Exploring the growth and biochemical response of canola varieties to cadmium and lead contamination

Heavy metal (HM) contamination of agricultural soils by cadmium (Cd2+) and lead (Pb2+) pose a serious risk to the crop productivity and food security. However, a workable solution is required to reduce the impact of HM contamination in soils and improve productivity. Therefore, the current study aimed to investigate the tolerance of different canola varieties against the contamination of Cd2+ and Pb2+ under field conditions. The experimental site was previously contaminated with Cd2+ (6ppm) and Pb2+ (600ppm) where canola varieties were cultivated under the randomized complete bock design (RCBD) with three replicates of each treatment. The current study evaluated the growth, biomass accumulation, chlorophyll content and biochemical attributes of canola varieties. The results of this study revealed significant variability among varieties in response to the metal stress. Under Cd2+ contaminated conditions Oscar attained highest plant height (71.42 cm), root length (33.62 cm), shoot length (34.25 cm) however under Pb2+ contaminated soil Super Raya showed maximum plant height (39.43 cm), root length (13.45 cm) and shoot length (26.34). In contrast varieties like rainbow and Sandal Canola showed inhibited growth with a significant reduction in the root, shoot length and decline in the antioxidant enzyme activity. In addition, highest superoxide dismutase (SOD) 6.63 U/g Protein, catalase (CAT) 2.87 U/g Protein, peroxidase (POD) 43.26 U/g Protein, Malondialdehyde (MDA) 76.10 nmol /g FW, Ascorbate Peroxidase (APX) 74.20 U/g Protein, Ascorbic Acid (ASA) 70.52 µg/g FW and Glutathione (GSH) 73.71 µmol/g FW activity by Oscar under Cd2+ contaminated soil. In Pb2+ contaminated soil CONII represent its potential by showing highest SOD (5.78 U/g Protein), CAT (2.81 U/g Protein), POD (52.57 U/g Protein), MDA (72.77 nmol /g FW), APX (68.24 U/g Protein), ASA (74.49 µg/g FW) and GSH (72.76 µmol/g FW) activity. In conclusion, canola varieties exhibit differential tolerance to Cd²⁺ and Pb²⁺ contamination under field conditions, with certain varieties i.e., Oscar and Super Raya demonstrating superior growth and enhanced antioxidant defense mechanisms, making them suitable candidates for cultivation in heavy metal–contaminated soils.