Introduction
The oldest evidence of medicinal plant usage goes back to 60,000 years
ago to Kurdistan in Shanidar cave (Lietava, 1992). Bitter fennel is one
of the oldest medicinal plants that due to possessing certain
metabolites, is used as flavoring agents in food and beverages, and as
curative agents in pharmaceutical products (Hornok, 1992).
Bitter fennel (Foeniculum vulgare var. Vulgare ), hereafter
just fennel, as the source subspecies for fennel-derived drugs,
originated from Mediterranean regions, but now has been naturalized in
many other regions (Hornok, 1992). Fennel produces several valuable
phytochemicals in the seeds. One group of these compounds is fatty
acids, also called fixed oils, or just oil (Hornok, 1992).
Plant-based oils are considered heathier than animal-based oils due to a
lower ratio of omega-6 to omega-3 fatty acids, and a higher ratio of
monounsaturated to polyunsaturated and saturated fatty acids (Vidrih, et
al., 2009). Exploring new crops as complementary or substituting sources
of fatty acids to the current main oil crops, including soybeans,
sunflower, canola (FAO, 2018), is valuable for meeting market demand,
and diversifying our oil production sources. Currently, species within
the family Apiaceae are gaining a lot of attention as potential sources
of fatty acids. Among Apiaceae species, fennel is a candidate as a new
source of fatty acids, due to its suitability for mechanized mass
production, high seed yield potential (400-3000 kg/ha), and high fatty
acid content (12-20% of seed mass) (Matthaus and Ozcan, 2015; He and
Huang, 2011; Cosge et al., 2008; Gupta et al., 1995; Reiter, et al.,
1998).
Seeds are the main storage location of fatty acids in fennel, and they
can contain from 3 to 20% oil with the major fatty acids being C18:1
isomers (25-83%), C18:2 or linoleic acid (1-17%), C16:0, or palmitic
acid (0-13%), C14:0 or myristic acid (0-6.5%), C18:3(N3) or linolenic
acid (0.3-4%), C18:0 or stearic (0.8-1.9%), and C20:0 or arachidic
acid (0-0.4%) (Rezaei Chiyaneh et al., 2020; Hayat et al., 2019; Sayed
Ahmad et al., 2018; Agarwal et al., 2018; Rebey et al., 2016; Nguyen et
al., 2015; Acimovic et al., 2015; Bogdanov et al., 2015; Barros et al.,
2010; Vidrih, et al., 2009; Cosge et al., 2008; Singh et al., 2006;
Gupta et al., 1995; Reiter et al., 1998). Petroselinic acid (18:1-cis6),
oleic acid (18:1-9cis), and vaccenic acid (18:1-11cis) are three
positional isomers of C18:1, which can make separation and
quantification cumbersome, but petroselinic acid is the major isomer
(Reiter et al., 1998). Both oleic acid and linoleic acid are essential
fatty acids with many health benefits in human nutrition, and numerous
usages in various industries (Sales Campos et al., 2013; Simopoulos,
2008). The high concentration of oleic acid (77-83% of seed mass) in an
Iranian fennel genotype in different intercropping systems was reported
by Rezaei Chiyaneh et al. (2020).
According to our previous studies on Iranian fennel landraces, there is
significant genetic diversity (Bahmani et al., 2012 and 2013) and
agro-morphological variation among fennel landraces for maturity habit,
seed yield, and essential oil yield composition (Bahmani et al, 2015 and
2016). In terms of maturity habit, Iranian fennel landraces are divided
into early, medium, and late maturity landraces (120, 180, and 230 days
to harvest time, respectively). Little is known about variation in fatty
acid content or composition among Iranian fennel landraces. Therefore
the objectives of the current study were to 1) evaluate potential oil
production in Iranian fennel landraces, 2) evaluate their oil
compositions, 3) identify high potential landraces.