Aluminium sensitivity and tolerance in model and elite wheat varieties

Three wheat varieties of Atlas66 (Al-tolerant genotype), EM12 (a major elite cultivar in China) and Scout:66 (At-sensitive genotype) were used to investigate their potential mechanisms of Al toxicity. Al concentrations of 50, 75, 100 mu mol l(-1) were used and the inhibition on root elongation between Scout66 and EM12 is significantly higher than that of Al-tolerant Atlas66, which is negative correlated to the At absorption in root apices. Organic acids secretion was checked 24 h after At stress and only malate was detected in Atlas66, but none of the organic acids were detected in the others, suggesting that secretion of malate in root is a major mechanism of At resistance in Al-tolerant wheat genotype. The root cell ultrastructure showed less damage in Atlas66 than that in Scout66 and EM 12 under At stress by transmission electron microscopy (TEM) technique. Tissue culture was carried out and the callus induction frequencies were all decreased on the media containing At. The decrease of callus induction frequencies was less in Atlas66 than that in the others. It is concluded that At damages the cell ultrastructure, resulting in the inhibition of acids secretion and cell division, which implies that the damage of cell ultrastructure is probably the key factor in Al inhibition of root growth.