Evaluation of yield and grain filling components of triticale (X Triticosecale Witt.) affected by application of mycorrhizal fungi, vermicompost and nano-silicon under water deficit conditions

Drought stress is one of the most important abiotic factors that can limit plant growth and yield. The response of plants to water limitation 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 severe water limitation on plant growth. Among them the use of bio-fertilizers (such as mycorrhizae and vermicompost) and nano-silicon play a key role in yield improvement. The aim of this study was to investigate the effects of irrigation withholding in reproductive stages and nano-silicon and bio-fertilizers application on grain filling period, chlorophyll content and grain yield of triticale.

In order to study the effect of vermicompost, mycorrhizae and nano-silicon on yield and chlorophyll content of triticale under water limitation conditions, 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 in 2020. Experimental factors were included irrigation limitation at three levels (full irrigation as control, irrigation withholding in 50 percent of heading and booting stages as moderate and severe water limitation, respectively), bio-fertilizers application at four levels (no application of bio-fertilizers as control, application of vermicompost, mycorrhizae, and both application of vermicompost and mycorrhizae) and foliar application of nano-silicon (2 g.L-1 of nano-silicon and water-sprayed as control). Sanabad cultivar was used in the experiment with plant density of 400 seed m-2. Chlorophyll and carotenoids content were obtained according to Arnon (1949).To study the grain filling parameters in each sampling, two plants in each pot were taken. The first sampling was taken on day 8 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 75°C for 48 h. A two-part linear model was used to quantifying the grain filling parameters. Total duration of grain filling was determined for each treatment combination by fitting a bilinear model:GW = [a + gfr(daa), ... ... if ... daa<Pm; a + gfr(Pm), ... ... if ... daa≥Pm] 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 grain filling period (EGFD) was calculated from the following equation:EGFD = HGW/GFR Where EGFD, HGW and RGF are effective grain filling period, the highest 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 NLIN DUD procedure. At plant maturity, grain yield in each pot were harvested by five plants per pot. Analysis of variance and mean comparisons were performed using SAS 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 application of vermicompost, mycorrhizae and foliar application of nano-silicon under normal irrigation condition significantly increased chlorophyll a (61.02 percent), chlorophyll b (43.17 percent), total chlorophyll (55.97 percent) and carotenoid (55.8 percent) content, maximum of grain weight (54.78 percent), grain filling period (16.26 percent) and effective grain filling period (46.16 percent) in comparison with no application of bio-fertilizers and nano-silicon under irrigation withholding in booting stage condition. Also, there were a significant increase about 36.78, 45.83, 61.8, 44.11 and 59.52 percent in plant height, ear length, the number of grain per spike, 100 grains weight and grain yield per plant in application of vermicompost, mycorrhizae and foliar application of nano-silicon under full irrigation in comparison with no application of vermicompost, mycorrhizae and foliar application of nano-silicon under irrigation withholding in booting stage condition.

It seems that the application of bio-fertilizers and nano-silicon can increase grain yield of triticale under water limitation conditions due to improving chlorophyll content and grain filling components.