An experiment was conducted to study the aluminum tolerance of the wheat cultivars BH-1146, IAC-17 and Siete Cerros in nutrient solutions containing 10 mg/l of Al3+ combined with three salt concentrations (0.1, 0.2 and 0.5-strength nutrient solutions) and five levels of Mg (0, 9.6, 48.0, 96.0 and 192.0 mg/l). The pH was initially adjusted to 4.0 and maintained about that value throughout the experiment. The tolerance was evaluated by measuring the root growth in an aluminum-free complete full-strength nutrient solution after a previous treatment for 24, 48 and 72 hours in treatment solutions. The cultivar BH-1146 showed tolerance and IAC-1 7, moderate tolerance to Al3+, regardless the Al-ionic activity, Mg concentration and the ionic strength of the treatment solutions. Siete Cerros showed symptoms of severe Al toxicity in solutions with low levels of Mg regardless the salt concentration and the growth period into the treatment solutions. Positive correlations were found between root length and Mg concentrations into the treatment solutions; negative correlations were calculated between root length and aluminum ionic activity into the solution; negative correlations were verified between root length and Al concentration in the top dry matter of the plants and negative correlations were found between the Al concentration in the top dry matter of the plants and the Mg concentration in the treatment solutions. Aluminum toxicity symptoms increased in all studied cultivars by decreasing the Mg concentration and/or the salt concentration, consequently, increasing the aluminum ionic activity and by increasing the growth period in a treatment solution with 10 mg/l of Al3+.
wheat; root length; tolerant and sensitive cultivars; tolerance to aluminum toxicity; aluminum ionic activity; magnesium concentration