Abstract Salinity tolerance levels and physiological changes were evaluated for twelve rice cultivars,
including four white rice and eight black glutinous rice cultivars, during their seedling stage
in response to salinity stress at 100 mM NaCl. All the rice cultivars evaluated showed an apparent
decrease in growth characteristics and chlorophyll accumulation under salinity stress. By contrast
an increase in proline, hydrogen peroxide, peroxidase (POX) activity and anthocyanins were
observed for all cultivars. The K+/Na+ ratios evaluated for all rice cultivars were noted to be
highly correlated with the salinity scores thus indicating that the K+/Na+ ratio serves as a reliable
indicator of salt stress tolerance in rice. Principal component analysis (PCA) based on physiological
salt tolerance indexes could clearly distinguish rice cultivars into 4 salt tolerance clusters.
Noteworthy, in comparison to the salt-sensitive ones, rice cultivars that possessed higher degrees
of salt tolerance displayed more enhanced activity of catalase (CAT), a smaller increase in anthocyanin,
hydrogen peroxide and proline content but a smaller drop in the K+/Na+ ratio and chlorophyll
accumulation.