Feasibility of quinoa production under deficit irrigation and glycine betaine foliar application

Abiotic environmental stresses such as drought and salinity are important factors in reducing crop yield in many parts of the world (Muscolo et al., 2016). Water scarcity is the most important factor in reducing the production of crops in arid areas. Therefore, it is necessary to pay attention to the sustainable use of water resources, especially in arid and semi-arid regions (Dabhi et al., 2013; Samadzadeh et al., 2020). Introducing new drought-tolerant crops is the main strategy for sustainable crop production in arid regions (Samadzadeh et al., 2020). Besides, deficit irrigation and foliar application of osmolyte compounds such as glycine betaine can be considered to reduce the effect of drought stress on plant growth and yield (Fallahi et al., 2015; Tian et al., 2017).

In this experiment, the effects of water availability and foliar application of glycine betaine (GB) were studied on the growth and yield of quinoa. The experiment was carried out as factorial based on a complete randomized block design with three replicates in Sarayan, south Khorasan province, Iran. Experimental factors were (1) irrigation management regimes (irrigation after 70, 140, and 210 mm pan evaporation) and (2) GB foliar application (0 zero or distilled water and 150 mg. l-1).

There were no significant differences between irrigation levels in terms of many vegetative and reproductive parameters such as plant height, plant dry weight, number of panicles per plant, panicle length, and its dry weight. An increase in water stress severity caused a reduction in biological yield and 1000-grain weight, but seed yield did not decrease. GB application increased the values of plant dry weight, biological yield, chlorophyll index (SPAD), and the number of panicles per plant, while reduced reducing seed yield. Interaction results of experimental factors revealed that the highest biological yield (2533.3 kg ha-1) was obtained by GB and irrigation after 70 mm pan evaporation, while the lowest value (1433.3 kg ha-1) was gained by the no-GB and 210 mm pan evaporation. The highest seed yield values were obtained by 70 and 210 mm pan evaporation (250.7 and 245.4 kg ha-1, respectively) combined with the no-GB application. In general, due to the scarcity of water resources in arid areas, quinoa irrigation after 210 mm pan evaporation can be recommended.

Quinoa had an acceptable resistance to drought stress. Seed yield in this experiment was much lower than the plant's genetic potential, which could be due to improper planting date and density. Therefore, research on other quinoa cultivars, other planting dates, and foliar application of glycine-betaine at other concentrations and times can complement the results of the present experiment.