Study the interaction of cycocel and bio- fertilizers on yield and some agro-physiological traits of wheat under soil salinity condition

Introduction Soil salinity is one of the most serious limiting factors for crop growth and production in the arid and semi-arid regions due to increasing use of poor quality of irrigation water. Salt stress is known to affect many physiological activities related to the accumulation of ions and osmolytes such as proline. Several strategies have been developed in order to decrease the toxic effects caused by high salinity on plant growth. Among them, use of bio-fertilizers such as plant growth promoting rhizobacteria (PGPR) plays a very important role in yield improvement. Inoculation of plants with native suitable microorganisms may decrease the deleterious effects of environmental stresses and increase stress tolerance of plants by a variety of mechanisms, including synthesis of phytohormones such as auxins, cytokinin and gibberellins, solubilization of minerals like phosphorus, production of siderophores and increase in nutrient uptake, N2 fixation. Cycocel is an essential growth regulator for plants that reduced concentration of gibberellins and interfere with the concentration of other plant hormones such as cytokinins, ethylene, and abscisic acid, which can affect physiological processes. Better understanding of wheat l responses under salinity may help in programs in which the objective is to improve the grain yield under salinity levels. Therefore, the aim of this study was to evaluate the effects of bio fertilizers and cycocel on yield and some agro-physiological traits of wheat under salinity stress conditions. Materials and Methods In order to study the interaction cycocel and bio- fertilizers on yield and some agro-physiological traits of wheat at soil salinity condition, a factorial experiment based on randomized complete block design with three replications was conducted in research greenhouse of the Faculty of Agriculture, University of Mohaghegh Ardabili in 2015 growing season. Experimental factors were soil salinity at four levels (0 as control, 30, 60 and 90 mM) as NaCl and seed inoculation with bio- fertilizers in four levels (without inoculation as control, seed inoculation with Azotobacter chrocoocum strain 5, Pseudomonas putida strain 186 and Azotobacter+ Pseudomonas) and foliar application of cycocel at three levels (0, 600, and 1000 mg.L). Results The results showed that the effects of salinity, cycocel and bio-fertilizers were significant on grain filling period, grain yield and yield components. The highest grain yield (2.47 g) was obtained from foliar application of 1000 mg.L cycocle × seed inoculation with Azotobacter +Pseudomonas and the least of it (1.98g) was obtained to non-application of cycocle, non-inoculated seed treatment. Interaction effect between salinity and bio fertilizers showed that the highest grain yield (2.65 g per plant) was obtained in no salinity with Azotobacter+ Pseudomonas application and the least it (1.74 g per plant) was obtained in the highest salinity level (90 Mm) and without application of bio fertilizers. Foliar application of 1000 mg.L cycocel, seed inoculation with Azotobacter + Pseudomonas under no salinity condition had the highest ear length (10.25 cm), 100 grain weight (5.3 g) and grain filling period (43.26 days). Maximum of grain filling rate (0.002 g/day) was obtained in inoculation with Azotobacter +Pseudomonas under no salinity condition. Leaf area index increased slowly at all treatment combinations until 35 days after sowing (DAS), then increased rapidly till 65 DAS. Then it decreased till harvest time due to aging of leaves. The highest leaf area index (LAI) was obtained in 65 DAS and Azotobacter+ Pseudomonas application and without application of cycocel and salinity. The least it was obtained in application of 1000 mg.L cycocel and without application of bio fertilizer at the highest salinity level. 30 and 60 mM salinity levels had little effect on chlorophyll content and stomatal conductance. The highest level of cycocel and seed inoculation with Azotobacter+Pseudomonas showed the highest SPAD and stomata conductivity under no salinity stress. Conclusion Generally, it can be suggested that foliar application of 1000 mg.lit-1 cycocel and seed inoculation with Azotobacter+Pseudomonas increased about 20% from grain yield in comparison with control and both inoculation of Azotobacter+Pseudomonas compensated about 15% of yield reduction due to salinity.