Key physiological mechanisms involved in salt tolerance by comparing quinoa genotypes of various geographical origins

Abstract

Salinity is the most common problem that limits agricultural productivity in arid and semi-arid regions. One of the promising approaches to cope with salinity problems is the direct utilise of cash halophyte crops. Chenopodium quinoa is regarded as a facultative halophyte with a great potential for cultivation in saline regions. The wide range of geographic distribution of quinoa has resulted in significant genetic diversity in salinity stress tolerance among quinoa cultivars. This study aimed to elucidate the individual mechanisms that confer differences in salt resistance to three quinoa cultivars of different origins, namely, the salaries cultivar "Real", the highland cultivar "CICA-17", and the coastal lowland cultivar "NL-6". The quinoa genotypes, varying in salinity tolerance, were sown in sandy soil and directly irrigated with three water salinity levels (0, 150, and 300 mM NaCl) under greenhouse conditions. Eight weeks after the treatments, Plant growth parameters , leaf Na and K content, and photosynthetic measurements were determined. Seed yield per plant was measured at the end of the experiment. Responses to salinity greatly differed among the three cultivars. Plant seed yield was reduced by 47.1 %, 48.5 %, and 11.7 % in the NL-6, CICA, and Real cultivars respectively, at 150 mM NaCl salinity treatment. The Real plants exhibited distinctly the highest K+/Na + ratio compared to both CICA-17, and NL-6 plants, suggesting a more efficient control mechanism for K+ retention in Real cultivar. Net CO 2 assimilation rates were reduced by 42.8 % and 49.0 % of the control values in NL-6 and CICA-17 cultivars, respectively, versus only 11.7 % for Real plants. When plants were exposed to 300 mM NaCl, all cultivars showed a sharp decrease in physiological traits and seed yield, with a decrease of 71.7 %, 70.4 %, and 42.8 % in the potassium/sodium ratio in leaves and a reduction of 66.0%, 71.0% and 48.0% in the rates of Net photosynthesis and 84.3 %, 82.3 %, 66.8 % decrease in seed yield of NL-6, CICA-17 and Real cultivars, respectively, compared with the control. These results revealed that Real cultivar is a promising candidate in terms of salt-resistance and seed yield compared to either the CICA-17 or NL-6 cultivars.