Evaluation of some commercial and candidate cultivars of spring wheat (Triticum aestivum L.) for salt tolerance

Abstract

A study was planned to assess the salt tolerance potential of 10 wheat cultivars, five newly developed (S-24, Saher-2006, Inqlab-91, Faisalabad-2008 and Lasani) and five candidate (P.B-18, M.P-65, SH-20, AARI-10, G.A-20). Two salinity levels were (0 mM and 150 mM) applied at three growth stages seedling, tillering and boot stages. This study comprised independent two experiments. The first experiment was performed to screen the 10 wheat cultivars on the basis of biomass production and yield under saline stress. Four wheat cultivars (S-24, Saher-2006, Lasani and AARI-10) were selected on the basis of the results of the first experiment and again grown in the following year for detailed study of physio-biochemical responses under saline stress imposed at different growth stages. Saline stress application at different growth phases caused a marked reduction in biomass production, yield, different gas exchange attributes, photosynthetic pigments and water relation parameters. However, comparatively cvs. S-24 and Saher-2006 showed less reduction in these attributes due to saline application at three growth stages. Less cholophyll degradation, comparatively higher photosynthetic and transpiration rate and leaf turgor were observed due to saline stress imposition at the boot stage. However, it was greater due to salinity imposed at the seedling stage. Furthermore, NaCl applied at three different growth stages markedly increased the endogenous Na+ level and caused reduction in Ca2+, K+, K+/ Na+ and Ca2+/ Na+ ratios. Overall, cvs. Saher-2006 and S-24 maintained higher K+/ Na+ and Ca2+/ Na+ ratios as compared to the other wheat cultivars under salt stress. There was a less decrease in K+/ Na+ and Ca2+/ Na+ ratios under the saline environment developed at the boot stage while maximum at the seedling stage. A significant alteration in different biochemical attributes was observed in all wheat cultivars under saline stress imposed at three growth stages. For example, a substantial increase was observed in H2O2, MDA, soluble proteins, proline, glycinebetaine and activities of different aintioxidants (SOD, POD, CAT, phenolics). Different wheat cultivars showed variation in these biochemicals in response to salt stress applied at different growth stages. Maximum antioxidative enzymes activities were observed in cvs. S-24 and Saher-2006 due to saline stress application at three growth stages. However, cvs, S-24 and Sher-2006 had higher accumulation of GB and proline as compared to the other cultivars (Lasani and AARI-10) under saline stress imposed at early growth stages (seedling and tillering) than at the boot stage. Anatomical studies of four wheat cultivars under saline stress applied at different growth stages showed that cvs. S-24 and Saher- 2006 had thick epidermis of stem and root, greater schlerification in stem and leaf, higher vascular bundle and metaxylem area and greater cortical cell area due to saline stress applied at three different growth stages than the other two cultivars (Lasani and AARI- 10). These anatomical characteristics showed their better adaptability under saline environment in terms of checking water loss, good water storage capacity, and better toxic ion compartmentalization due to large size vacuoles of cortical cells and better water and nutrient transport through vessels. So, it can be inferred that wheat is more prone to adverse effects of saline stress when applied at the early growth stage (seedling) than at later growth stages. Overall, of all wheat cultivars cvs. S-24 and Saher-2006 were more tolerant to saline stress.