Influence of Seed Priming on the Performance of Barely Varieties Under Late Sown and Abiotic Stress Conditions

Abstract

Abiotic stresses affect plant productivity by modulationg various physiological and biochemical processes. Studies were performed to evaluate the influence of seed priming on the performance of barley varieties under late sown and abiotic stress conditions. For this purpose, a series of experiments was conducted in field and green house of University of Agriculture, Faisalabad, and glass house of Texas A&M University, USA. In first pot experiment, seeds of two barley varieties (viz. Haider-93 and Frontier-87) primed with water (hydropriming), CaCl2 solution (osmopriming) and Enterobacter sp. strain FD17 culture (biopriming) were sown in pots. After seedling establishment, drought levels (viz. 80, 60 and 40% water holding capacity) were imposed. In second pot experiment, same varieties and seed priming treatments were followed except after seedling establishment salinity levels (viz. 50, 100 and 150 mM NaCl) were imposed. Third experiment was carried out in hydroponics. Seedlings were raised in sand filled polythene bags by using same varieties and seed priming treatments. After stand establishment seedlings were transplanted in hydroponics then, osmotic (-0.8 MPa using PEG) and ionic (-0.8 MPa using NaCl) stresses were imposed. In fourth experiment, same procedure was followed as in the third experiment except cadmium (Cd) toxicity stress levels (viz. 0, 8 and 12 mg L-1 water) were imposed. In fifth experiment, seeds of USA cultivar Solum were primed with water (hydropriming) and CaCl2 (osmopriming), and sown in pots. At reproductive stage two levels of heat stress viz. control (25/18°C day/night) and heat stress (35/25°C day/night) were applied. In all pot and hydroponics experiments dry seed was taken as control. The pot and hydroponics experiments were carried out using completely randomized design (CRD) with factorial arrangement having four replications, except fifth experiment in which six replications were used. In sixth experiment, same varieties and seed priming treatments, as in first pot experiment, were followed and sown in field at November 30 and December 30. The experiment was conducted by using randomized complete block design (RCBD) with split-split plot arrangement having four replications. In first and second experiments, drought and salinity decreased plant growth, yield and chlorophyll contents, and perturbed the water and nutrient relations; while, increased accumulation of osmolytes and lipid peroxidation in both barley varieties, as compared to control. Moreover, salinity increased the sodium (Na) accumulation while decreased potassium (K) accumulation. However, seed priming improved plant growth, yield, tissue water status, cell membrane stability, chlorophyll contents and accumulation of phenolics, total soluble proteins, free proline and glycine betaine contents while decreased the malondialdehyde (MDA) content in both varieties under stressed conditions, as compared to unprimed control. The gretest improvement in yield under drought was caused by biopriming; whereas, under moderate and severe salt stress by biopriming and osmopriming, respectively. Moreover, biopriming improved the grain zinc (Zn), manganese (Mn) and boron (B) contents. In third and fourth experiments, osmotic, salt as well as Cd stress decreased the seedling growth and dry biomass in both varieties while increased the osmolytes and lipid peroxidation, as compared to control. Moreover, NaCl salt stress and Cd stress increased Na and Cd contents in barley, respectively. However, seed priming enhanced seedling growth, fresh and dry biomass, chlorophyll contents, phenolics, total soluble proteins, free proline and glycine betaine contents while decreased MDA, Na and Cd contents under stressed conditions, as compared to unprimed control. Under osmotic and Cd stress biopriming was most effective, while, under salt stress osmopriming was superior in improving barley performance. In fifth experiment, terminal heat stress hampered the plant growth, yield, leaf gas exchange and chlorophyll photochemistry while increased the phenolics and lipid peroxidation, as compared to control. However, seed priming improved the photosynthesis, stomatal conductance, carboxylation use efficiency (CUE), quantum yield of photosystem II (QY), electron transport rate (ETR), chlorophyll contents, phenolics and cell membrane stability while decreased MDA content under terminal heat stress, as compared to unprimed control, and osmopriming was superior in this regard. In sixth experiment, late sowing caused a reduction in emergence, growth, grain yield, dry matter accumulation, grain filling duration, chlorophyll contents, and grain crude protein and starch contents in both barley varieties, as compared to optimum sowing time. However, seed priming improved emergence, plant height, crop growth rate (CGR), total dry matter accumulation (TDM), leaf area index (LAI), grain filling rate, yield and related traits, and grain crude protein and starch contents under both optimum and late sowing, as compared to unprimed control. The greatest improvement was caused by osmopriming followed by biopriming. The economic analysis showed that late sowing decreased economic returns as well as benefit cost ratio (BCR) which was improved by seed priming treatments. Among all, biopriming caused maximum improvement in BCR and marginal rate of return (MRR). In all pot and field experiments, variety Haider-93 performed better than Fronteir-87. In conclusion, abiotic stresses and late sowing decreased the plant growth and yield by negatively affecting plant physiological processes. However, performance of barley varieties was effectively improved by seed priming treatments under stressed conditions by improving the water relations, nutrient relations, osmolytes accumulation, photosynthesis, chlorophyll contents and decreasing the lipid peroxidation under stressed conditions.