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Iceland
Larkov, O., Newe ya'Ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Iceland
Cohen, Y., Department of Plant Sciences, G.S. Wise Faculty of Life Sciences, Tel Aviv University, Israel
Bar, E., Newe ya'Ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Iceland
Ravid, U., Newe ya'Ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Iceland
Putievsky, E., Newe ya'Ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Iceland
Lewinsohn, E., Newe ya'Ar Research Center, Agricultural Research Organization, P.O. Box 1021, Ramat Yishay 30095, Iceland

Estragole and t-anethole are the major constituents of the essential oils of bitter fennel chemotypes (Foeniculum vulgare Mill. var. vulgare. Apiaceae). Cell-free extracts from bitter fennel tissues display O-methyltransferase activities able to in vitro methylate chavicol and t-anol to produce estragole and t-anethole, respectively, by utilizing S-adenosyl-L-methionine as a methyl group donor. Analysis of different plant parts of an estragole-rich chemotype, indicated an association between estragole accumulation and chavicol O-methyltransferase activity during development. Young leaves displayed higher levels of O-methyltransferase activity than old leaves. In developing fruits O-methyltransferase activity levels increased until the wasty stage was reached and then dramatically decreased. This chemotype also displayed t-anol O-methyltransferase activity at higher levels than chavicol O-methyltransferase activity although these tissues accumulate mainly estragole. O-methyltransferases activities extracted from a high-t-anethole fennel chemotype also methylated t-anol and chavicol at comparable rates. Thus, although the chemotypes greatly differ in their phenylpropenoids composition, both are efficient in in vitro forming t-anethole and estragole. © 2002 Elsevier Science Ireland Ltd. All rights reserved.