Effect of water potential on seed germination indices of six Sesame cultivars (Sesamum indicum) at different temperatures and its relation to fatty acid composition

Knowing the optimum temperature and base potential for each seed is an important step in better germination, increasing uniform emergence and chances of plant establishment. To evaluate the effects of water potential on seed germination indecies of six sesame cultivars in different temperatures and their relations with fatty acids content, the experiment was conducted as factorial based on a completely randomized design in four replications in 2018 at the Seed Technology Laboratory of Yasouj University of Agricultural College. The first factor consisted of six sesame varieties named Halil, Darab 1, Dashtestan 2, Oltan, Yellow White and Naz Single Branch and the second factor consisted of seven water potential levels (-0, -0.2, -0.4, -0.6, -0.8, -1 and -2.2 MPa), which were tested at eight temperature levels (10, 15, 20, 25, 30, 35, 40 and 45 °C). The results showed that different cultivars of the same species can exhibit different responses to environmental conditions. With decreasing water potential, seed germination indices decreased. The highest percentage and rate of germination (57.3%, 0.33 seed/day) were observed at an optimum temperature of 25 °C. Dashtestan 2 and Yellow White had the highest (65%) and the least (53%) oil content, respectivly. Oleic and linoleic fatty acids were the most unsaturated fatty acids in the seeds of all six sesame cultivars, and the relationship between germination rate and unsaturated fatty acids, showed that for oleic and linoleic acid by certain concentration (about 43%) increased the germination rate. According to the results, the cultivar Halil can be considered for warmer regions and the Naz Single Branch cultivar for cooler regions. Among cultivars, Dashtestan 2 had the best germination under stress conditions, which is a more suitable cultivar than other cultivars in hot and dry areas.