Aluminium tolerance of root hairs underlies genotypic differences in rhizosheath size of wheat (Triticum aestivum) grown on acid soil

Summary

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  We found significant genetic variation in the ability of wheat (Triticum aestivum) to form rhizosheaths on acid soil and assessed whether differences in aluminium (Al³⁺) tolerance of root hairs between genotypes was the physiological basis for this genetic variation.
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  A method was developed to rapidly screen rhizosheath size in a range of wheat genotypes. Backcrossed populations were generated from cv Fronteira (large rhizosheath) using cv EGA-Burke (small rhizosheath) as the recurrent parent.
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  A positive correlation existed between rhizosheath size on acid soil and root hair length. In hydroponic experiments, root hairs of the backcrossed lines with large rhizosheaths were more tolerant of Al³⁺ toxicity than the backcrossed lines with small rhizosheaths.
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  We conclude that greater Al³⁺ tolerance of root hairs underlies the larger rhizosheath of wheat grown on acid soil. Tolerance of the root hairs to Al³⁺ was largely independent of the TaALMT1 gene which suggests that different genes encode the Al³⁺ tolerance of root hairs. The maintenance of longer root hairs in acid soils is important for the efficient uptake of water and nutrients.