Effect of salinity stress on some physiological traits of selected citrus seedlings and identification of tolerant genotypes

In order to identify salinity tolerant genotypes, seedlings of tolerant and susceptible genotypes named ‘Cleopatra’ mandarin and ‘Troyer’ citrange, and some screened citrus genotypes to salinity (sum of 28 genotypes) from Citrus Research Institutes of Ramsar and Darab were assessed. Three levels of sodium chloride including 0, 40 and 90 mM were applied on eight months seedlings for 12 weeks under greenhouse conditions in a factorial experiment based on completely randomized design with three replications. Physiological traits including chlorophylls a and b, proline, lipid peroxidation, enzyme activity of superoxide dismutase, ascorbate peroxidase and catalase, total protein and quantum yield of photosystem Π were studied. The results of physiological traits showed that salinity reduced the chlorophyll a and b, total protein, quantum yield of photosystem II, ascorbate peroxidase activity and catalase activity in studied genotypes. In this study, proline content, malondialdehyde concentration and superoxide dismutase activity increased under salt stress. Genotypes G8, G44 (sour orange), G19, G25 and G42 (bergamot) in several traits including chlorophyll content, lipid peroxidation, proline content and enzymes activity were better than others. G8 genotype was better than salinity tolerant cultivar, ‘Cleopatra’, in some traits. Consequently, mentioned genotypes could be considered as tolerant or semi- tolerant genotypes for further research or practical purposes.