The Response of Three Mandarin Cultivars Grafted on Sour Orange Rootstock to Salinity Stress

ABSTRACT Citrus growth is often constrained by salinity, but citrus rootstocks respond to salinity differently. A greenhouse study was carried out in a completely randomized design with three cultivars of mandarin (‘Younesi,’ ‘Clementine,’ and ‘Yashar’) and four levels of salinity (control, 1, 3, and 5 dS/m) in three replications to explore the mechanism by which salinity stress affects photosynthetic and growth factors of mandarin cultivars. After applying salinity treatments, shoot fresh and dry weight, root fresh and dry weight, branch number, leaf number, plant height, leaf and root potassium (K), sodium (Na), and calcium (Ca) contents, chlorophyll content, proline content, leaf nitrogen, and protein content, electrolyte leakage, and sugar content were measured. The results showed that salinity stress reduced vegetative and photosynthetic factors in all three cultivars. Root and leaf K and Na contents, chlorophyll a, total chlorophyll, proline content, electrolyte leakage, and sugar and protein contents were affected by cultivars. Salinity affected root and leaf K and Na contents, chlorophyll a and b and total chlorophyll contents, proline, and electrolyte leakage significantly. The interaction of cultivar and salinity was also significant on chlorophyll a and total chlorophyll contents, leaf N and protein contents, and electrolyte leakage. Salinity stress reduced vegetative and photosynthesis factors of all three cultivars.