Screening of ‘King’ mandarin (Citrus nobilis Lour) × Poncirus trifoliata ((L.) Raf.) hybrids as salt stress-tolerant citrus rootstocks

This work evaluates new citrus hybrid tolerance to salt stress compared to Carrizo citrange. Growth parameters, ion concentration, photosynthetic parameters, leaf water relation, plant damage and proline concentration were assessed in plants irrigated with 0 (control) or 60 mM of NaCl for 60 days. Some hybrids presented marked salt-stress symptomatology like sharp decreases in plant biomass and RGR parameter, and high leaf burn and abscission percentages. While Cl− accumulation in most salinised genotypes was recorded in all the plant fractions, accumulation occurred in some hybrids only in their aerial organs. Stomatal conductance also lowered under salt conditions in all the hybrids, whereas the internal CO2 concentration (Ci) tended to increase. Salt stress lowered the leaf water potentials in all the 0501 hybrids. As a response, the salinised plants induced proline accumulation. The main trait that improved salt tolerance in some genotypes is apparently linked with the imbalance among Cl−, Na+ and K+ ions, especially enhanced K+ uptake and transport rates which delay plant damage.