Relationship between root‐mediated changes and salt tolerance in wheat (Triticum aestivum L.)

Abstract

Salt affected soils have higher concentration of soluble salts or exchangeable sodium to the extent that affects normal growth of crops. Salt-affected soils include saline, sodic and saline- sodic soils. These soils are mostly present in arid and semi arid regions of the globe because in such areas annual rainfall is less than evapo-transpiration. Plants face different types of problems due to the presence of salts. The research work presented in this thesis includes screening of 25 wheat genotypes under saline sodic field conditions. The genotypes selected from these salt affected conditions were further tested in pots and characterized in nutrient solution studies where the salts were artificially applied. Growth reduction occurred under salt stress and genotypes differed significantly in stress treatments. In saline treatment, the genotype 25- SAWSN-12 produced higher shoot fresh and dry weights, and showed lower accumulation of Na+ and Cl- and higher concentration of K+ where as the genotype 25-SAWSN-8 produced lower shoot fresh and dry weights and had lower accumulation of K+ and higher concentration of Na+ and Cl-. The salt tolerant wheat genotype 25-SAWSN-12 maintained better water relations, photosynthetic parameters and showed better oxidative stress tolerance with higher activities of SOD, POD and CAT than the salt sensitive genotype. The seminal and nodal root growth of 25- SAWSN-12 was higher than 25-SAWSN-8. The tolerant genotype also exhibited higher ash alkalinity and the production of organic acids including citric acid, malic acid and tartaric acid than the salt sensitive wheat genotype. These characteristics helped the tolerant genotype 25- SAWSN-12 to maintain better growth under salt-affected conditions than the salt sensitive wheat genotype 25-SAWSN-8. Therefore, the genotype which can maintain higher concentration of K+ and lower concentration Na+ and Cl- tend to grow better in salt affected field conditions. A salt tolerant wheat genotype secretes more root exudates and will acidify its rhizosphere in a better way thus making the rhizosphere conditions favourable for itself even under unfavorable soil conditions. The enhanced enzymatic activity in tolerant genotype will reduce the effect of ROS on plants produced as a result of salt exposure. The genotype 25-SAWSN-12 was promising under salt-affected conditions, and can be recommended to the farmers and may also be used by the breeders for the development of more salt tolerant wheat genotypes. This will help the farmers to reclaim their salt affected rootzone soils by biological means as the rhizosphere acidification will help to improve the soil for better plant growth under salt affected conditions.