Rainfed Rice Genotypes Adaptability to Excess Iron Stress in Hydroponic Culture

Iron (Fe) toxicity is a nutritional disorder that affects lowland rice (Oryza sativa L.). Excessive amounts of reduced Fe(II) in the soil solution, its uptake by the rice roots, and its transpiration-driven transport result in elevated Fe(II) concentrations in leaf cells that catalyze the formation of reactive oxygen species. The oxidative stress causes rusty brown spots on leaves (bronzing) and the reduction of biomass and yield. While the use of resistant genotypes is the most promising approach to address the problem, the stress appears to differentially affect rice plants as a function of plant age, climatic conditions, stress intensity and duration, and the dominant adaptation mechanism. We comparatively assessed ten contrasting 4-week-old rice genotypes regarding their response (symptom score, agronomic traits, Fe concentrations in different plant parts) to different iron stress intensities (0, 500, 1000 and 1500 mgL-1 Fe(II)) exposed for three days in an experiment conducted during the year 2021 at Assam Agricultural University, Jorhat. Rice varieties Bahadur and Podumoni were found to tolerate high iron concentrations through an exclusion mechanism.In contrast, Joymoti, Ranjit and Mahsuri could tolerate excess iron concentration even after imbibing iron into the plant system. Moniram and Bahadur could also tolerate high iron conditions by maintaining moderately high leaf iron concentrations. Kushal and Podumoni were sensitive and extremely sensitive, respectively.