S. Shirahmadi - Department of Horticultural Sciences, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Islamic Republic of Iran.
M. Esna-Ashari - Department of Horticultural Sciences, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Islamic Republic of Iran.
S. Aliniaeifard - Department of Horticulture, Aburaihan Campus, University of Tehran, Tehran, Islamic Republic of Iran.
Gh. Abbas Akbari - Department of Agronomy and Plant Breeding Sciences, Aburaihan Campus, University of Tehran, Tehran, Islamic Republic of Iran.

To study salinity tolerance of ۱۵ basil accessions widely distributed across Iran, they were grown under two salt levels including control (no NaCl) and ۴۰ mM NaCl (Hoagland nutrient solutions with EC of ۱.۱ and ۵.۵ dS m-۱, 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 ۴۳% 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 ۱۹ to ۴۵% 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.

Chlorophyll a fluorescence, Cluster analysis, Growth parameters, Ocimum spp., Salinity stress.