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Quinoa (Chenopodium quinoa Willd.) is a facultative halophyte and some varieties are able to cope with salinity levels as high as those present in sea water. Due to its traditionally broad cultivation area (from the salt flats of the Andes at 3,800 m above sea level to the seacoast and from Colombia down to southern Chile), there is a very wide range of quinoa cultivars adapted to specific conditions displaying a broad genetic variability in stress tolerance. For this reason, quinoa offers a valuable source of germplasm for breeding new cultivars adapted to stressful environments in diverse geographical conditions and for identifying mechanisms potentially useful in breeding tolerant glycophytes. In Chile, the genetic distance between highland (altiplano) and coastal cultivars of quinoa has been assessed but their responses to salinity are less known. In the present work, the response to salt treatments (0, 100 and 300 mM NaCl) was investigated in one altiplano landrace, R49, and two coastal ones, VI-1 and VR (from central and southern Chile, respectively). Salt treatment caused a significant increase in Na+ concentrations in all plant organs; the Na+ concentration accumulated in leaves under 300 mM salt was highest in VI-1 and was ca. 1.5- to 3-fold higher in leaves and roots of plants grown under 300 mM NaCl than 100 mM NaCl. Growth was significantly inhibited by the lower salt concentration only in R49, whereas 300 mM NaCl reduced growth also in VI-1 and VR, albeit to a lower extent than in R49. The concentrations of photosynthetic pigments, total phenolics and flavonoids were differentially affected by salt in leaves of the three cultivars. Seed production at harvest was unaffected or even enhanced (VR) by 100 mM NaCl relative to controls, while with 300 mM it was reduced in R49 and VI-1 (ca. 80% and 40% inhibition, respectively) but was not affected in VR. The germinability of seeds collected from plants grown in the presence (100 or 300 mM) or absence (0 mM) of NaCl was tested on agar plates containing 0-500 mM NaCl. Results showed that the response varied between landraces with VR exhibiting the highest sensitivity (germination was inhibited even by 100 mM NaCl). Seed protein profiles (SDS-PAGE of total proteins and the amount of the 11S seed storage protein chenopodin) were compared among different cultivars not treated with salt and the effect of salt treatments on protein profile were checked in the frame of the single cultivar; this allow to compare the differences due to the genotype and also the plant response to the salt treatments.

Salinity is today one of the most widespread constraints in irrigated agriculture. Thus, salt tolerance is an agronomically important trait receiving increasing attention among scientists worldwide. Quinoa is tolerant to soil salinity and other adverse environmental factors, hence it attracts the attention of researchers as a possible crop in a changing world scenario in which scarcity of water resources and increasing soil and water salinization are the primary causes of crop loss. Quinoa’s exceptional tolerance to salinity, frost, drought and other types of abiotic stress also makes it a model species for investigating cellular, physiological, biomolecular and morphological mechanisms at the basis of stress tolerance in halophytes and in plants as a whole. There are quinoa ecotypes adapted to valley, highland, salt desert, sea level and tropical environments, displaying broad genetic variability in salinity tolerance. For this reason, quinoa represents a valuable resource for selection of the most suitable material and for breeding new varieties adapted to different environmental and geographical conditions. In this chapter, scientific studies on salinity tolerance in quinoa conducted in the last decade by numerous research groups operating in at least nine different countries are described. We focus on studies in which different quinoa genotypes are compared for their response to saline conditions, demonstrating that salt tolerance is a complex, multigenic trait involving a plethora of physiological and structural adaptations. Results available to date regarding the effect of salinity on the nutritional properties of quinoa are reported.

La salinidad está hoy entre las restricciones más extendidas en la agricultura de regadío. Así, la tolerancia a la sal es un rasgo agronómicamente importante que está recibiendo cada vez más atención entre los científicos de todo el mundo. La quinua es tolerante a la salinidad del suelo y otros factores ambientales adversos, y por consiguiente atrae la atención de los investigadores como un cultivo posible en un escenario mundial cambiante en el que la escasez de los recursos hídricos y el aumento de la salinización del suelo y el agua son las principales causas de la pérdida de cultivos. La tolerancia excepcional de la quinua a la salinidad, heladas, sequías y otros tipos de estrés abiótico también hace que sea una especie modelo para la investigación de los mecanismos celulares, fisiológicos, biomoleculares y morfológicas en la base de la tolerancia al estrés en halófitas y en las plantas en su conjunto. Hay ecotipos de quinua adaptadas al valle, altiplano, salares, el nivel del mar y los trópicos, que muestran una amplia variabilidad genética de la tolerancia a la salinidad. Por esta razón, la quinua representa un recurso valioso para la selección del material más adecuado para la obtención de nuevas variedades adaptadas a diferentes condiciones ambientales y geográficas. En este capítulo, se describen los estudios científicos sobre la tolerancia a la salinidad en la quinua realizados en la última década por numerosos grupos de investigación que operan en al menos nueve países diferentes. Nos centramos en los estudios en los que se comparan diferentes genotipos de quinua por su respuesta a condiciones de salinidad, lo que demuestra que la tolerancia a la sal es un rasgo complejo y multigénico que implica una gran cantidad de adaptaciones fisiológicas y estructurales. Se reportan los resultados disponibles hasta ahora sobre el efecto de la salinidad sobre las propiedades nutricionales de la quinua.

Jasmonates (JAs) and spermidine (Sd) influence fruit (and seed) development and ripening. In order to unravel their effects in peach fruit, at molecular level, field applications of methyl jasmonate (MJ) and propyl dihydrojasmonate (PDJ), and Sd were performed at an early developmental stage (late S1). At commercial harvest, JA-treated fruit were less ripe than controls. Realtime RT-PCR analyses confirmed a down-regulation of ethylene biosynthetic, perception and signaling genes, and flesh softening-related genes. The expression of cell wall-related genes, of a sugar-transporter and hormone-related transcript levels was also affected by JAs. Seeds from JA-treated fruit showed a shift in the expression of developmental marker genes suggesting that the developmental program was probably slowed down, in agreement with the contention that JAs divert resources from growth to defense. JAs also affected phenolic content and biosynthetic gene expression in the mesocarp. Levels of hydroxycinnamic acids, as well as those of flavan-3-ols, were enhanced, mainly by MJ, in S2. Transcript levels of phenylpropanoid pathway genes were up-regulated by MJ, in agreement with phenolic content. Sd-treated fruits at harvest showed reduced ethylene production and flesh softening. Sd induced a short-term and long-term response patterns in endogenous polyamines. At ripening the up-regulation of the ethylene biosynthetic genes was dramatically counteracted by Sd, leading to a down-regulation of softening-related genes. Hormone-related gene expression was also altered both in the short- and long-term. Gene expression analyses suggest that Sd interfered with fruit development/ripening by interacting with multiple hormonal pathways and that fruit developmental marker gene expression was shifted ahead in accord with a developmental slowing down. 24-Epibrassinolide was applied to Flaminia peaches under field conditions early (S1) or later (S3) during development. Preliminary results showed that, at harvest, treated fruit tended to be larger and less mature though quality parameters did not change relative to controls.