Isolation and characterization of altered root growth behavior and salinity tolerant mutants in rice

Generation, screening and isolating mutants for any developmental and adaptive traits plays a major role in plant functional genomics research. Identification and exploitation of mutants possessing contrasting root growth behavior and salinity tolerance in rice will help us to identify key genes controlling these traits and in turn will be useful for manipulating abiotic stress tolerance through tilling and genetic engineering in rice. In this study, we have screened about 1500 mutants (M 2 generation) generated by treating an upland drought tolerant genotype Nagina 22 with Ethyl Methane Sulfonate (EMS), for their root growth behavior and salinity tolerance under hydroponic conditions. Six independent mutant lines possessing significantly shorter roots and three mutant lines exhibiting greater degree of salinity tolerance than the wild type plants were identified. The identified mutant lines were advanced to M 5 generation to allow the mutants to reach homozygosity, and the fixed mutants were confirmed for their phenotype. One mutant namely N22-C-241-5-6 was found to possess significantly shorter roots than wild type N22, and it was also noticed that the mutant was devoid of root cap. Among the three salinity tolerant mutant lines identified, N22-C-334-3 was found to possess a greater degree of tolerance upto 250 mM Nacl stress at germination stage. These identified mutant lines can be used for further physiological, biochemical and molecular biology experiments to identify candidate gene(s) controlling root growth behavior and salinity tolerance in rice. Keywords : Rice, mutation, EMS, altered rood growth and salinity tolerant mutant African Journal of Biotechnology Vol. 12(40), pp. 5852-5859