Effect of Irrigation Regimes on Yield, Yield Components and Characteristics Criteria of Essential Oil Percentage of Cumin (Cuminum cyminum L.) Ecotypes in Afghanistan

Cumin (Cuminum cyminum L.) is a small annual herbaceous and an aromatic and medicinal plant included in the Apiaceae family. This plant also possesses resistance to drought stress, which is especially important, considering water deficits in many locations in semi-arid environments. Cumin is used to flavor foods, added to fragrances, and medicinal preparations. Seeds are is yellow to brownish-gray in color. Cumin seeds contain numerous phytochemicals that are known to have antioxidant, carminative and anti-flatulent properties. This spice is an excellent source of minerals like iron, copper, calcium, potassium, manganese, selenium, zinc and magnesium. It also contains very good amounts of B-complex vitamins such as thiamin, vitamin B-6, niacin, riboflavin, and other vital anti-oxidant vitamins like vitamin E, vitamin A and vitamin C. The seeds are also rich source of many flavonoid phenolic anti-oxidants such as carotenes, zeaxanthin, and lutein.
The main objective of this study was to investigate the qualitative and seed yield response of three local ecotypes of cumin as an important medicinal plant to different irrigation regimes under the climatic conditions of Herat, Afghanistan. This experiment was conducted as a split plot experiment based on a randomized complete block design with four replications during growing season 2009-2010 in Herat (Afghanistan) University Research Farm. Treatments were irrigation regimes (main plot) at 4 levels including (rainfed: W1, after stem elongation: W2, early flowering: W3 and early seed formation: W4) and landraces (as subplot) (Rajasthan of India: V1, Badghis of Afghanistan: V2, and Kashmar of Iran: V3). Studied traits were including quantitative traits such as content and yield of essential oil, seed yield, plant height, number of umbels per plant, number of seeds per umbel, lateral shoots, 1000-seed weight, harvest index and the qualitative characteristics including active ingredients in essential oils of cumin.
The treatments were run as an analysis of variance (ANOVA) to determine if significant differences existed among treatments means. Multiple comparison tests were conducted for significant effects using the Duncan’s test. Results showed that simple effect of irrigation regimes and landraces and their interaction had difference significant for content and yield of essential oil, seed yield, plant height, number of seeds per umbel, lateral shoots, 1000- seed weight, harvest index, cumin aldehyde and p-cymene percent at 1% and 5% and the W3 treatment and Indian landrace in terms of most traits was superior, but the greatest number of lateral branches, obtained from V2. However, W4 and W1 treatments showed the highest harvest index percent and number of lateral branches respectively. Most of cumin aldehyde was obtained from Iran and Afghanistan landraces (respectively 27.348% and 25.725%) and highest p-cymene (25.811%) of the interaction of V1 with W4 treatment. The results for correlation coefficients between seed yield, biomass and yield components revealed that there was a positive and negative correlation between these criteria. The highest coefficient was calculated for seed yield and biomass (r=0.926**). Agronomic management strategies had significantly effect on growth, yield, and yield components of cumin ecotypes. The results showed that Indian landrace and W3 treatment are recommended under Heart-e (Afghanistan) conditions. Considering water deficit that the world will face in the future, cumin in those environments susceptible to water stress conditions will have higher water use efficiency compared to other plants.