Effects of vermicompost, humic acid and seed inoculation with Flabacterium on yield, chlorophyll fluorescence indices and some physiological traits of triticale under soil salinity conditions

Soil salinity is one of the most serious limiting factors for crop growth and production in the arid and semi-arid regions. 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), vermicompost and humic acid play 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. Vermicompost plays a very important role in plant nutrition and soil health. So, it seems that application of bio fertilizers such as PGPR, vermicompost and humic acid can improve crop yield under soil salinity stress. Therefore, the aim of this study was evaluation of yield, chlorophyll fluorescence indices and some physiological traits of triticale in response to humic acid and bio fertilizers application under soil salinity conditions

In order to study the effects of vermicompost, humic acid and seed inoculation with flavobacterium on yield, chlorophyll fluorescence indices and some physiological traits of triticale under soil salinity conditions, an experiment was conducted as factorial based on randomized complete block design with three replications in greenhouse research of the Faculty of Agriculture and Natural Resources, the University of Mohaghegh Ardabili during 2020. Experimental factors were included salinity levels (non-application of salinity as control, application of 50 and 100 mM salinity by NaCl), and bio-fertilizers application (no application of bio-fertilizers as control, application of vermicompost, seed inoculation with Flavobacterim, both application vermicompost and Flavobacterim) and foliar application humic acid (foliar application with water as control and foliar application of 2 g.l-1 humic acid). vermicompost was purchased from the Gilda corporation. Flavobacterim was isolated from the rhizospheres of wheat by Research Institute of Soil and Water, Tehran, Iran. The triticale cultivar "SANABAD" was used in the experiment with plant density of 400 seeds m-2. For inoculation, seeds were coated with gum Arabic as an adhesive and rolled into the suspension of bacteria until uniformly coated. The strains and cell densities of microorganisms used as PGPR in this experiment were 1×108 colony forming units (CFU).  Relative water content: Weight of fresh leaf was measured just after detached from the plants then taken turgid weight after leaf was incubated in distilled water for 24 h to obtain a full turgidity. Dry weight of leaf was measured after it was dried at 60°C for 24 h in an oven. Relative water content was measured according to the following formula (Chelah et al. 2011). RWC (%) = [(FW-DW) / (TW-DW)] × 100 Where, RWC, FW, DW and TW are relative water content, fresh weight, dry weight and turgid weight respectively.Chlorophyll content: A portable chlorophyll meter (SPAD-502; Konica Minolta Sensing, Inc., Japan) was used to measure the leaf greenness of the wheat plants. Quantum yield: The quantum yield was measured by the uppermost fool expanded leaf using a fluorometer (chlorophyll fluorometer; Optic Science-OS-30 USA).Electricalconductivity: Electrical conductivity was calculated by following the standard method of Jodeh et al. (2015). Electrical conductivity (EC) values were measured at room temperature of 23±1 °C using an electrical-conductivity meter. At plant maturity, grain yield in each pot were harvested five plants per pot. Statistical analysis: Analysis of variance and mean comparisons were performed using SAS ver 9.1 computer software packages. The main effects and interactions were tested using the least significant difference (LSD) test at the 0.05 probability level.

Means comparison showed that the both application of vermicompost, Flavobacterim and foliar application of 2 g.l-1 humic acid under no salinity condition increased maximum fluorescence (22.53%), variable fluorescence (94.69%), quantum yield (58.88%), chlorophyll index (28.91%), nitrogen index (3.88%), relative water content (50.48%)of flag leaf and grain yield (69.56%) in comparison with no application of bio-fertilizers and humic acid under 100 mM soil salinity. No application of biofertilizers and foliar application of humic acid at salinity of 100 mM increased the electrical conductivity and minimum fluorescence (F0) the flag leaf.

It seems that application of bio-fertilizers and humic acid can increase grain yield of triticale under soil salinity conditions due to improving chlorophyll fluorescence and some physiological traits.