In vitro screening of rice genotypes for drought tolerance using polyethylene glycol

The aim of the present investigation was to study in vitro somatic embryogenesis and to screen calli for drought tolerance using mature embryos as explants. Mature embryos of three aromatic (Pusa Basmati 1, Pant Sugandh Dhan 17, Taraori Basmati) and one non-aromatic (Narendra 359) indica rice (Oryza sativa L.) varieties were used for developing callus on Murashige and Skoog medium supplemented with 2, 4-dichlorophenoxy acetic acid (2, 4-D) (2.0 mg l⁻¹ for Narendra 359 and 2.5 mg l⁻¹ for Pusa Basmati 1, Taraori Basmati and Pant Sugandh Dhan 17). Screening of calli was done by sub-culturing calli for 15 days on Murashige and Skoog (MS) basal medium supplemented with different concentrations of polyethylene glycol (PEG)-6000 as chemical drought inducer. Callus volume decreased and total proline content was found to be increased significantly with increase in PEG concentration. Narendra 359 showed best response in terms of callus growth at 70 g l⁻¹ of PEG. The highest percentage somatic embryogenesis among selected calli was observed in Pusa Basmati 1 and the lowest in Pant Sugandh Dhan 17. Excellent shooting and rooting (94%) was observed in MS + 0.1 mg l⁻¹ naphthalene acetic acid (NAA) and MS + 2.0 mg l⁻¹ 2, 4-D. Regenerated plants were successfully acclimatized with 98% efficiency in greenhouse and grown under pot conditions up to maturity. It was observed that PEG treated somaclones accumulated more proline, chlorophyll content and developed more tiller and height than normal somaclones. Ten random amplified polymorphic DNA (RAPD) primers were used to amplify genomic DNA of somaclones of different varieties. Level of genetic polymorphism existing among these somaclones indicates that these markers can be used in breeding program for improving varieties through in vitro techniques.