In vitro Salt Tolerance Screening in Long-Term Anther Cultures of Rice ( Oryza sativa L.) Variety IR 50

Abstract

Summary Combinations of plant growth regulators and sugars to achieve maximum callus induction and longterm plantlet regeneration from anther cultures of a high yielding rice ( Oryza sativa L.) variety IR 50 were assessed to enable effective screening of salt-tolerant genotypes. Callus induction was found to be maximal when 2,4-dichlorophenoxyacetic acid (9.1μM) and kinetin (2.3μM) were used as a supplement on N6 basal ( Chu et al., 1975 ) induction medium. For long-term maintenance, callus was subcultured on MS ( Murashige and Skoog, 1962 ) basal medium supplemented with 2% sucrose, 3% sorbitol, and 4.5μM 2,4-dichlorophenoxyacetic acid. For regeneration, MS basal medium was supplemented with 9.3μM kinetin, 2.7μM naphthaleneacetic acid, 2% sucrose, and 3 % sorbitol. Salt-tolerance screening of anther callus in a range of salt concentrations (0 to 1.5% NaCl) for 1 or 2 passages suggested i) that higher concentrations of NaCl (0.9 to 1.5 %) in the stress medium reduced callus survival and increased frequency of albino plants even after one passage and ii) that lower concentrations of NaCl (0.3 to 0.6%) resulted in almost equal proportions of green and albino plants, and iii) that the fresh mass and water content of callus were drastically reduced at higher salt concentrations. Assessment of the screened regenerants indicated that the variations were epigenetic in nature. We conclude that long-term culture maintenance without loss of green plantlet regeneration, and screening anther callus at semi-lethal salt concentrations of 0.3 to 0.9% NaCl will be optimum for isolation of both genetic and epigenetic variants of rice.