Variation for aluminium resistance among maize genotypes evaluated with three screening methods

Genetically determined differences in aluminum (Al) resistance exist among plant species and genotypes, and efforts to select and breed maize germplasm with higher resistance to Al have been made worldwide. This work aimed to study genotypic variation for Al resistance in maize genotypes by using three different screening techniques, to compare the results of the screening techniques, and to select genotypes with differential sensitivity to Al for further research on the mechanisms of Al resistance in maize. The effects of Al on various plant characteristics were studied with 10 maize genotypes in a series of experiments that comprised short-term (4 and 14 d) exposures to Al in culture solution (up to 100 µM Al), as well as longer-term (40 d) growth in an acid soil (soil solution pH range 3.4-4.1). Al resistance varied widely among the maize genotypes, as revealed by the different screening methods used. A screening method based on root elongation rate of seedlings growing in culture solution was effective in discriminating resistance to Al. A concentration of 40 µM Al gave the best differential responses among the 10 genotypes studied, causing reductions in root elongation rate of 10 to 68%. The best indicators of differential Al resistance were root characteristics, especially root length. Internal root concentrations of citrate and malate, however, did not reflect plant resistance to Al. The Al resistance rankings established with the screening techniques were consistent and indicated genotypes with contrasting sensitivity to Al to be used in further studies of mechanisms of Al resistance in maize