Characterization of fennel germplasm for physiological persistence and drought recovery: Association with biochemical properties

In the perennial medicinal plant fennel (Foeniculum vulgare), persistence over years, production stability, and successful post-drought recovery are as important as plant productivity. Characterization of productivity, post -drought recovery, persistency and their association with phytochemical properties has not yet been performed in fennel. In this study, 64 fennel genotypes (from 23 different countries) from four subspecies/varieties including F. vulgare ssp. piperitum, F. vulgare var. vulgare and F. vulgare var. dulce and F. vulgare var. azoricum were evaluated in the field over four years (2015-2018), then was assessed for post-drought recovery over the next two years (2019-2020). High genotypic variation was observed among genotypes and subspecies. Based on the GC-MS analysis, trans-anethole (22.4-90.6%), estragole (2.1-25.8%), fenchone (4.9-19.8%), and limonene (0.5-11.9%) are major components in the essential oils of the studied germplasm. The highest persistence and the lowest average post-drought recovery belonged to ssp. piperitum. This subspecies also had the highest amount of limonene, fenchone, and estragole and the lowest amount of trans-anethole compared to other subspecies. The highest essential oil content and stability was observed in var. dulce. Seed yield and persistence were found to be negatively associated, suggesting that selection for more productivity may indirectly promote less persistent genotypes. Post-drought recovery was negatively associated with two main phytochemical compounds of essential oil, fenchone and estragole, but positively associated with trans-anethole. Persistence had negative correlation with estragole content. Results indicated that indirect selection for post-drought recovery and persistence may be possible through selection for phytochemical properties. The negative correlation between some essential oil components may indicate that some are isomers, which can limit the ability to select for certain combinations. Superior genotypes identified in this study can be used to construct populations for future studies and as parents of crosses to develop new varieties.