Assessing Aluminum Stress Resilience in Common Bean Roots: Phenotypic, Histochemical, and PvGST/PvPOD Gene Expression Analysis

Abstract

Common bean (Phaseolus vulgaris L.) is grown in various parts of the world. Aluminum (Al) toxicity poses a significant and widespread challenge in marginal areas with unfavorable soil qualities where common bean is grown. In acidic soils, stable forms of Al dissolve into the soil solution and inhibit root growth and function by injuring the root apex with phytotoxic ions. This leads to the development of a smaller root system, adversely affecting crop yield. In this study, the phenotypic evaluation for relative root elongation of 10 common bean genotypes/cultivars under Al stress (50 µM), the impact of Al toxicity using different histochemical dyes (Evan’s blue and Schiff’s reagent) and the expression levels of PvGST (Glutathione S-transferases) and PvPOD (peroxidase) genes in the root tissues of the most resistant/sensitive common beans under Al stress (50 µM) and control conditions (0 µM) were investigated. The maximum relative root elongation value (71.9%) was found in Önceler-98 cultivar, while the lowest value (14.1%) was obtained from Blksr-19 genotype. Histochemical applications used in the study supported phenotypic results. The cracks at the root tip and high blue color intensity were detected in Schiff’s reagent and Evan’s blue dyes in the Blksr-19, respectively. The expression levels of PvGST and PvPOD genes in the root tissue of the Blksr-19 (Al-sensitive) were highly upregulated at 24 h of Al stress treatment. The results revealed that these genes might be involved in the common bean root tissue's defense mechanism against Al stress for the first time. The findings herein will help plant breeders develop common bean cultivars tolerant to Al toxicity.