Differential Chromium (Cr) Accumulation and Tolerance in Brassica juncea Cultivars for Phytoremediation in Turkey

Abstract Several agricultural areas in the Anatolian Plateau of Turkey are contaminated with chromium due to mining and leather tanning activities, posing a serious threat to both safe farming and human health. Cleaning polluted soils for reuse in agriculture is a vital and primary goal of this research. This study aimed to identify suitable Brassica juncea (L.) Czern. cultivars for phytoremediation of metal-contaminated soils in Turkey, with the goal of promoting safe farming practices. Six cultivars: ‘Early raya’, ‘Sindh raya’ ‘S-9’, ‘Ganj sarhen’, ‘Mehran raya’ (‘JS-13’), and ‘THB-81’, developed by the Agricultural Institute of Pakistan for drought and salt tolerance, were tested for metal tolerance at different chromium (Cr) levels (0–1000 μM). Physiological parameters were recorded, and the contents of chromium (Cr), calcium (Ca), iron (Fe), magnesium (Mg), and potassium (K) in plant tissues were quantified using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Additionally, the gene expression of several enzymes induced by ROS was examined using RT-qPCR. ‘Early raya’ and ‘Sindh raya’ under Cr stress showed different expression patterns of these genes, highlighting significant genotypic differences in chromium uptake, nutrient balance, and molecular responses. Our results classified the cultivars into three groups: ‘Early raya’ and ‘THB-81’ as accumulators; ‘Sindh raya’ and ‘S-9’ as excluders; and ‘Ganj sarhen’ and ‘JS-13’ as intermediate Cr accumulators. This study contributes to the understanding of genotype-specific detoxification strategies in Brassica juncea. These findings may assist future studies on breeding and phytoremediation and will help develop approaches for managing Cr-contaminated soils in Turkey and other countries with similar environmental problems.