Morpho-Physiological and Yield Responses of Quinoa (Chenopodium quinoa Wild.) to Foliar Application of Methyl Jasmonate and Salicylic Acid under Drought Stress

Drought condition is one of the most important abiotic stresses through the world. In the first place, the best way to prevent the reduction of crop yields in drought conditions is to use natural compounds that play a key role in growth, development and response to environmental stresses. Quinoa (Chenopodium quinoa Wild.) belongs to the Chenopodiaceae family, a plant with high nutritional value and rich in protein as a future crop. Due to the high resistance to various biotic and abiotic stresses, global demand for quinoa is currently increasing and its global production is less than market purpose.

This experiment was conducted during 2020-2021 cropping season as split plots based on a randomized complete block design with three replications at research farm of Zabol University (UOZ), IR. Iran. The main plot factor was irrigation regimes at three levels: 1- Irrigation equal to 100% crop water requirement (control), 2- Deficit irrigation equal to 75% crop water requirement (mild stress), 3- Deficit irrigation equal to 50% crop water requirement (severe stress) and six levels of foliar application were assigned to the sub plot: Control (sprayed with distilled water without ethanol), 70% ethanol, 0.5 mM SA, 0.5 mM MeJA, 1 mM SA and 1 mM MeJA. In this study plant height, stem diameter, panicle dry weight, root dry weight, dry matter, seed yield, harvest index, stomatal conductance, electrolyte leakage, chlorophyll florescence and water use efficiency were measured. Determination of irrigation interval and crop water requirement was based on CROPWAT 8.0 software and Penman-Mantis equation. For plant coefficients used FAO default data. Irrigation planning was determined with 85% efficiency and water volume of each plot calculated using a digital water meter.

The results revealed that the irrigation 50% crop water requirement (severe stress), regime increased electrolyte leakage, water use efficiency and root dry weigh, whereas it did not significantly affected Fv/Fm, stomatal conductance and harvest index. The highest plant height with mean 144.02 cm was obtained from 100% crop water requirement and 1 mM SA and the lowest with a reduction 71.5% was obtained at 50% crop water requirement and no spraying conditions. Quinoa had 54.3% higher seed yield than control under drought stress conditions owing to unaffected Fv/Fm and stomatal conductance and less electrolyte leakage. Spraying 1 mM MeJA and SA increased chlorophyll fluorescence (22.4%), stomatal conductance (53.4%) and harvest index (38%). In severe drought stress (supply 50% crop water requirement), foliar application significantly increased the water use efficiency (from 0.2 to 1.1 kg m-3). In severe drought stress, increased quinoa seed yield was due to to increase in water use efficiency. According to the results drought stress decreased physiological and seed yield traits, 1 mM MeJA could increase the seed yield (292.93 g m-2) and then partially compensated for the reduction caused by drought stress. Also, seed yield with mean 281.96 g m-2 was in the second rank at 1 mM MeJA application and 75% crop water requirement (mild stress) conditions. Fv/Fm ratio was not significantly affected in drought stress. The highest harvest index was observed in 1 mM MeJA and SA compared to the control. Therefore, for minimizing the effect of drought stress, we could recommend the use of 1 mM MeJA.

The least stress treatment for quinoa economic yield supply was 100% crop water requirement (control) and 1 mM MeJA application. Also the average seed yield (281.96 g m-2) was at the second rank, in 1 mM MeJA and 75% crop water requirement (mild stress) treatment. It seems that stress tolerance mechanisms study and MeJA foliar application is necessary, especially in areas with less water and we need to develop crops that possible to produce high quantity with require low water in farm.