Tolerance to combined boron and salt stress in wheat varieties: Biochemical and molecular characterization

Plants' tolerance to stresses, particularly abiotic, is an important area of research, particularly in agriculture. Here, we studied the combined effect of excess boron (B) and salinity on three wheat varieties viz., KRL 35, KRL 210 and HD 2009. Root samples were collected 20 days after imposing different treatments, namely Control, 50 and 100 ppm B + 60 mM NaCl, respectively; and 50 and 100 ppm B + 100 mM NaCl, respectively in a hydroponic system. Results indicated that length, fresh and dry weight of root and shoot consistently decreased with increasing concentration of B and salt in the nutrient medium. These changes were accompanied by significant reductions in soluble sugars and proteins in roots, whereas proline content increased. The KRL 35 (salt tolerant variety) showed 5 specific polypeptides of 89.13, 53.4, 46.21, 32.35 and 31.10 kDa. Likewise, KRL 210 (moderately salt tolerant) showed de novo synthesis of 53.4 and 19.13 kDa, whereas three specific polypeptides (24.05, 19.13 and 17.52 kDa) appeared in HD 2009 (salt sensitive). Synthesis of the common polypeptide 25.12 kDa was observed with increase in stress treatments in all three varieties. Enhanced expression of 25.12 kDa proteins, particularly in the sensitive variety induced protein synthesis under excess boron and salt stress conditions. Thus, altered and enhanced expression of proteins might be responsible for the survival and growth of plants under excess B and NaCl affecting the functional capabilities of seeds in the stress environment. Appearance of new polypeptide(s) or their disappearance might be related to the genotypic stress tolerance or sensitivity.