Genotype-dependent responses to long-term water stress reveal different water-saving strategies in Chenopodium quinoa Willd.

Abstract

Within the current climate context, freshwater resources have become scarce. Agriculture, especially in rain-fed conditions, should deal with the need of increasing yields to contribute to food security under limiting water availability. Exploring underutilized crops such as Chenopodium quinoa (quinoa) has become a unique opportunity as some of these crops possess the ability to tolerate several abiotic stresses, including drought. In line with this, this work aimed at evaluating the genotype-dependent response to drought by comparing the performance of different European-adapted cultivars (F14, F15, F16, and Titicaca). The results show that the cultivars here evaluated presented different mechanisms to cope with long-term water stress, including changes in phenology, morphology, or physiology. Among them, the cultivar F16 might be the most promising genotype to grow under water-limiting conditions as it presented a reduced foliar total surface (fewer branches and leaves) with higher chlorophyll contents and was able to increase Water Use Efficiency (WUE), reducing the stomatal conductance and keeping CO 2 assimilation rates similar to well-watered conditions. These characteristics lead to F16 maintaining seed yield and increasing harvest index (HI) under water deficit conditions, making it a cultivar tolerant to drought. Furthermore, based on these results, we propose a model in which differences between a water-use efficient and a drought-sensitive genotype are presented. Altogether, we believe that this work will significantly contribute to broadening our understanding of how quinoa responds to long-term water stress highlighting genotype-related differences that will allow the selection of the best-adapted genotypes for water-limiting environments. • Water deficit alters quinoa phenology in a genotype-dependent way accelerating flowering and shortening seed filling stage. • Morphological changes like the reduction of total leaf surface under drought contributes to a reduced water loss in quinoa. • Increments in leaf chlorophyll contents under drought can lead to higher photosynthetic rates. • Chlorophyll fluorescence parameters are developmental stage-dependent but are not sensitive to long-term water deficit. • A reduced water loss and photosynthesis maintenance under water deficit contribute to keep yields in tolerant cultivars.