Morpho-Physiological and Genetic Responses of Bali Local Rice Cultivars to Drought Stress at Seedling Stage

Rice is the main food source in many countries in the world. One of the major limiting factors for rice growth and productivity is drought stress. In Bali there are several local rice cultivars, two of them are ‘Mansur' and ‘Putih Cempaka'. The cultivar ‘IR 64' is one rice cultivar released by IRRI. The responses of those rice cultivars to drought stress were tested. This study aimed to analyze growth responses and expression of DREB and SOD genes under drought stress induced by PEG. Rice seedlings were grown in a hydroponic system. Two weeks old seedlings were treated with PEG 20% (-0.49 MPa) and 30% (-1.03 MPa) for three days. Root to shoot ratio was calculated and chlorophyll content was measured. RNA was extracted from the shoot. Semi-quantitative real-time PCR was conducted and the products were visualized using 1% agarose gel electrophoresis. The result showed that root to shoot ratio increased as PEG concentration increased in all rice cultivars tested. The chlorophyll content decrease under PEG treatments in all rice cultivars. The expression of Superoxide Dismutase (Cu/Zn-SOD) gene increased under drought treatmentsin ‘Mansur’ and ‘Putih Cempaka’, while in ‘IR64’ using SOD primer tested, the gene was not expressed. The expression of Dehydration-Responsive Element Binding (DREB1) gene increased under PEG treatments both in ‘Mansur’ and ‘Putih Cempaka’.