Proline accumulation, ion homeostasis and antioxidant defence system alleviate salt stress and protect carbon assimilation in bread wheat genotypes of Omani origin

In this study, the responses of bread wheat genotypes of Omani origin to salt stress (40, 80, and 120 mM NaCl) were evaluated to elucidate the salt tolerance mechanism. The tested bread wheat genotypes varied significantly for their responses to different levels of salt stress. A significant decrease in plant growth and carbon assimilation was noted under salt stress and this reduction increased with an increase in salinity levels. However, salinity caused a significant increase in the tissue sodium and chloride, malondialdehyde contents, leaf proline, and activities of antioxidant enzymes. The genotype SIS-12 was least affected for growth and carbon assimilation under all levels of salt stress. This genotype also had the lowest tissue sodium and leaf malondialdehyde contents, and the highest proline and catalase activity under all levels of salt stress. This was followed by genotypes Sayreea and Messani Black whereas the genotypes Bahree, Messani White, Waleedi and Cooley were sensitive to salt stress. The microsatellite loci showed a high value of polymorphism information content (PIC) ranging from 0.73 to 0.87, with an average of 0.81 PIC. The genotypes with higher proline, activities of catalase and superoxide dismutase, and lower tissue sodium and chloride levels were better able to sustain growth under salt stress. These traits and a moderate level of genetic diversity in Omani wheat genotypes can be used in future breeding programs to develop salt-tolerant wheat genotypes.