Chemotypes and morpho-physiological characters affecting essential oil yield in Iranian cumin landraces

The cumin essential oil is used in the food and pharmaceutical industry. Despite the large commercial production of cumin in Iran, there is no comprehensive study on quality and quantity of its essential oil. This experiment was conducted to study morpho-phenological and physiological characters affecting essential oil yield and to identify possible chemotypes in Iranian cumin landraces. Eyvanekey landrace with the highest essential oil content and yield had the highest carotenoids and total chlorophyll contents and oil body number in the cell. The results of the GC-MS chromatography showed that the identified components were classified into four organic compounds including monoterpenes, oxygenated monoterpenes, sesquiterpenes and others. According to essential oil compositions, cumin landraces were clustered in two chemotypes including low cuminal / high monoterpenes and high cuminal / low monoterpenes chemotypes, indicating a significant difference in essential oil quality. Khansar landrace with the highest cuminal content was introduced as the best Iranian landrace in terms of essential oil quality. Neronine alkaloid was identified in cumin essential oil for the first time, and Jat landrace is a novel plant source of neronine alkaloid. Essential oil yield had the positive regression and correlation coefficients with SWM (seed weight per m(2)) and days to maturity which indicate that these characters are suitable selection indexes to improve cumin essential oil yield. A negative relationship between the cuminal content and limonene synthase gene expression (r =-0.55') was observed. So, it was concluded that landraces having low limonene synthase gene expression are favorable for marketing.