Effects of drought stress on performance and yield and other traits of different ecotypes of fennel (Foeniculum vulgare L.)

To evaluate the effects of drought stress on the changes of yield and other traits of different ecotypes of fennel, a field experiment was conducted which was organized in split plots in the form of completely randomized blocks. The main treatment was irrigation with three levels of 80, 140, and 180 ml of evaporation from the A-class evaporation pan which represented normal irrigation, mild drought stress, and severe drought stress, respectively. The constant factor was comprised of 51 ecotypes of fennel. Results showed that a mild drought stress can enhance essential oil content in seeds. The experiment also demonstrated that different levels of irrigation had significant impacts on total dry weight of aerial parts of the plant (in the five percent statistical level). The impact was also significant on total yield of seed, weight of 1000 seeds and essential oil content (in the one percent statistical level). Mean comparison results revealed that the highest seed yield belonged to the treatment group with the normal irrigation level. Means comparison results also showed that the highest seed yield belonged to the Alamout ecotype whereas the least seed yield belonged to the Tafresh and Yazd ecotypes. The comparison of means with regard to the effect of irrigation levels on essential oil content showed that the highest essential oil content was achieved at the mild stress treatment. The interdependent effects of irrigation levels on ecotypes had a significant impact on the total dry weight of the aerial parts of the plant based on the 5% significance level. However, the interdependent impact on the amount of essential oil was significant at 1% significance level. Mean comparison regarding the interdependent effects showed that the highest essential oil content was achieved in the Meshkin-shahr ecotype while treated with mild drought stress.