The effect of different levels of drought stress on some morphological, physiological and phytochemical characteristics of different endemic coriander (Coriandrum sativum L.) genotypes

Introduction Coriander is an annual herb of the umbel family and is belonged from North Africa to south-western of Asia. Coriander is one of the important medicinal plant that used in the pharmaceutical industry and it mainly cultivated and widely distributed for the fruits. The dried fruits are widely employed as a condiment, especially for flavoring of sauces, meat products and bakery and confectionery items. Also, coriander fruits are as a source of essential oils and fatty oil. Water deficit stress is one of the most important factors limiting the growth and survival of plants in arid and semi-arid regions of the world. Water is a major component of the fresh produce and significantly effects on weight and quality of plants. Also, water deficit may cause significant changes in the yield and composition of essential oils in aromatic and medicine plants. So that, was reported that water deficit increased essential oil percentage in coriander but decreased essential oil yield. Iran with an average annual rainfall of 240 mm is included among arid and semi-arid regions of the world. Of the million hectares of cultivated region, only five millions are under irrigation because of intense water limitations. However, Iran is one of the world’s commercial coriander producers. Coriander has been cultivated for many years in different parts of Iran. Therefore, development of drought-tolerant cultivars with high essential oil yield is important in coriander. This research was conducted in order to evaluate the effect of drought stress on morphological, physiological and phytochemical characteristics of endemic coriander genotypes. Materials and Methods F2 generations derived from half-diallel crosses of six endemic coriander genotypes including Isfahan, Hamedan, Bushehr, Mazandaran, Markazi and Alborz, together with their parents were evaluated in randomized complete block design with three replications in each experiment during growing season of 2016 in the research field of Tarbiat Modares University. Plants were treated with different levels of water treatment: well watered (WW), moderate water stress (MWS) and severe water stress (SWS). Data were collected on plant height, leaf number, branch number per plant, umbel number per plant, fertile umbel number per plant, fruit number per plant, thousand fruit weight, fruit yield, biological yield, essential oil content, SPAD chlorophyll content, relative water content and electrolyte leakage. Results and Discussion The results of ANOVA and comparison of means indicated that the effect of drought stress was significant for all the studied characteristics. The results showed that by increasing drought stress the most studied traits decreased but the essential oil content significantly increased. The highest essential oil content was observed in moderate stress. Studies have, however, indicated that water stress have a number of positive effects on the biosynthesis of secondary metabolites such as essential oil content. Because in case of stress, more metabolites are produce in the plants and substances prevent from oxidization in the cells, but essential oil yield reduce under drought stress. This may because of the relationship between the amount of the essential oil and fruit yield that by progress in drought stress, increase in essential oil but decrease in fruit yield therefore essential oil yield is reduced. Also in the study was used of stress tolerance index (STI) as the best indicators for evaluating of tolerant to drought stress of coriander genotypes. The Mazandaran genotype and crosses derived from this genptype (Alborz Mazandaran, Markazi Mazandaran, Isfahan Mazandaran, Mazandaran Hamadan and Mazandaran Bushehr) were identified as drought tolerant genotypes. Conclusion Generally, the results indicated that drought stress decreased all studied traits. Whereas essential oil content was increased under drought stress conditions. Also, The Mazandaran genotype and crosses derived from this genptype (Alborz Mazandaran, Markazi Mazandaran, Isfahan Mazandaran, Mazandaran Hamadan and Mazandaran Bushehr) as drought tolerant genotypes can be considered as donor parent which contains drought tolerance genes and could be used to improve coriander high essential oil yield in drought condition. Acknowledgements: The authors thank from the Gene bank of the Seed and Plant Improvement Institute of Karaj, Iran for making available plant materials.