Genetics, genomics and breeding of fennel

Abstract

Fennel (Foeniculum vulgare Mill. or Anethum foeniculum) stands out as a versatile herb whose cultivation spans across various regions worldwide, thanks to its adaptability to diverse climatic conditions. Its economic importance is mainly due to its numerous pharmaceutical properties and its widespread use in culinary applications. In this review, we first reviewed the chemical composition of this species, stressing the importance of two volatile compounds: t-anethole and estragole. The few cytological and genetic information available in the scientific literature were summarized. Regarding this latter aspect, we pointed out the almost complete absence of classical genetic studies, the lack of a chromosome-level reference genome, and the shortage of adequate transcriptomic studies. We also reviewed the main agronomic practices, with particular emphasis on breeding schemes aimed at the production of F1 hybrids and synthetic varieties. The few available studies on biotic and abiotic stresses were discussed too. Subsequently, we summarized the main studies on genetic diversity conducted in fennel and the available germplasm collections. Finally, we outlined an overview of the main in vitro regeneration techniques successfully applied in this species.

Keywords: Biochemistry; Breeding; Fennel; Genetics resources; Genomics; Molecular markers.

Fig. 1

A Foeniculum vulgare plastidial genome representation (GenBank accession ON641350.1); this panel has been drawn by uploading in Geneious 11.1.4 software (http://www.geneious.com) the cpDNA fasta sequence and its corresponding GFF3 file. B Dot plot analysis among three cpDNA fennel accessions (i.e., NC_029469.1 for USA, KR011054.1 for China, and ON641350.1 for Portugal); the collinearity analysis was performed through the online tool D-genies [22] and the Minimap2 v2.26 aligner. C List of 14 non-synonymous SNVs (Single Nucleotide Variants) found aligning the five-cpDNA sequences available in GenBank for fennel (i.e. NC_029469.1, OM307067.1, ON641373.1, ON641350.1, ON641289.1). The alignment was performed using LASTZ at default parameters whereas SNV calling (minimum variant frequency = 0.2) was achieved in Geneious 11.1.4 software

Fig. 2

Simplified breeding schemes describing the development of F1 hybrids through the exploitation of a cytoplasmic male sterility (CMS, A) and the constitution of synthetic varieties (B) in fennel