Rice yield gap due to iron toxicity in West Africa

Iron toxicity is a widespread nutrient disorder of lowland rice in West Africa. Soluble iron present in the soil solution under waterlogged conditions is absorbed by roots and accumulates in leaves. It causes poor growth and tillering and severe yield reductions associated with leaf discoloration. Field experiments were carried out from 1994 to 1998 on two iron-toxic sites and one non-toxic site in West Africa to estimate the effect of iron toxicity on rice cropping and to evaluate the tolerance of promising rice cultivars available in West Africa. To have a good estimation of the iron toxicity yield losses, the yield potential was calculated in iron-toxic sites from the Oryza-S model, a rice growth and yield model. With simulation, iron toxicity could be reported to reduce yield (yield gap) by from 10 to 100% with an average of 45%. Yield loss depended on rice cultivars, iron toxicity intensity and crop management (water control and fertilization). The large rice genetic variability in response to iron toxicity and the correlation between leaf-symptom score and grain yield across genotype could be a breeding advantage for rapidly producing improved rice cultivars for iron-toxic conditions. (Résumé d'auteur