Metabolomic approaches suggests two mechanisms of drought response post anthesis in Mediterranean oat (Avena sativa L.) cultivars

Oats ( Avena sativa L) is a temperate cereal and important healthy cereal cultivated for food and feed. Therefore understanding drought resposes in oats will have a significant impact on oat production under harsh climatic conditions. In particular, drought during anthesis (flowering) will affect grain filling, quality and yield. Here we characterised metabolite responses of two Mediterranean oat ( Avena sativa L.) cultivars Flega and Patones during drought stress at anthesis. In the more drought tolerant Patones, the developing grains from the top (older) and bottom (younger) spikelets of primary panicle were found to be larger in size in response to drought, suggesting accelerated grain development. Flega showed a more rapid transition to flowering and grain development under drought. Metabolomes of source (sheath, flag leaf, rachis) and sink (developing grains) tissues from Patones showed differential accumulation in fatty acids levels, including α-linolenic acid, sugars and amino acids with drought. Flega showed enhanced energy metabolism in both source and sink tissues. Lower levels of glutathione in source tissues and the accumulation of ophthalmic acid in the grains of Flega were indicators of oxidative stress. From our study, we observed two metabolite regulation in these two cultivars during drought at anthesis. In one, α-linolenic acid-linked events could accelerate grain filling whilst in other oxidative stress could influence traits such as flowering time. Overall this work provide first insight into the metabolite wide regulation in source and sink tissues during anthesis oats under drought stress.