Abstract Purpose To assess the response of seven citrus rootstocks, including five described-HLB tolerant varieties and two reference rootstocks (Carrizo citrange, salt-sensitive, and Cleopatra mandarin, salt-tolerant), to salinity stress. Methods A pot experiment was conducted including two factors: (i) salinity treatments (0, 25, 50, and 75 mM NaCl) and (ii) rootstock. The effects of treatments on growth, physiological parameters (chlorophyll content, stomatal conductance, relative water content), ion accumulation, and phytotoxicity symptoms in citrus rootstocks were evaluated under controlled greenhouse conditions. Results Increasing NaCl concentrations resulted in higher accumulation of Na + and Cl − in the leaves, as well as an increased leaf-to-root ratio. However, the effects of the treatments on growth, chlorophyll content, and stomatal conductance depended on the rootstock since significant interactions between factors were observed. The rootstocks US802, B11R3T27, B11R5T36, B11R5T64 and Carrizo citrange exhibited reduced stomatal conductance and showed severe symptoms of chlorosis and defoliation, which could be attributed to the increased accumulation of Na + and Cl − in the leaves. In contrast, Cleopatra mandarin and US942 showed no significant symptoms of salt toxicity. Both rootstocks effectively limited ion accumulation in the leaves compared to the others. In the case of Cleopatra mandarin, this could be attributed to salt exclusion capacity and reduced ion uptake, meanwhile US942 accumulated ions in the roots and prevented their transport to the leaves. Conclusions Salinity tolerance in studied rootstocks appears to be associated with different mechanisms, such as salt exclusion and reduced ion transport, which were able to avoid phytotoxic effects.
Moreno-Lora et al. (Tue,) studied this question.
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