Physiological responses to salt stress were measured in Chenopodium quinoa, a regionally important halophytic staple crop of Andean South America. In a greenhouse experiment, salt (NaCl) was applied to quinoa varieties, Chipaya and KU-2, and to the model halophyte Thellungiella halophila to assess their relative responses to salt stress. Height and weight data from a seven-week time course demonstrated that both C. quinoa cultivars exhibited greater tolerance to salt stress than the model plant T. halophila in these specific conditions. In a separate growth chamber experiment, two quinoa cultivars (chipaya and ollague) adapted to saline soils and one quinoa cultivar (CICA-17) adapted to a lower elevation were grown hydroponically and evaluated for physiological responses to four salt stress treatments. Tissues collected from the growth chamber experiments were used to obtain leaf water content, tissue ion concentrations, compatible solute concentrations, and RNA for real-time PCR. High levels of trigonelline, a known osmoprotectant, were found to accumulate in the high salt treatment suggesting a key role in salt tolerance of quinoa. The expression profiles of genes involved in salt stress, showed constitutive expression in leaf tissue and up-regulation in root tissue in response to salt stress. These data suggest that quinoa tolerates salt through a combination of salt exclusion and accumulation mechanisms.
Key words: Salt stress, quinoa, Thellungiella halophila, trigonelline, osmoprotectant.
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