Determination of Salinity Tolerance in Pigmented Rice Genotypes at Seedling Stage

Rice is the principal cash crop of Pakistan, however, its yield is severely affected by salinity. In arid and coastal areas of rice cultivation, salinity is one of the major factors that affect its yield. In present study genetic variability and correlation analysis between different morpho-physiological traits at the seedling stage of various rice genotypes were studied. The experiment was design in a completely Random Design with three replications. At the seedling stage, rice seedlings were treated with two sodium chloride concentrations and various morphological and physiological parameters were investigated. For all of the traits analysis of variance revealed significant differences among the genotypes. Correlation analysis showed that under normal conditions, most of the studied traits had significant positive correlations with each other except root dry weight and relative water contents. While in T₁, most traits had significant positive correlation with each other, however in T₂, correlation of some of the traits was significantly positive while few traits showed significantly negative correlations with each other. From the results, it was found that seedlings treated with 50 and 200 mM salt solutions were smaller than the control; however, secondary leaves developed in them. Seedlings treated with 50 and 200 mM salt solutions could not progress toward secondary leaves. Under salt stress, lower fresh weight of seedlings was found then normal seedlings. With salt treatments, the chlorophyll contents of seedlings decreased significantly. Out of nine principal components (PCs), the first two PCs showed significant genetic variation under normal and salinity conditions. The first two PCs under normal, T₁ and T₂showed 81%, 84% and 71% total variation respectively in the studied genotypes. From the analysis, it was found that traits such as root length, root fresh and dry weight, chlorophyll contents and stomatal conductance at the seedling stage would be useful criteria for genetic improvement. As compared to white rice, pigmented rice, results suggested that studied pigmented genotypes could be beneficial for further study of salinity effects on growth processes, morpho-physiological concerns and advanced stages of growth, since the salinity tolerance of a crop at germination and early seedling stage may not parallel to advanced stage. Future pigmented rice breeding programs may benefit from outperforming genotypes under salt stress conditions and early selection for the features suggested in this work may prove to be successful in creating high-yielding and salinity-tolerant rice varieties.