To study salinity tolerance of 15 basil accessions widely distributed across Iran, they were grown under two salt levels including control (no NaCl) and 40 mM NaCl (Hoagland nutrient solutions with EC of 1.1 and 5.5 dS m-1, respectively). The studied parameters included morphological characteristics and chlorophyll a fluorescence transient (OJIP) measurements. According to the results, the accessions were categorized into three clusters under the salt stress. Salinity had significant effects on morphological and growth parameters in all basil plants. Compared to the control, NaCl decreased plant height. The number of leaves in Khash, Zabol, and Orumiyeh accessions was more than the others. Both salt and accession caused a decrease up to 43% in leaf fresh weight, emphasizing the major role of accession when salinity was applied. Salinity influenced negatively the biomass yield in basil plants. These decreases varied from 19 to 45% depending on the accessions. Salt treatment of basil plants decreased photosystem II activity, as evaluated from chlorophyll fluorescence data. The parameters that were most affected by salt treatment were maximal quantum yield of PSII photochemistry (FV/FM) and calculated Performance Index (PIABS). Overall, among the studied basil accessions, genotype Ardabil had superior tolerance to salt stress. Furthermore, the most of accessions can be used for studying the mechanism of salinity tolerance in basil plant.
