Comparative morpho-physiological traits, antioxidant defense and nutritional profiling under Cd stress of japonica-indica elite rice ( Oryza sativa L.) cultivars

Cadmium (Cd) is a water-soluble heavy metal. It has adverse effects on rivers and underground water in developing countries. Rice is a hydrophilic crop grown by extensive utilization of water. Presence of Cd in paddy water can lead to destruction of both quality and quantity of rice. To access the variation in impact of Cd on two elite rice cultivars of Pakistan i.e., indica (Super Basmati) and japonica (JP-5), a pot experiment with three replicates was carried out in completely randomized design. To induce stress conditions, both cultivars were subjected to elevated levels of Cd (50 mg/kg) as cadmium chloride. The results indicated that Cd stress had a high impact on morpho-physiological traits such as grain yield, thousand grain weight and tiller number in Supper Basmati compared to JP-5. This was due to high accumulation of the reactive oxygen species and lower levels of enzymatic antioxidants including peroxidase, catalase, carotenoids, glutathione, ascorbate peroxidase, glutathione peroxidase, and phenols in Super basmati. The Cd translocation from roots to leaf and subsequently grains was higher in Super Basmati compared to JP-5. Nutritional profiling of grains showed low level of carbohydrates and proteins in Super Basmati compared to JP-5 which shows that JP-5 is more tolerant, nutritious, and high-yielding under Cd-stress conditions. JP-5 is thus recommended to be cultivated in Cd-stressed areas in future and breeders can further use it to improve crop performance in Cd-stress soil and ensure sustainable food production around the world.