Evaluation of the salinity tolerance of Iranian citrus rootstocks using morph-physiological and molecular methods

Abstract Salt tolerant citrus rootstocks are extremely important in the area with brackish water and soil. To identify salt tolerant accessions, two well-recognized tolerant and susceptible cultivars, Cleopatra mandarin and Troyer citrange, and 42 genetically diverse citrus accessions from Iran, were evaluated under three levels of sodium chloride (NaCl) including 0, 40 and 90 mM. Five genotypes named G25, G8, G34 (Cleopatra), G42 (Bergamot) and G44 (Sour orange) were the most salinity tolerant based on stress tolerance score. Salinity tolerance was highly correlated with chlorophyll fluorescence (r = 0.55**), Na+ concentration (r=-0.51**), ascorbate peroxidase (r = 0.56**) and leaf necrosis and loss (r=-0.64**). Iranian rootstocks, G8 and G44, were more tolerant than Cleopatra. These results showed that Iran is an appropriate gene pool for salinity tolerance in citrus. The findings of relative gene expression indicated that G44 had salinity tolerance alleles for SLAH, ABCT2 and ABCT3. Considering genotypic and phenotypic results, G44 was recognized as the most salinity tolerant rootstock.