The Effects of Some Biofertilizers and Nano Iron-Silicon Oxide on Yield and Grain Filling Components of Triticale (Triticosecale Wittmack) under Water Limitation Condition

In arid and semi-arid regions, drought stress as the main factor and salinity stress as a secondary factor decreases plant growth and yield. Water limitation can damage pigments and plastids, and reduce chlorophyll index, rate, and grain filling period. Several strategies have been developed to decrease the toxic effects caused by environmental stresses on plant growth. Among them, the use of bio-fertilizers such as plant growth-promoting rhizobacteria (PGPR) and also nanoparticles such as nano iron-silicon oxide 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. It seems that application of nanoparticles and biofertilizers can improve triticale yield under water limitation conditions.

To study the effects of bio-fertilizers and nano silicon-iron oxide on the quantitative yield and grain-filling components of triticale under water limitation conditions, a factorial experiment was conducted based on randomized complete block design with three replications at the research farm of the faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili during 2021. The experimental factors included irrigation in three levels (full irrigation as control, irrigation withholding at 50% of the heading stage based on codes 43 of the BBCH scale; irrigation withholding at 50% of the booting stage based on codes 55 of the BBCH scale), as severe and moderate water limitation respectively, application of biofertilizers in four levels (no application of biofertilizers as control, application of Azospirilum, Pseudomonas, both application Azospirilum and Pseudomonas) and nanoparticles foliar application at four levels (foliar application with water as control, nano iron oxide foliar application, nano silicon, both foliar application nano iron-silicon oxide). The strains and cell densities of microorganisms used as PGPR in this experiment were 108 bacteria per milliliter (108 cfu.ml−1). A two-part linear model was used to quantify the grain-filling parameters. In this study, anthocyanin, flag leaf protein, chlorophyll index, grain filling components, and yield of triticale were investigated. Chlorophyll Index was calculated by a chlorophyll meter (SPAD-502; Konica Minolta Sensing, Inc., Japan). Grain dry weight and number were used to calculate the average grain weight for each sample. The total duration of grain filling was determined for each treatment combination by fitting a bilinear model: 
Where GW is the grain dry weight; a, the GW-intercept; b, the slope of grain weight indicating grain filling rate; t, the days after earring; and t0, physiological maturity. The effective grain filling period (EGFD) was calculated from the following equation:EGFD = the highest grain weight (g)/rate of grain filling (g day-1).

The results showed that the both application of biofertilizers and foliar application of nano iron-silicon oxide in full irrigation, increased maximum grain weight (56.07%), grain filling period, and Effective grain filling period (22.29 and 48.43% respectively), chlorophyll index (45.11%) and flag leaf protein (64.75%), plant height (49.31%), number of grains per spike (70.58%), spike length (53.75%), 1000 grains weight (64.9%) and grain yield (43.28%) in compared to no application of biofertilizers and no foliar application under severe water limitation. Severe water limitation increased the content of anthocyanin, but the application of biofertilizers and foliar application of nano silicon-iron oxide decreased its content.

Based on the results of this study, it seems that application of both applications of Azospirilum and Pseudomonas and foliar application of nano iron-silicon oxide can be applied as a proper method for increasing grain yield of triticale under water limitation conditions.