SODIUM CHLORIDE TOLERANCE IN RICE (ORYZA SATIVA L.) AT EARLY SEEDLING GROWTH: GENOTYPIC VARIABILITY, IDENTIFICATION AND SELECTION

Plant growth response of four week old seedlings of 48 rice lines/cultivars to four NaCl levels (0, 10, 15 and 20 dS/m) was assessed in solution culture. Genotypic responses were compared from measures of absolute and relative salt tolerances. Increasing salinity levels in the growing medium differentially reduced fresh shoot weight, seedling fresh weight and specific shoot length. Shoot length, root length, seedling length, fresh root weight, specific root length, dry shoot weight, dry root weight and seedling dry weight were less affected differentially. The rice genotypes originating from Pindi Bhatian exhibited significantly greater salinity tolerances overall than those originating from Faisalabad, Kala Shah Kaku and IRRI. Estimated broad sense heritabilities indicated that phenotypic variance exceeded that of genotypic by nearly two orders of magnitude. These findings indicate that the genetic improvement of salt tolerance in rice through selection will be problematic due to masking effects of the environment, and imply rigorous and careful selection of salt tolerant genotypes.