Standardization and Comparative Evaluation of Salinity Stress Levels for Rice Seed Germination Using the Paper Towel Method Under Laboratory Conditions

Abstract

Salinity stress poses a serious constraint to rice production by impairing seed germination and early seedling growth. The present study was undertaken to evaluate the salinity tolerance of rice (Oryza sativa L.) genotypes under laboratory and hydroponic conditions, with particular emphasis on seed quality traits. The experiment was conducted at the Department of Seed Science and Technology, College of Agriculture, University of Agricultural Sciences, Raichur. Thirty rice genotypes were subjected to five salinity treatments comprising 0 (control), 40, 60, 80 and 100 mM NaCl, arranged in a factorial completely randomized design with four replications. Germination and seedling performance were assessed using the paper towel method in accordance with ISTA guidelines. Increasing salinity levels resulted in a significant decline in seed germination percentage, root and shoot length, seedling dry weight, and seedling vigour indices, while the proportion of abnormal seedlings increased. The control treatment recorded the highest germination (90.92%) and seedling vigour, whereas exposure to 100 mM NaCl reduced germination to 82.15%, indicating an overall reduction of approximately 9%. Considerable genotypic variation was observed in response to salinity stress. Genotypes NVSR 6494, NVSR 6489, CSR 23, CSR 104-10-2 and RP 6688-16-397 exhibited better performance by maintaining higher germination and vigour under saline conditions, whereas GNV 10-89, BPT 5204 and RP 6684-CGR 13 showed pronounced sensitivity. The findings demonstrate substantial variability among rice genotypes at the germination stage and identify promising lines for utilization in salinity tolerance breeding programmes.