Effect of Mycorrhiza and methanol on grain filling components, dry matter remobilization and yield of barley under soil salinity conditions

Soil salinity is one of the most important abiotic stresses that can limit plant growth and yield. The response of plants to soil salinity has been evaluated based on genetic, biochemical and morpho-physiological traits. Several strategies have been developed in order to decrease the toxic effects caused by soil salinity on plant growth. Among them the use of bio fertilizers (such as Mycorrhiza) and application of methanol play a key role in yield improvement. The mechanisms that AMF employ to enhance the salt tolerance of plants to grow and develop in saline environments include facilitating water and nutrient absorption through hyphae, maintaining more favorable K+/Na+ ratios to alleviate toxic ions effects. Also, foliar application of methanol is a method which increases crop CO2 fixation. In most cases, 25% of the carbon in C3 plants is used for photorespiration, and the amount of photorespiration can be minimized by the foliar application of methanol because methanol is rapidly metabolized to CO2 in plant tissue. So, the aim of this study was to investigate the effects of methanol and Mycorrhiza application on dry matter remobilization, grain filling components and yield of barley under soil salinity.

An experiment was conducted as factorial based on randomized complete block design with three replications in greenhouse research of Faculty of Agriculture and Natural Resources, University of Mohaghegh Ardabili during 2020. Factors experiment were included salinity in three levels (no application of salinity as control, salinity 35 and 70 mM by NaCl), application of mycorrhiza (no application of mycorrhiza as control, application of mycorrhiza mosseae, mycorrhiza intraradices and both application mycorrhiza mosseae and intraradices) and methanol foliar application in three levels (foliar application with water as control, foliar application 15 and 30% volume of methanol). Foliar application with methanol was done in two stage of period growth (Stem elongation and Flag leaf development). The barley cultivar "Khorram" was used in the experiment with plant density of 400 seeds m-2. To study the grain filling parameters in each sampling, two plants in each vase were taken. The first sampling was taken on day 16 after heading, and other samplings were taken in 4-days intervals to determine the accumulation of grain weight. At each sampling, grains were removed from spikes manually and were dried at 130°C for 2 h. We applied grain dry weight and number to estimate the mean grain weight per sample. Following Borrás and Otegui (2001), we calculated total duration of grain filling for each treatment combination through fitting a bilinear model:= GW = a+ bt0 = t<t0  = a +bt =t>t0 Where GW is the grain dry weight; a, the GW-intercept; gfr, the slope of grain weight indicating grain filling rate; daa, the days after earring; and pm, physiological maturity. Borrás et al. (2004) determined grain filling using a bilinear model. Effective grainfilling period (EGFD) was calculated from the following equation: EGFD = HGW/GFR Where EGFD, HGW and RGF are effective grain filling period, maximum of grain weight (g) and grain filling rate (g.day-1), respectively. Conversely, an increase in grain weight in filling period was calculated using the above-cited equation in statistical software SAS 9.1 via Proc NLIN DUD method. At plant maturity, grain yield in each pot were harvested five plants per pot. 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 (Duncan) test at the 0.05 probability level.

The results showed that both application of mycorrhiza mosseae and intraradices and foliar application of 30% volume of methanol increased the leaf protein content, current photosynthesis and contribution of current photosynthesis in grain yield. But decreased dry matter remobilization from stem, shoot and contribution of dry matter remobilization in grain yield. Also, both application of mycorrhiza mosseae with intraradices and foliar application of 30% volume of methanol under no application of salinity increased root weight and volume (65.12 and 84.14% respectively), plant height (53.15%), spike length (63.63%), 100-seed weight (84.76%), maximum of grain weight (74.32%), grain filling period and effective grain filling period (31.78 and 73.9%, respectively), grain yield (38.52%) in compared to no application of mycorrhiza and methanol under 70 mM soil salinity.

Based on the results, it seems that the application of mycorrhiza and methanol can increase the grain yield of barley under soil salinity by improving photosynthesis and grain filling components.