Expression level of NHX1 and SOS1 genes is key to high salt tolerance of ancient emmer wheat: implications to tackling salt stress penalties of wheat yield.

Aggravation of salinity is a world-wide concern and the applicability of ancient wheats towards tackling this concern has been neglected so far. This study aims to unravel the molecular-physiological basis of salt response in ancient emmer and spelt wheats. Effects of prolonged salt exposure (0, 75, and 150mM NaCl) on 18 modern and ancient tetraploid and hexaploid wheat genotypes were initially investigated in a pot experiment. Responses of a selection of four genotypes in a field experiment and expression of SOS1 and NHX1 ion-transporter genes in a hydroponic experiment were then assessed under 150mM NaCl. Salinity led to suppressions in relative water content (RWC), chlorophyll, carotenoids, K+ , grain yield, and biomass, though it increased Na+ , proline, H2 O2 , malondialdehyde, and activity of antioxidative enzymes. Accumulation of Na+ in the ancient emmer genotypes was substantial. But, emmer genotypes suffered less from salinity, as they maintained chlorophyll, biomass, and grain yield/plant. Emmer outranked durum, bread, and spelt wheats in terms of expression of SOS1 and NHX1 ion-transporter genes, confirming possession of an enhanced Na+ compartmentalization capability. These findings indicate that emmer wheat harbors an efficient molecular mechanism to tolerate salt and implies applicability in tackling salt stress damage to the wheat's grain yield.