Iron toxicity-related morphological and biochemical variations of selected rice (Oryza sativa L.) varieties in Sri Lanka

Iron (Fe) toxicity is recognized as a widely observed nutritional disorder that lowers rice crop productivity worldwide. The high concentration of Fe in soil may also alter the uptake and accumulation of other mineral elements. However, the relative change in the accumulation of other mineral elements affected by Fe toxicity is largely unknown. Therefore, this experiment studied the mineral nutrition of two Fe-tolerant (Bw372 and Bw267-3) and Fe-susceptible (Bw272-6B and Bg359) rice varieties to variable Fe concentration in the growing medium. Four Fe concentrations were used; 7 mgL− 1(1.25 × 10− 4molL− 1), 100 mgL− 1 (1.79 × 10− 3molL− 1), 300 mgL− 1 (5.37 × 10− 3 molL− 1), and 500 mgL− 1 (8.95 × 10− 3 molL− 1). The experiment was conducted as a hydroponic system with 15 plants as replicates for each treatment combination. Results revealed that, when increasing Fe concentration in the growing medium, tissue Fe, Na, and Co concentrations increased while tissue Mn, Mg, Mo, Cu, Zn, and Cd concentrations decreased for all the varieties. When comparing varieties, the concentration of Fe in Bw372 was the lowest, and that in Bw272-6B was the highest. As a result, the reduction in shoot dry weight (SDW) and root length (RL) to increased Fe concentration was the lowest in Bw372 (33% for SDW and 40% for RL) and highest in Bw272-6B (64% for SDW and 52% for RL). Moreover, Bw372 and Bw267-3 did not show bronzing symptoms when grown in any of the tested Fe concentrations. These traits have contributed to Bw272-6B being susceptible and Bw372 being tolerant to Fe toxicity.