Abstract
The ability of plants to exclude sodium from the shoot is one of the major components of salinity tolerance. In this study, considerable variability in sodium exclusion within different species is demonstrated. The diploid species T. monococcum revealed a large (50-fold) variability in sodium exclusion in contrast to T. urartu, which was significantly less variable (10-fold). These species with the A genome are known to be salt sensitive, whilst T (Aegilops) tauschii, a diploid species with the D genome, was very salt tolerant, but had only moderate variability in sodium exclusion (10-fold). The tetraploid species T turgidum ssp. durum (both cultivated and landraces) and wild emmer T dicoccoides (all with the AB genome) showed a range of variability in both salinity tolerance and sodium exclusion. The general pattern (from most sensitive and with highest Na+ accumulation) was as follows: durum (cultivated) < durum (landraces) < wild emmer. Cultivated durum wheats had minimal or no variability, whereas landraces of durum wheats had greater variability, two excellent genotypes having been identified which combine very low sodium accumulation with very high salinity tolerance. Wild emmer was extremely variable. Hexaploid bread wheat, T aestivum with the ABD genome, is known to be more salt tolerant, having an effective mechanism for sodium exclusion but only low variability.