In vitro screening and regeneration of water stress tolerant culture of tomato

Callus of tomato (Lycopersicon esculentum Mill.) was initiated from hypocotyls on MS medium supplemented with 3 mg l⁻¹ BAP + 0.50 mg l⁻¹ NAA. For proliferation of callus the hormone concentrations were reduced to half. Cell clumps of about 1mm diameter were exposed to increasing concentrations of polyethylene glycol (PEG-6000) ranging from 10 g l⁻¹ to 100 g l⁻¹ for water stress tolerance. Upon incubation for 40 days the cells, which could tolerate this concentrations of PEG, grew to form calli. Selected calli were further subcultured on the selective medium for proliferation. The selected calli when transferred from the normal to the selective medium, were capable of growing on it. The shoot regeneration from the in vitro selected water stress tolerant calli was obtained in MS medium supplemented with 100 g l⁻¹ PEG + 2 mg l⁻¹ BAP+ 1 mg l⁻¹ IAA. The in vitro regenerated shoots were transferred on MS medium supplemented with 100 g l⁻¹ PEG + 1.25 mg l⁻¹ BAP for shoot elongation. High percentage of root regeneration from in vitro regenerated shoots was obtained in MS medium supplemented with 100 g l⁻¹ PEG + 0.1 mg l⁻¹ NAA.