Salt Tolerance in the Triticeae: The Contribution of the D Genome to Cation Selectivity in Hexaploid Wheat

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Abstract
Inorganic cation concentrations were measured in shoots of hexaploid bread wheat (Triticum aestivum L.) and its presumed ancestors grown at 100 mol m−3 external NaCl. Aegilops squarrosa and T. aestivum had high K/Na ratios while T. dicoccoides and Ae. speltoides had low K/Na ratios. T. monococcum although having a high K/Na ratio, had the highest total salt load of the five species tested. The effect of the D genome (from Ae. squarrosa) was further investigated in seedlings of synthetic hexaploid wheats, and was again found to improve cation selectivity. Different responses were obtained from root and shoot tissue in this experiment. One synthetic hexaploid and its constituent parents were grown to maturity at 100 mol m-3 NaCl and the yields recorded. Despite complications due to increased tillering in the stressed hexaploid, it was possible to show that the addition of the D genome enhanced yield characteristics in the hexaploid wheat. An experiment with synthetic hexaploids derived from the tetraploid wheat variety “Langdon” and several Ae. squarrosa accessions revealed differences in vegetative growth rates between the different synthetic hexaploids in the presence or absence of 150 or 200 mol m−3 external NaCl. The possibility of transferring salt tolerance genes from Ae. squarrosa to hexaploid wheat using synthetic hexaploids as bridging species is discussed.