Modulation of the antioxidant system and primary metabolism confers aluminum stress tolerance in soybean

Aluminum (Al) toxicity causes a substantial crop productivity loss in acid soil. Here, we evaluated the antioxidant responses and metabolic adjustments in soybean roots after Al exposure and demonstrated that different genotypes from the same species can present distinctive strategies to avoid Al toxicity. Soybean genotypes were exposed to nutrient Clark solution (pH 4.0) under two cultivation conditions: 0 µM (control) and 100 µM AlCl 3 for 24, 48, and 72 h. Our results demonstrated that the soybean genotypes ‘P98Y70’ and ‘Conquista’ present different tolerance to Al. The root growth of P98Y70 genotype was impaired under Al treatment. Besides, this genotype showed a delay and lower activities in their antioxidant enzymes, which culminates in a high accumulation of reactive oxygen species (ROS). On the other hand, the Conquista genotype showed an early antioxidant enzymatic response through the increase in the superoxide dismutase (SOD), catalase (CAT), and total peroxidase (POX) activities at 24 h of Al exposure, whereas P98Y70 showed high SOD and POX activities only at 72 h. Besides, the Conquista genotype presented high levels of ascorbate, fructose-6-phosphate (F6P), and high activity in the glutathione peroxidase (GPX), which culminated in a low accumulation of ROS and less oxidative stress. Therefore, these traits can be used as biomarkers of Al tolerance in soybean plants when associated with an early response against Al.