Evaluation of Biochemical and Antioxidant Characters in Fennel (Foeniculum Vulgare) Ecotypes under Drought Stress

Drought stress is the most important abiotic factor limiting growth in arid and semiarid regions. In this study, the effects of different levels of drought stress on protein content, proline, soluble sugars and the activities of antioxidant enzymes polyphenol oxidase and peroxidase were studied in fennel (Foeniculum vulgare L.). Ten fennel ecotypes were subjected to two levels of water stress including control (maintained by regular watering at or close to field capacity) and drought stress (irrigation at 40% field capacity), in a factorial experiment based on a completely randomized design with three replications. Results of the analysis of variance showed significant differences between the ecotypes for all measured traits except proline. Also, drought stress had a significant effect on all the studied traits. The activities of antioxidant enzymes polyphenol oxidase and peroxidase increased in the leaves of all ten ecotypes at stress conditions. Soluble sugar and proline content in most ecotypes showed a significant increase at drought stress level (irrigation at 40% field capacity). Total protein content in all studied ecotypes showed a significant decrease at drought stress level. The results of ecotypes rating using SIIG method showed that ecotypes Khorshidabad and Tatmaj had the highest SIIG in comparison with other ecotypes and these ecotypes were identified as the most tolerant ecotypes. The ecotypes Shirvan, GhaziAntpet and Izmir were also identified as the most sensitive ecotypes to drought, respectively. Results of ecotypes ranking based on SIIG index had full compliance with the results of cluster analysis based on Ti tolerance index.