TOLERANCE OF RICE CULTIVARS TO IRON TOXICITY

Iron toxicity is an important growth-limiting factor for flooded rice [Oryza sativa L.] production in various parts of the world, including Brazil. Data related to the reaction of rice cultivars to iron concentrations are limited, especially for large numbers of cultivars. Forty rice cultivars were grown in a greenhouse in nutrient solutions containing 0.09, 0.89, and 1.78 mM Fe (5, 50 and 100 ppm Fe). The effects of excess iron were measured on plant height, root length, and root and shoot dry weight. Root and shoot dry weight were found to be more sensitive to excess iron concentration. Based on dry matter yield, reduction of shoots at higher Fe concentrations compared to the optimum or control treatment, rice cultivars were classified as tolerant, moderately tolerant, moderately susceptible. The effect of Fe concentrations on concentrations and contents of other nutrients was also investigated. Higher concentration of Fe in the nutrient solution exerted an inhibiting effect on the concentrations and contents of almost all macro and micronutrients.