Salt stress response index and tolerance mechanisms of citrus rootstocks

The response of some citrus rootstocks to irrigation water salinity was evaluated at Regional Research Station Abohar during 2018–2019 using membership function value (MFV) approach. The seedlings were irrigated with mild saline water (EC 2 dS m⁻¹) for 180 days along with canal water as control (EC 0.13 dS m⁻¹). After 60 days of first saline water treatment (DAT), average MFV was statistically comparable among rootstocks. However, at 120 and 180 DAT, MFV ranged between 0.271–0.631 and 0.252–0.709, respectively. During both the intervals, Rangpur Lime registered significantly (p<0.05) higher MFV. A positive and significant correlation between MFV and root K and Cl concentrations, photosynthesis rate, stomatal conductance, peroxidase, catalase and superoxide dismutase activities indicated the importance of these parameters in imparting salt tolerance to citrus rootstocks. In overall, the relative salt tolerance of rootstocks followed the order: Rangpur Lime > Cleopatra Mandarin > Volkamer Lemon > Rough Lemon > Carrizo.