Evaluation of Biotic Elicitors Foliar Application on Functional Changes, Physiological and Biochemical Parameters of Fennel (Foeniculum vulgare)

Fennel or green badian is one the oldest medicinal plants of Iran, with its different parts are used in drugs, cosmetic and traditional medicine industries. Elicitors' application increases the yield and secondary metabolites production in medicinal plants. Considering the increasing demand and the economic importance of plant metabolites types, the use of biotic elicitors in sustainable agricultural systems is necessary in order to quality improve and the maximum yield and essential oil yield of native medicinal plants of Iran. This research was concluted at the agricultural research istitute of Zabol University in a completely randomized design with three replications and 16 treatments in 2016. In this study, foliar spray of salicylic acid and chitosan were in three stages of vegetative, flowering and reproductive with different combination by sprays. Characteristics of height plant, number of umbrella per plant, number of umbellate per plant, thousand –seed weight, seed yield, biological yield, harvest index, essential oil percentage, essential oil yield, chlorophyll a, chlorophyll b, carotenoid, anthocyanin, flavonoid, phenol, peroxidase and polyphenol oxidase were evaluated. According to the results, increasing chitosan and salicylic acid concentrations increased the number of umbellate and umbrella per plant. The results showed that the highest number of umbrella per plant was obtained from chitosan= 200 mg.l-1, salicylic acid= 1.5 mM (A15) and the lowest value from chitosan= 0 mg.l-1, salicylic acid= 0 mM (A0) treatment. The chitosan and salicylic acid foliar application had a significant effect on thousand –seed weight, so that the treatment chitosan= 150 mg.l-1, salicylic acid= 1.5 mM (A14), increased the thousand –seed weight by 41.1% compared to the control. The highest seed yield was obtained from A15 treatment with the mean of 1551 kg.ha-1 and lowest in control treatment with the mean of 11.22 kg.ha-1, which showed a decrease of 27.7% (480.4 kg) compared to the control. Also, with increasing levels of chitosan and salicylic acid, biological yield and harvest index increased significantly compared to control. The highest percentage (2.86%) and essential oil yield (14.2 kg ha-1) were observed in A14 treatment. Without elicitors application significantly decreased amount of chlorophylls, carotenoids, anthocyanins and flavonoids. The 200 mg.l-1 chitosan and 1.5mM salicylic acid application the phenol, peroxidase and polyphenol oxidase enzym activity increased to 76.3, 71.4 and 55.7% respectively, in comparison with the control. The results showed that the chitosan and salicylic acid spraying by enhancing photosynthesis pigments and soluble osmolites, also protection against the damage of electrolyte leakage, improved the ability plant and increased seed yield of fennel. With regard to this fact that the drought is characteristic feature of the Sistan region, it seems that the integrated application of biotic elicitors at 1.5 mM salicylic acid and 200 mg.l-1 of chitosan increased yield, yield components and secondary metabolites of fennel. Therefore, salisilic acid and chitosan are recommended spraying application for planting and development of fennel and alternative for chemicla fertilizers.