Evaluation of Root and Shoot Characteristics of Sesame Genotypes under Different Soil Moisture ‎Conditions

In dry regions, root systems play a major role in controlling plant growth and yield, thanks to their importance in water absorption. In order to investigate the effect of irrigation regimes on root and shoot traits of sesame (Sesamum indicum L.) genotypes, a field experiment has been conducted in Karaj, at Seed and Plant Improvement Institute, during 2017 and 2018. A factorial experiment has been laid out in a completely-randomized design with four replications. This study deals with five genotypes of sesame in two irrigation regimes, including full and low (drought stress) irrigation treatments in terms of root and shoot-related traits. Results show that there have been significant differences between genotypes and irrigation regimes for root and shoot traits. In all genotypes, root length density is higher in full irrigation treatment as well as the upper soil layer (0 to 30 cm deep), compared to stress treatment. In addition, under drought stress conditions root depth increases (by 30% in average) in all genotypes. In contrast, root dry weight has decreased in Dashtestan 2 (15 %), Darab 1 (16 %), and Naz (22 %), and increased in Oltan (1 %), USA-ns 96 (7 %), and Sodan 94 (10 ) genotypes. On the other hand, the highest amount of shoot dry weight belongs to the USA-ns 96 genotype (39 g), and the lowest to Naz cultivar (22 g). Finally, results show that USA-ns 96 genotype, being superior in terms of root characteristics such as root depth and root length density compared to other genotypes, in addition to having more shoot dry weight, show the least dry weight loss under stress conditions.