INDUCTION OF DROUGHT TOLERANCE CAPABILITY OF SOYBEAN THROUGH MANNITOL AND HYDROPRIMING

Abstract

The experiments were conducted at the Agronomy Laboratory, Sher-e-Bangla Agricultural University, during the period from April to May 2018 to investigate the potentiality of seed priming for induction of drought tolerance capability and the pre-sowing seed treatment with mannitol on germination behavior and growth of soybean (BARI soybean 5 and BARI soybean 6) under drought stress conditions. The whole study was divided into three experiments. In the first experiment, two soybean varieties were surface sterilized with 75% of alcohol for 5 min and soaked in water and 2%, 4%, 6%, and 8% mannitol for 6 hours and dry seed used as control. Then the seeds were dried in room temperature to regain normal condition. Seeds primed with 6% mannitol of BARI soybean 6 showed higher germination percentage (96.70%), shoot length (86.92mm), root length (55.44mm), relative water content (95.41%), coefficient of germination (22.82%) and vigor index (137.7) than seeds without priming(control) of BARI soybean 5 in germination percentage (69.00%), shoot length (28.30mm), root length (17.20mm) , relative water content (67.58%), coefficient of germination (15.50%) and vigor index (31.38). In the second experiment, BARI soybean 6 was primed in 3, 6, 9, 12, 15, and 18 hours under both 6% mannitol solution and distilled water, respectively. Priming time 6 hours with 6% mannitol showed the best result for increasing the effectiveness in inducing drought tolerance in all parameters except WSD (water saturation deficit). In the third experiment, seeds were primed with distilled water and 6% mannitol for 6 hours and primed seeds were placed under control and drought stress condition induce by 5% PEG,10% PEG, 15% PEG and 20% PEG solution in Petri dish. Drought tolerance capability increased in osmopriming over hydropriming. These result suggest that soybean seeds primed with 6% mannitol for 6 hours showed the best result than hydropriming. This priming concentration and time helps to induce drought tolerance capability of soybean and also helps to enhance germination, growth of seedlings and water relation behavior under such stress conditions.