Effect of bio-fertilizers and foliar application of nano-silicon on the contribution of dry matter remobilization and current photosynthesis in grain yield of wheat under irrigation withholding conditions

Drought is assumed as one of the most severe abiotic stress factors limiting plant growth and crop production. Drought stress hurts plant growth and productivity which can affect biochemical and physiological responses such as changes in contribution of stem assimilates to grain, current photosynthesis, yield and yield components. Using rhizosphere microorganisms (such as beneficial bacteria and mycorrhiza) (Dimkpa et al. 2009) and application of silicon are an alternative strategy that can improve plant performance under stress environments and, consequently, enhance plant growth through different mechanisms. Thererfore, it seems that application of nano silicon and bio-fertilizers can improve wheat yield under water limitation conditions.

In order to study the effect of bio-fertilizers and foliar application of nano-silicon on the contribution of dry matter remobilization and current photosynthesis in grain yield of wheat under irrigation withholding conditions, a factorial experiment was carried out with three replications at the research farm faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili during 2018-2019. The area is 38° 15′ N latitude, 48° 15′ E longitude, and 1350 m above mean sea level. Climatically, the area is situated in the semi-arid temperate zone with a cold winter and moderate summer. Factors were included irrigation in three levels (full irrigation as control; moderate water limitation or withholding irrigation at 50% of the heading stage; severe water limitation or withholding irrigation at 50% of the booting stage) based on codes 55 and 43 of the BBCH scale; foliar application of nano silicon (foliar application with water as control, 30 and 60 mg.l-1) and bio-fertilizer (no application as control, mycorrhiza application, both application of flavobacterium and pseudomonas, both application of flavobacterium and pseudomonas with mycorrhiza). Mycorrhiza fungi (mosseae) was purchased from the Zist Fanavar Turan Corporation and soils were treated based on method of Gianinazzi et al. (2001). Psedomunas and flovobacterium were isolated from the rhizospheres of wheat by Research Institute of Soil and Water, Tehran, Iran. 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). In this study, morphological traits, leaf area index, total biomass, dry matter remobilization from shoot and stem, contribution of stem assimilates to grain, contribution current photosynthesis in grain, yield and grain yield components of wheat were investigated. Analysis of variance and mean comparisons were performed using SAS version 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.

The results showed that both application of mycorrhiza with flavobacterium and pseudomonas under full irrigation conditions decreased the contribution of dry matter remobilization from shoot (27.33%) and stem (17.70%) in grain yield, but increased the current photosynthesis (305.10 g.m-2) and Contribution Current photosynthesis in grain (72.66%). Also, maximum of grain yield (4593 kg.ha-1) and harvest index (38.4%) were obtained with the application of both bio-fertilizers and foliar application of 30 mg.l-1 nano-silicon under normal irrigation. Maximum leaf area index, total biomass, and yield components were obtained with the combined application of bio-fertilizers and 60 mg.L-1 nano-silicon under full irrigation conditions.

Based on the results of this study, it seems that the application of bio-fertilizers and nano-silicon can be a suitable management factor to increase grain yield of wheat under water limitation.