Biochar, salts phytoextraction, genotypes, spinach, salt bladders.

Soil salinization is one of the factors that reduces productivity in the arable lands. Based on this, the search for crops tolerant to salinity/sodicity has been intensifying. Quinoa (Chenopodium quinoa Willd.) is a facultative halophyte, with high nutritional value capable of mitigating hunger. Spinach (Spinacia oleracea L.), despite being a glycophyte, has the genetic potential to tolerate salinized soils. This work tested two quinoa genotypes (CPAC 09 and CPAC11 - EMBRAPA Cerrados) and spinach (cv. Gazelle), in saline-sodic soils in four experiments. Two experiments were carried out in a greenhouse, with quinoa (genotype CPAC 09), in the winter and summer seasons in Brazil, in three soils (two saline and one non-saline) found in the semi-arid region of Pernambuco (Cambisol, Fluvisol, and Planosol), under the addition of rice husk biochar – RHB – (0, 10, 20, 40, 60, 80 and 100 t ha-1), in randomized blocks and four replications. Soils chemical and physical attributes were evaluated, and biometric, nutritional, and enzymatic analysis were carried out on plants. In winter, the quinoa survival rate was 100% and in summer, under lower biochar doses and in saline soils, plant survival was 25 to 50%. At higher doses (80 and 100 t ha- 1) the survival rate was 50 to 100% depending on the soil. RHB reduced pH, ECe, and SAR in alkaline and saline soils and increased pH in acidic soil. RHB was also a source of K+, being also responsible for the reduction of BD and increase in Ksat in sandy soils, negatively affecting the Ksat of the Fluvisol, due to its interaction with fine sand and silt in high concentrations. The improvement in the soils chemical and physical attributes favored the development of quinoa, increasing its biomass and the K+/Na+ ratio. For CPAC 09, the phytoextraction potential followed the order of K>Cl>Mg>Ca>Na in winter, and K>Cl>Mg>Na>Ca in summer. The spinach was subjected to water levels of 2 and 25 dS m-1, in four replications. In the third experiment, two genotypes of quinoa (CPAC 09 and CPAC11) and spinach (cv. Gazelle) were evaluated under saline waters application (2, 25, 40, and 55 dS m-1), in randomized block design and four replications. Chemical analyses were carried out on soils and also biometric, nutritional, and physiological analysis on plants. For quinoa, there was a reduction between 50 and 60% in grain yield between ECw of 2 and 25 dS m-1 and of more than 95% under ECw of 55 dS m-1. For spinach, shoot biomass reduction was 80% between ECw of 2 and 25 dS m-1. After the treatment’s application, the soils showed an increasing concentration of salts, mainly Na+ and Cl-, increasing the content of these elements in plant tissues. The crops showed a high salt tolerance potential in saline soils, surviving under ECe between 25-30 dS m-1 (spinach), and more than 65 dS m-1(quinoa). Salt bladders were identified in spinach similar to those in quinoa, an new result in the literature. To detect the bladders in spinach, the spinach varieties Gazelle and Seaside and the quinoa genotype CPAC 09 were used. The bladders were analyzed using optical, confocal, and SEM-EDS microscopy. Genetic evaluations were carried out to identify 19 genes related to salt tolerance in spinach leaves and isolated bladders. Spinach bladders were responsible for the accumulation of Na, Cl, and K and quinoa bladders for the accumulation of K and Cl. This proves the presence of spinach tolerance mechanisms to saline-sodic soils, and we propose the reclassification of this plant from glycophyte to facultative halophyte, similar to quinoa.