Exogenous Magnesium Application as a Salinity Mitigator in Cashew Genotypes

Cashew (<i>Anacardium occidentale</i> L.), native to northeastern Brazil, holds significant socioeconomic value, but its cultivation is limited by salinity, which is common in semiarid regions. This study evaluates foliar magnesium (Mg) application as a strategy to mitigate salinity stress in cashew seedlings. A greenhouse experiment was conducted with two genotypes (CCP 76 and AT01), two irrigation salinity levels (0.5 and 2.5 dS m^-1), and three Mg doses (0, 1, and 2 mL L^-1). Salinity reduced growth, physiological parameters, and stomatal conductance. Foliar Mg application, particularly at 1 mL L^-1, alleviated these effects by increasing root dry mass, stomatal conductance, internal CO₂ concentration, and intrinsic water-use efficiency, especially in genotype AT01. The 2 mL L^-1 dose showed inconsistent responses, suggesting toxicity. Overall, Mg application mitigates salinity effects in cashew, with efficiency dependent on genotype and dose, and AT01 demonstrating greater tolerance.