Exogenous Magnesium Application as a Salinity Mitigator in Cashew Genotypes

Cashew (Anacardium occidentale 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.