Effect of silicone spraying on assimilate remobilization and yield of two bread and durum wheat under late season water stress

Wheat is one of the major plants cultivated in arid and semi-arid regions and is number one whit respect to planting area and production in the world. Sensitivity of wheat to water stress in not equal in all of the growth stages and flowering stage is very sensitive to water stress, which silicon application could be able to increase the tolerance of wheat to water stress. This research was conducted to investigate the effect of silicon spraying on assimilate remobilization and grain yield of wheat under late season water stress conditions.

In order to investigate the effect of silicon on remobilization and yield of two bread and durum wheat cultivars, under late season water stress, a field experiment was conducted as split factorial experiment in a completely randomized block design with three replicates at Agriculture College and Natural Resources of Darab, Shiraz University, during 2017-2018 growing season. Experimental treatments consisted of water stress in two levels included normal irrigation and water stress at the end of flowering, silicon (Si) spraying at 0, 1, 2, and 3 mM and two wheat cultivars (Chamran and Shabrang). In this research, assimilate remobilization, remobilization contribution and remobilization sufficiency were determined according to Cox et al., (2006) and Papakosta and Gagianas's (1991) methods.

The results showed that the main effects of water stress, cultivars and silicon had significant effects on assimilate remobilization, contribution efficiency, remobilization efficiency, number of seeds per spike, 1000-grain weight, harvest index, biological yield and grain yield. Foliar application of 3 mM Si increased 12.7%, 25.3% and 16% of assimilate remobilization, contribution efficiency, and remobilization efficiency of wheat compared to no Si application, respectively. Also, at 3 mM silicone under water stress the number of seeds per spike and 1000-seed weight increased 43 and 13%, respectively. In normal irrigation conditions, grain yield had a positive and significant correlation with 1000-grain weight (r = 0.545 **), while in water stress conditions, grain yield was had a positive and significant correlation with 1000-kernel weight (0.520**), harvest index (0.404*), biological yield (0.810**) and contribution efficiency (0.459**).

In Chamran cultivar, foliar application of 3mM Si improved assimilate remobilization and remobilization efficiency by 67.2 and 38.7%, respectively, which resulted in 19.7% increase in grain yield of Chamran cultivar compared to Shabrang when plant exposed to water stress. Overall, foliar application of 3 mM silicon could be a suitable approach in improve and increase the wheat grain yield under late season water stress in semi-arid areas.