Comparison of the Morpho-Physiological and Molecular Responses to Salinity and Alkalinity Stresses in Rice

Abstract

Rice is a major food crop that has a critical role in ensuring food security for the global population. However, major abiotic stresses such as salinity and alkalinity pose a major threat to rice farming worldwide. Compared with salinity stress, there is limited progress in elucidating the molecular mechanisms associated with alkalinity tolerance in rice. Since both stresses coexist in coastal and arid regions, unraveling of the underlying molecular mechanisms will help the breeding of high-yielding stress-tolerant rice varieties for these areas. This study examined the morpho-physiological and molecular response of four rice genotypes to both salinity and alkalinity stresses. Geumgangbyeo was highly tolerant and Mermentau was the least tolerant to both stresses, while Pokkali and Bengal were tolerant to only salinity and alkalinity stress, respectively. A set of salinity and alkalinity stress-responsive genes showed differential expression in the above rice genotypes under both stress conditions. The expression patterns were consistent with the observed morphological responses in these rice genotypes, suggesting the potential role of these genes in regulating tolerance to these abiotic stresses. Overall, this study suggested that divergence in response to alkalinity and salinity stresses among rice genotypes could be due to different molecular mechanisms conferring tolerance to each stress. In addition to providing a basis for further investigations into differentiating the molecular bases underlying tolerance, this study also emphasizes the possibilities of developing climate-resilient rice varieties using donors that are tolerant to both abiotic stresses.

Antioxidant Defense and Ionic Homeostasis Govern Stage-Specific Response of Salinity Stress in Contrasting Rice Varieties

“…In the present experiment, Fe +3 and Mn +2 content increased significantly in adult plant salinity and remained unaffected during combined-stages in root and shoot tissues of CSR36; however, the translocation of Fe +3 in the shoots was relatively low as compared with Mn +2 which suggests ion selectivity under salt stress in tolerant plants ( Table 2 , Figure 3 A,B). High salinity caused by saline and alkaline stress reduces the solubility of Fe +3 in solution, leading to chlorosis which was visible in Jaya under salt stress ( Figure S3B ) [ 43 ]. Compared to Fe +3 and Mn +2 , Zn +2 uptake was significantly reduced in Jaya root and shoot tissues at critical stages i.e., F-stage in stage specific and S+T+F- and S+T+F+SS-stage in combined-stage salinity stress but CSR36 exhibited significantly higher Zn +2 uptake and better translocation at these stages in shoots as compared with Jaya, indicating ion selectivity ( Table 2 , Figure S3A,B ).…”