ENHANCING THE SALT TOLERANCE POTENTIAL OF BELL PEPPER (Capsicum annuum L.) THROUGH EXOGENOUS APPLICATION OF SPERMIDINE IN COMBINATION WITH CALCIUM

Abiotic stresses are the principal threat to crop growth and productivity all over the world. In the irrigated systems one of the most important stresses can be the accumulation of soil salinity which adversely affects the plants, so a comprehensive study was conducted to enhance the salt tolerance potential of bell pepper (Capsicum annuum L.). The experiments were conducted in greenhouse of Institute of Horticultural Sciences, University of Agriculture, Faisalabad. The study comprised of four experiments. The experiments with factorial arrangements were laid out in Completely Randomized Design (CRD) with four replications. Data pertaining to various morphological, physiological, biochemical, enzymatic and ionic parameters were collected and analyzed statistically using standard statistical procedures. In the first experiment, fourteen genotypes of bell pepper were screened out for salinity tolerance on the basis of germination and emergence test by using different salt treatments (2, 4, 6 and 8 dS m-1) along with control (0 dS m-1). Genotypes were categorized on the basis of percent decrease in different measured attributes. On the basis of overall percent decrease ranking table genotypes were grouped into salt tolerant (Zard, Tasty, Super shimla, Aristotle), moderately tolerant (Capistrano, CW-03, Kaka-01, Orable, Yolo wonder, Crusadar) and sensitive ones (PEP-311, Admiral, Lafayette, Colossol). In the second experiment, optimization of spermidine levels was carried out by using two genotypes (Zard, salt tolerant and PEP-311, salt sensitive) of bell pepper. On the basis of different morpho-physiological and ionic attributes, 5 mM spermidine level was found more effective as compared to other levels (4, 6, 7 and 8 mM Spd) for the amelioration of salt stress in both genotypes. In the third experiment, best dose of calcium chloride was optimized for mitigation of salt stress in salt tolerant and salt sensitive genotype of bell pepper. On the basis of measured attributes, 7.5 mM CaCl2 concentration was found more efficient than 5, 10, 12.5 and 15 mM CaCl2 for mitigation of deleterious effects of salt stress in both genotypes. In fourth experiment, combined effect of spermidine and calcium were checked out on morpho-physiological, ionic and biochemical attributes of salt tolerant and sensitive genotypes of bell pepper. Salt stress significantly affected all the measured attributes like morphological (plant fresh and dry biomass, leaf area, seedling shoot and root length), physiological (gas exchange characteristics), water relations (leaf osmotic, water and turgor potential), ionic analysis (Na, K, Ca, Cl contents), enzymatic (POD, SOD, CAT, GPX) and various biochemical (proline, glycinebetaine, total protein and phenolic contents, total soluble sugars) functions of the both genotypes of bell pepper. It was found that combined application of spermidine and calcium (Spd+Ca) enhanced the salt tolerance potential of salt tolerant (Zard) and salt sensitive (PEP-311) genotype of bell pepper. However, Zard responded more towards combined application of spermidine and calcium as compared to PEP-311 under saline as well as non saline conditions. The increase in salt tolerance potential by Spd and Ca also exhibited a correlation with antioxidant activities and organic/inorganic osmolytes accumulation