Reproductive stage tolerance to salinity and alkalinity stresses in rice genotypes

Salinity and alkalinity (sodicity) seriously threaten rice production in south Asia. Improving screening methodologies for identifying sources of tolerance is crucial for breeding salt tolerant rices. Rice genotypes of varying tolerance (tolerant, semi-tolerant and sensitive) were screened in saline soil of electrical conductivity, ECe 4 and 8 dS/m and alkali soil of pH 9.5 and 9.8 in lysimeters. Vegetative growth events were less affected by both the stresses in comparison to reproductive stage. Grain yield was reduced by 26.7%, 45.7% and 50.3% at ECe 8 dS/m in three tolerance groups respectively. At pH 9.8 the reduction was 25.1%, 37.2% and 67.6% in the three groups respectively. Higher floret fertility contributed to higher seed set and grain yields in tolerant genotypes whereas higher spikelet sterility led to poor seed set and lower grain yields in sensitive genotypes. The 1000 grains weight was also significantly reduced at ECe 4 or pH 9.8. Screening at reproductive stage for morphological traits like floret fertility is thus more useful to identify rice genotypes tolerant to both salinity and alkalinity stress. Genotypic (G) and environmental (E) effects and GE interactions were highly significant for the growth attributes and grain yield. Based on analysis of variance, genotypes tolerant to salinity and alkalinity as well to both the stresses were identified.