Postdoctoral Associate Donald Danforth Plant Science Center
Disclosure: Disclosure information not submitted.
Quinoa is a very nutritious pseudocereal adapted to the nutrient-poor, saline and water-limited soils of the Andean Altiplano. Because of these properties, there is growing interest in expanding quinoa cultivation, but quinoa incurs great yield losses at high temperatures ( >32°C), limiting its cultivation. We studied the phenotypes, genes, and mechanisms that potentially affect quinoa seed yield at high temperatures. By heating only the roots or shoots of quinoa, yield losses (~75%) were attributed to shoot heating, while root heating did not significantly affect yield. To identify phenotypes leading to yield loss from shoot heating, we used both manual and image-based phenotyping. Seed imaging revealed that yield loss from shoot heating was due to low seed production, with relatively small effects on seed size. Fruit formation was low in plants with heated shoots explaining low seed production. Whole plant images were classified into green or yellow pixels using machine learning in PlantCV, revealing that plants with heated shoots had delayed maturity. Further, plants with heated shoots produced more yield from panicles that escaped heat than control, although this was not sufficient to recover the yield lost from panicles exposed to heat. This suggests that quinoa uses an avoidance strategy to survive heat. Transcriptomic analysis showed that transcription factors differentially expressed in plants with heated shoots and low yield had been previously associated with flower development and flower opening. This led us to examine flower development and flower opening phenotypes. Flower microscopy showed that flowers from plants with heated shoots were less developed. Interestingly, while ~50% control flowers opened during the day, only ~13% flowers from plants with heated shoots opened during the same period. Closed flowers may cause yield loss under heat by limiting pollen dispersal, which is necessary to produce fruit and seed in quinoa’s mostly female flowers.