In vitro study of chitosan on growth improvement of citrus rootstocks under sodium chloride stress

Salinity is an abiotic stress that reduces the growth and yield of plants. Citrus is categorized as a salt sensitive tree. Hence, a study was conducted to investigate the effect of chitosan on biochemical and nutritional features of two important citrus rootstocks in different sodium chloride levels under in vitro condition. The experiment was conducted as a factorial in a completely randomized design with three replications. The first factor was sodium chloride concentration at four levels (0, 50, 75 and 100 mM), the second factor was chitosan at three levels (0,50 and 100 ppm) and the third factor was rootstocks (citrange and sour orange). Murashige and Skoog media were used. The treatments were added to the medium during the first culture. According to the results, salinity, chitosan and citrus rootstocks interaction in the most tested parameters were significant. With increasing in salinity, the leaf number, shoot length and potassium and calcium content of sour orange and citrange leaf decreased significantly, while proline content, soluble sugar, leaf chloride and super oxide dismutase activity had shown increased significantly. Chitosan, as a growth promoter, was increased the number of leaf and shoot length compared to control treatment (chitosan-free) under stress. Due to the low absorption of chlorine ion, maintaining more potassium ion and the greater accumulation of proline and soluble sugars, in response to salt stress, sour orange had shown more tolerant than citrange. Finally, chitosan could be proposed as a combination to reduce the adverse effects of salinity stress by stimulating antioxidant enzymes and neutralizing reactive oxygen species.