Heat Stress Resulting From Late Sowing Impairs Grain Yield and Quality of Quinoa Genotypes Facing Drought and Salt Stress Under Field Conditions

Climate change is causing drastic reduction in crop yields around the globe due to increase in soil salinity, drought and heat stress. Quinoa (Chenopodium quinoa Willd) is regarded as a very significant food security crop considering the climate change scenario. Two quinoa genotypes (Puno and Titicaca) were cultivated on salt affected soil under drought stress with different sowing dates. Compared with early sowing, late sowing combined with salinity and drought stress caused drastic decline in plant growth and grain yield due to imposition of heat stress. Plant biomass and grain yield decreased by 26% and 39% in Puno, and by 34% and 49% in Titicaca under late sowing accompanied by salt and drought stress. Relative water contents and stomatal conductance of leaves declined in the same trend in both genotypes. Shoot Na⁺ concentration was the highest whereas K⁺ concentration was the lowest in both genotypes when drought and salt stress were combined under late sowing. Grain minerals (Ca, Mg, Fe, Zn, Cu, K, P, N and Mn) and dietary contents (protein, lipids, carbohydrates and fibre) were decreased more under the combination of salinity and drought for late sowing as compared to early sowing. When salinity and drought stress were combined under late sowing, the contents of H₂O₂ and TBARS were 1.9 and 2.2-fold higher in Puno and 2.4 and 2.6-fold higher in Titicaca, respectively. The oxidative stress was mitigated by enhanced activities of antioxidant enzymes (CAT, SOD and POD) more in Puno than Titicaca. Plant biomass and grain yield were higher in Puno with better grain quality than Titicaca. Hence, this genotype should be cultivated on salt affected soils facing drought and high temperatures.