Enhancing the tolerance of local Badui rice (Oryza sativa L.) to salinity stress through a combination of induced variation and in vitro selection

Rice (Oryza sativa L.) is one of the most important food crops, but its productivity is threatened by the widespread conversion of agricultural land. One way to address this issue is to use suboptimal land, such as saline land. However, high soil salinity can significantly reduce productivity. Efforts to address this challenge involve developing salt-tolerant rice varieties using variation induction and in vitro selection methods. This study aims to determine the optimal combination of plant growth regulators (PGRs) for the induction and growth of local Badui rice callus and to obtain a callus that exhibits resistance to salinity stress. Local Badui rice callus was induced on Chu N6 medium with various combinations of PGRs and then selected on salinity stress selection medium with NaCl concentrations of 2500- 7000 ppm. The results showed that the optimal induction medium for callus formation was achieved with the addition of 2,4-D at 2.5 ppm, yielding the highest callus formation rate of 84% and the combination of NAA at 1.5 ppm + BAP at 0.25 ppm resulted in the fastest callus formation at 7.01 days post-planting. Meanwhile, the medium with the addition of 2,4-D at 1 ppm was the optimal callus growth medium, yielding the highest average callus mass and diameter, namely 204 mg and 12.5 mm, respectively. Local Badui rice callus was proven capable of surviving at NaCl concentrations up to 7,500 ppm with a survival rate of 100%.