Soil salinity is a major environmental constraint affecting avocado (Persea americana Mill.) productivity. In this study, we evaluate the physio-morphological and molecular responses of two avocado varieties, drymifolia (sensitive) and americana (tolerant), subjected to increasing NaCl concentrations for 60 days. Our results reveal distinct adaptive strategies. While salinity reduced total biomass in both genotypes, var. americana exhibited superior resilience, characterized by preferential biomass allocation to the root system. Ion analysis demonstrated that tolerance was not mediated by K+ homeostasis, but rather by the differential management of toxic ions. var. americana effectively sequestered chloride Cl− in the roots, whereas var. drymifolia exhibited a breakdown of the exclusion mechanism at 60 mM NaCl, with shoot Cl− concentrations exceeding those of the root, leading to severe toxicity. At the molecular level, qPCR analysis of the Na+ transporters PaHKT1 and PaSOS1 showed no expression pattern correlated with salt stress. Bioinformatic assessment revealed significant structural divergences and a lack of conserved functional domains in these proteins. These findings challenge the applicability of the classical sodium-exclusion model (typical of Liliopsida and Magnoliopsida) to avocado. We conclude that salt tolerance in this Lauraceae species is primarily driven by root-mediated Cl− exclusion rather than canonical Na+ transport pathways.
Suárez-Rodríguez et al. (Tue,) studied this question.