Molecular and Physiological Analysis of Aluminum Tolerance in Maize Recombinant Inbreds

Aluminum (Al) toxicity is a major constraint for crop production on acid, Al toxic soils, that occupy over 50% of the potentially arable lands in the world. Aluminum is ubiquitous in soils and when solubilized at pH values below 5.0, becomes highly phytotoxic as Al3+, causing severe yield reduction to sensitive crops. Al tolerance in species such as wheat, barley and sorghum appears to rely largely on a small number of genes within each species. However, quantitative inheritance for Al tolerance appears to be the general pattern observed in rice and maize. In maize, citrate exudation has been suggested as an important tolerance mechanism. However, lack of correlation between citrate exudation and differential Al tolerance observed in some maize lines suggests that other Al tolerance mechanisms may take place in maize. In this study, we undertook a physiological study of Al tolerance mechanisms focusing on citrate exudation in selected maize recombinant inbred lines for which a QTL map had been previously developed. Our results are being assessed in light of the genetic constitution of these RILs for the major Al tolerance QTLs segregating in the population. Our results support the role of citrate exudation as a major Al tolerance mechanism in maize but suggest that other mechanisms probably take place in this population