Evaluation of the responses of contrasting sensitive and tolerant rice genotypes to arsenic stress

The threats of arsenic (As) contamination of rice grains and rice-based food products are being experienced globally. Arsenic toxicity to rice (Oryza sativa L.) affects its production and grain quality. In this work, screening of 67 rice genotypes was performed against As stress (25 mu M and 50 mu M, in the form of arsenite [As(III)]) for 7d in lab conditions on the basis of germination and early growth of seedlings. Germination percentage, root and shoot length, and seedling vigour were analyzed. The genotypes showed a wide range of variation in germination percentage, and seedling growth in response to both control and As(III) stress. The comparative evaluation of genotypes could demarcate them into sensitive (e.g. Shobhini and DRR Dhan-41) and tolerant (e.g. Pooja and Vivek Dhan) categories. To further investigate the behavior of contrasting varieties, a tolerant (Pooja) and moderately sensitive (CO-50) variety of rice were subjected to As stress for variable concentrations (0-25 mu M; fixed duration 5 d) and duration (1-15 d; fixed concentration 25 mu M). The accumulation of As by tolerant and sensitive varieties in roots, old leaves and young leaves was found to be significantly lower in Pooja than in CO-50. The differential As accumulation reflected in growth and biochemical responses (malondialdehyde level, superoxide dismutase activity and total non-protein thiols). The results demonstrate the potential of using contrasting rice varieties for future breeding or gene editing approaches to develop low arsenic accumulating rice cultivars.