Variation in antioxidant capacity of quinoa (Chenopodium quinoa Will) subjected to drought stress

Phytochemicals which are found in fruit and vegetables have synergistic effects, responsible for their antioxidant activity that can scavenge harmful free radicals. Environmental stress factors during plant growth can regulate the accumulation of phytochemicals and other functional substances in seeds or other organs. The economic value that these bioactive substances have acquired, make it necessary to study the cropping systems affect high nutritional and functional values of food. The purpose of this research was to determine the effect of controlled water restriction on antioxidant content in seeds of three genotypes of quinoa (Chenopodium guinea Willd.) and its effect on the potential yield. The study was conducted in the south-central zone of Chile (Chillan, 36 degrees 35 ' 43,2 '' S, 72 degrees 04 ' 39,9 '' W and 140 m elevation), under field conditions and under controlled conditions in a greenhouse, during the 2010-2011 season. In both experiments, a randomized complete block experimental design with a split-plot arrangement was used. Main plot treatment was available water level (AW), once 50% of the grains were in the grain filling stage, establishing four irrigation treatments in which water applied was supplying when soil water content achieved 95%, 60%, 40%, and 20% AW. The subplots included three quinoa genotypes. Seed yield, the antioxidant characteristics of quinoa seeds using DPPH and CUPRAC method, the total phenolic compound and vitamin E were evaluated. Results indicated an increase of the antioxidant capacity in seeds of plants exposed to greater water restriction (20% AW), detecting a mean of 6.1 and 2.9 mg gallic acid equivalent (GAE)g(-1) under controlled and field condition, respectively. Values of vitamin E did not differ between treatment of available water and genotype. Seed yield potential was reduced in different magnitude among genotype. It was concluded that the antioxidant capacity of quinoa seeds increases by applying 20% available water when seeds are between milk and dough phenological stage, without a considerably reduction on seed yield in genotype AG 2010. (C) 2013 Elsevier B.V. All rights reserved.