Pre-Harvest MeJA Application Counteracts the Deleterious Impact of Al and Mn Toxicity in Highbush Blueberry Grown in Acid Soils.

Volcanic ash-derived soils are characterized by low pH (pH ≤ 5.5) with increased concentrations of aluminum (Al) and manganese (Mn), which decreases plant growth, fruit quality, and yield. Methyl jasmonate (MeJA) improves abiotic stress tolerance. Our work aimed to evaluate the application of MeJA's impact on the growth, antioxidant defense, and fruit quality of highbush blueberry grown under Al and Mn toxicity. A field assay was conducted with four-year-old bushes of highbush blueberry cultivar Legacy under eight treatments (Control, Al (87% of Al saturation), Mn (240 mg kg), and Al-Mn with and without MeJA application). Physiological, biochemical, and fruit quality parameters were measured. Growth rate significantly decreased with Al (20%), Mn (45%), and Al-Mn (40%). MeJA application recovered the growth rate. Photosynthetic parameters were not affected. Antioxidant activity increased under all treatments compared with controls, being higher with MeJA application. Total phenols (TP) were decreased in plants under Al (43%) and Mn (20%) compared with controls. MeJA application increased TP in all treatments. Fruits of bushes under Al and Mn toxicity with MeJA applications exhibited an increase in fruit firmness and weight, maintaining suitable contents of soluble solids. Our results provide insights about the beneficial effect of MeJA application on growth, antioxidant properties, and fruit quality of highbush blueberry plants grown in acid soils under Al and Mn toxicity.