Genetic variable exists among wheats for tolerancce to aluminum (Al) toxicity. Although retarded root growth in susceptible wheat varieties is the most characteristic symptom of Al toxicity, beware that this symptom can be confused with nematode infestations and root diseases.

1. Symptoms: High concentrations of aluminum will first reduce development of the roots, giving them a stubby appearance. They will often have a brownish color. Typical symptoms in the above ground portion of the plant are small leaves, and shortened and thickened internodes.

   The first specific foliar symptom of Al toxicity (as with boron and phosphorus) is a yellowing along the margin near the tip of the oldest leaf. Within a few days brown lesions form in these chlorotic regions and work in from the margins resulting in the formation of indentations. The progress of these toxicity symptoms is rapid. Old leaves become drought stressed and withered and at times collapse in the center.

2. Development: This toxicity is associated with low soil pH, and it can be reduced by liming.
3. Hosts/Distribution: Though many minerals can be toxic to plants, the most common toxicity affecting wheat is caused by an excess of free aluminum. Genetic variability exists for aluminum tolerance within bread wheats and triticales.
4. Importance: Large areas of potentially productive land with acid soils (low pH) have toxic levels of free aluminum.