Induction of Callus of Two Cultivars from Rice Seed Embryos by the Effect of Abiotic Factors for Drought Tolerance ex Vivo

Abstract

The experiment was conducted at the Plant Tissue Culture Laboratory, College of Agricultural Engineering Sciences, University of Baghdad, during the period 2021-2023, with the aim of inducing Callus from embryos of two rice cultivars: black rice and Amber 33, to enhance drought tolerance in vitro. The Completely Randomized Design (CRD) was applied for experimental arrangements. Different concentrations of 2,4-Dichlorophenoxyacetic acid (2,4-D) (0, 1.5, 3, 4.5 mg L-1) were used to stimulate Callus, along with UV radiation of type UV-C with a wavelength (<280 nanometers), It does not affect the environment because it is absorbed by the atmosphere’s oxygen and ozone, for various durations of 15, 30, 45, and 60 minutes. A control treatment was also used for comparison. The experimental stress conditions were induced using different concentrations (0, 1.5, 3, 4.5, and 6%) of polyethylene glycol (PEG). The fresh and dry weights of Callus were measured for all treatments, in addition to assessing the drought tolerance index. The results showed significant differences for most of the studied traits. The highest fresh and dry weight of Callus was achieved at a concentration of 3 mg L-1 of 2,4-D, at 258.9 mg and 26.06 mg, respectively. The control treatment with UV-C radiation outperformed with the highest fresh and dry weight of Callus, reaching 356.8 mg and 37.81 mg, respectively, compared to other irradiation doses. The control treatment with other PEG concentrations yielded the highest fresh and dry weight of Callus for the cultivars treated with UV-C radiation, reaching 356.4 mg and 38.81 mg, respectively. The drought tolerance index in terms of dry weight, the treatment with 1.5% PEG yielded the highest rate at 0.73 mg, while the treatment with 6% PEG resulted in the lowest rate at 0.21 mg. additionally; the black rice cultivar treated with UV-C radiation outperformed the Amber 33 rice cultivar in terms of both fresh and dry weights of Callus.