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Abstract: The volatile phenylpropenes estragole and t-anethole are the major constituents of the oleoresin of the aerial parts of bitter fennel (Foeniculum vulgare Mill. var. vulgare, Apiaceae). The levels of estragole and t-anethole varied during plant development, being maximal in flowers and developing mericarps. Still the ratio between estragole and t-anethole remained constant throughout development. Estragole-rich types were hybridized with t-anethole rich types to examine the genetic basis of this polymorphism. A reverse correlation between estragole and t-anethole content was evident and the action of a biallelic gene with partial dominance for high estragole content was inferred. Understanding phenylpropene inheritance might explain chemical polymorphism in wild bitter fennel populations, sheds light on the molecular mechanisms that lead to chemotypes evolution and is crucial for breeding fennel varieties with desired chemical compositions. [Copyright &y& Elsevier]

Bitter fennel (Foeniculum vulgare Mill. var. vulgare, Apiaceae) is a hemicryptophyte native to the Mediterranean basin and cultivated for its use as a medicinal and spice. We describe here the flowering dynamics and crossability among six native populations of bitter fennel collected from four localities in Israel, one from Sinai Desert (Egypt), and one from Mersin (Turkey) and grown from under agricultural conditions. Timing and duration of the stigma's receptivity were evaluated morphologically, enzymatically, and by determining fruit set in response to artificial pollination. Self-compatibility rates and crossability within and between populations were also determined in response to artificial pollination. Although the populations initiated flowering at different times through the season, in all cases the stigma's receptivity peaked between six and eight days after anthesis (yellow-bud stage) and lasted for seven days. Pollen can primarily germinate on the stigmata but the stylopodium serves too as a site for pollen germination, albeit at a lower efficiency (0-10% fruit set) as compared to stigmata (25-54%). Although there is complete dichogamy within flowers, umbels, and branches, there in not enough dichogamy between branches, and geitonogamy is therefore possible. Additionally, all populations displayed a high (0.7-3.7) index of self-compatibility (ISI), indicative of substantial self-pollination. Although interbreeding among populations was proven using artificial pollination, geographical isolation and the high likelihood for self-pollination probably restricts gene flow and contributes to the phenotypic diversity observed in wild fennel populations. [ABSTRACT FROM AUTHOR]

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. [Copyright &y& Elsevier]