In vitro screening of rice (Oryza sativa L) callus for drought tolerance

While drought resistance is become of increasing importance in rice (Oryza sativa L.), selection under actual field conditions is tedious due to low heritability and time required. Selection in tissue culture is thought to be one way to improve selection efficiency, but this requires standardized protocols. Rice cultivars PAU 201 and PR 116 showed significant callus induction, but the capacity for callus induction and regeneration decreased under polyethylene glycol (PEG) (6000) stress in both cultivars. Calli were induced on semisolid Murahige and Skoog (MS) medium supplemented with 2.5 mg l-1 2, 4-dichlorophenoxy acetic acid (2,4-D) + 0.5 mg l-1 kinetin (kin) + 560 mg l-1 proline + 30 g l-1 sucrose + 8 g l agar-1. Embryogenic calli showed shoot regeneration on MS medium supplemented with 2.0 mg l-1 benzyl aminopurine (BAP) + 0.5 mg l-1 kinetin + 0.5 mg l-1 napthalene acetic acid (NAA) + 30 g l-1 sucrose + 8 g l-1 agar. Increased levels of PEG (6000) (0, 0.5, 1.0, 1.5, 2.0 %) were used to create water stress. There was reduction in callus induction ability and plant regeneration efficiency with increasing levels of PEG (6000) stress. These results indicated that PEG (6000) can be used as water stress creating agent under in vitro conditions and rice variety PR 116 was relatively tolerant to drought stress as compared to PAU 201. This study will serve as a base line for in vitro screening of drought tolerant transgenic rice.