Selecting salt-tolerant citrus rootstocks

Abstract

The salt-tolerance of 28 imported rootstocks was compared with three citrus rootstocks used widely in South Australia. The experiment was conducted in a shadehouse, using highly saline irrigation water (8700 8S/cm conductivity) applied to vigorous, chloride-excluding genotypes.Fifteen of the imported rootstocks showed no significant growth reductions after 84 days of salt treatment and were therefore considered as being highly salt tolerant. All fifteen outperformed the three locally used rootstocks (Paramatta sweet orange, Cleopatra mandarin and Troyer citrange), which experienced significant growth reductions during salt treatment. Seventeen rootstocks showed no significant difference from each other in leaf chloride (Cl-) concentrations on day 84 and were therefore identified as the best Cl- excluders. Ten rootstocks had the combined attributes of salt tolerance on the basis of growth response, Cl- exclusion ability and absence of phytotoxic leaf symptoms. The relationship between growth response of plants during salt treatment and Cl- -accumulation in leaves was not significant.The three locally used rootstocks were not significantly different (P < 0.05) in their growth response to high salinity, but differed from each other in their Cl exclusion ability.Investigation of nutrient interrelationships showed that chloride uptake was negatively correlated with nitrogen (N) uptake and positively correlated with calcium (Ca) and sodium (Na) uptake. Sodium uptake was negatively correlated with N, potassium (K) and manganese (Mn) uptake.