Iron Toxicity

Lowland rice production in tropical regions is widely affected by iron toxicity. This is a condition caused by the microbial reduction of insoluble Fe(III) into soluble Fe(II) and involves an excessive uptake of Fe (II) by the rice roots and its acropetal translocation via xylem flow into the leaves. There, Fe(II) can cause oxidative stress via an elevated production of oxygen radicals, leading to yield losses of up to 80%. The severity of the stress and the associated yield loss depend mainly on the amount of Fe (II) and the time of its occurrence and on type and extend of rice cultivar’s tolerance mechanisms. The effectiveness of diverse adaptation mechanisms to tolerate iron-toxic conditions and its variation in the available germplasm is largely unknown. To date, no systematic attempt has been made to use adaptation mechanisms as a tool in rice breeding programs for iron toxicity tolerance or to differentiate the effectiveness of adaptation strategies by the prevailing type of Fe (II) toxicity. We hypothesize that the environment-specific spatio-temporal variation in conditions of iron toxicity occurrence requires differential expression of adaptation mechanisms and their matching with prevailing iron stress situations. The type and the efficiency of adaptation mechanisms will be evaluated in representative lowland rice cultivars grown in hydroponics for the

1) Identification of tolerant cultivars;

2) Evaluation of adaptation strategies;

3) Classification of adaptation strategies regarding their effectiveness to control/tolerate different Fe stress types.