Investigation of the effect of drought stress on yield and yield components ofCuminum cyminum L. ecotypes in climatic conditions of Kerman Province

Cumin (Cuminum cyminum L.) is one of the most important medicinal plants, with a short growth period and low water requirement, suitable for cultivation in arid and semi-arid regions of Iran. Drought is one of the most important factors limiting plant growth worldwide and the most common environmental stress. In the case of medicinal plants, drought may have a noticeable effect on the yield and amount of active ingredients. In order to investigate the drought tolerance of cumin crop ecotypes, a split-plot experiment was conducted in the form of a randomized complete block design with three replications at the Agriculture and Natural Resources Research and Education Center in the crop year 2019-1400. In this study, the effect of drought stress at three levels (normal irrigation, interruption of irrigation after 50% flowering of the field, and interruption of irrigation after 100% flowering of the field) on five cumin ecotypes (Mahan, Kohbanan, Khosuf, Kashmer, Sabzevar) was investigated. The results of the analysis showed the effect of ecotype and stress separately and together on all investigated traits such as plant height, number of umbels per plant, umbrella number per umbrella, seeds number per plant, harvest index, number of secondary branches, seed yield, biological yield, straw weight and stubble and the percentage of seed essential oil were significant at the five percent level. The highest seed yield and percentage of essential oil in the Khosuf ecotype were obtained under stress-free conditions and irrigation interruption after 50% flowering of the field, respectively. The regression results in all three irrigation conditions showed that the number of umbels, umbrellas and the number of seeds per plant can lead to the highest yield and are the most important factors in determining seed yield.