Quinoa (Chenopodium quinoa Willd.), traditionally called the mother of grains, has the potential to grow under high temperatures and drought, tolerating levels regarded as stresses in other crop species. A pot experiment was conducted in a climate chamber to investigate the potential of quinoa tolerance to increasing drought and temperature. Quinoa plants were subjected to three irrigation and two temperature regimes. At low temperature, the day/night climate chamber temperature was maintained at 18/8 °C and 25/20 °C for high temperature throughout the treatment period. The irrigation treatments were full irrigation (FI), deficit irrigation (DI) and alternate root‐zone drying (ARD). FI plants were irrigated daily to the level of the pot's water‐holding capacity. In DI and ARD, 70 % water of FI was applied either to the whole pot or to one side of the pot alternating, respectively. The results indicated that plant height and shoot dry weight significantly decreased by ARD and DI compared to FI treatment both at low and at high temperatures. However, plants in ARD treatment showed significantly higher plant height and shoot dry weight compared to DI especially at higher temperature, which is linked to increased xylem ion content. Higher quinoa plant growth in ARD was associated with increase in water‐use efficiency (WUEi) due to higher abscisic acid concentration and higher nutrient contents compared to DI. From results, it can be concluded that quinoa plant growth is favoured by high temperature (25/20 °C) and ARD is an effective irrigation strategy to increase WUE in drought prone areas.
Quinoa is a facultative halophytic seed crop of increasing interest worldwide. Its performance declines under high salinity but can be improved by using halotolerant plant growth-promoting bacteria (PGPB) containing multi-traits, i.e. ACC-deaminase activity, exopolysaccharide secretion and auxin production. This study focussed on improving the productivity of quinoa through the use of six plant growth-promoting bacterial strains (both endophytic and rhizosphere). These were screened by conducting osmoadaptation assay, and the two most halotolerant strains (Enterobacter sp. (MN17) and Bacillus sp. (MN54)) were selected. These two strains were evaluated for their effects on growth, physiological characters and yield of quinoa. At the five leaf stage plants were irrigated with saline water having either 0 or 400 mM NaCl. The results indicated that saline irrigation significantly decreased the growth of quinoa, whereas inoculation of plants with MN17 and MN54 mitigated the negative effects of salinity by improving plant water relations and decreasing Na+ uptake, which consequently, reduced osmotic and ionic stress. Strain MN54 performed better than MN17, which might be because of its better growth promoting traits and higher rhizosphere colonisation efficiency than MN17. Our results suggest that growth and productivity of quinoa could be improved by inoculating with highly tolerant PGPB strain in salt-affected soils.
Abiotic stresses such as drought and salinity constantly threaten food security. Biochar as a soil amendment has the potential to ameliorate soil and alleviate drought and salinity stress. Multiple studies have been conducted to evaluate the effect of biochar in alleviating independent drought or salinity stress. However, the potential of biochar in mitigating the combined drought and salinity stress on plants has not been studied so far. Therefore, a pot experiment was conducted in the climate-controlled chamber with the objective to investigate the effect of biochar on growth, physiology, and yield of quinoa under independent and combined drought and salinity stress. Quinoa plants were subjected to three irrigation treatments i.e., full irrigation (FI), deficit irrigation (DI), and alternate root-zone drying irrigation (ARD), two saline water treatments (0 and 400 mM) and two levels of biochar (0% and 5% by weight). In the FI treatment, plants were irrigated daily to maintain pot water-holding capacity. In limited irrigation treatments, 70% water of FI was applied either to the whole pot in DI or to one side of the pot alternating in ARD, respectively. The results showed that combined drought and salinity stress drastically affected growth and performance of quinoa compared to the independent drought or salinity stress. However, soil amendment with biochar had positive effect in mitigating both independent and combined effect of drought and salinity on quinoa plants. Furthermore, biochar amendment in ARD under salinity significantly enhanced plant height, shoot biomass, and grain by 11.7%, 18.8%, and 10.2% as compared with DI under salinity, respectively. In addition, leaf photosynthetic rate (An) and stomatal conductance (gs) decreased under limited saline irrigation. Moreover, the interactive effect of biochar and ARD efficiently adjusted the balance between chemical signal (leaf ABA) and hydraulic signal (leaf water potential). Thus, intrinsic water use efficiency (WUEi) and yield in ARD were significantly enhanced compared to DI, especially under salinity stress. Overall, biochar in combination with ARD might be a wise approach for sustaining crop productivity in salt affected and drought stressed areas of the world to ensure food security.
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