the Choreography of Drought Tolerance in Barley

Barley is the fourth most important cereal crop worldwide and Germany is the third largest barley-producing country. Despite the outstanding environmental adaptability of barley, which outcompetes any other cereal crop, future yield improvement is hampered by biotic and abiotic stresses. In Germany, barley yields showed a strong fluctuation during the last 15 years, reflecting the impact of climate change. One factor is the increased frequency of drought events, especially in spring during the vegetative growth phase. Understanding the genetics of biomass formation under well-watered and seasonal drought conditions can provide a basis for stabilizing and increasing grain yield. In our studies, a pot based imaging system was used to evaluate daily biomass assessed in a diverse reference collection of barley developed from the IPK genebank. The experimental setup comprised a drought period of 18 days with watering regime corresponding to 20% field capacity (well-watered: 90%) and a 14 day long recovery period. Drought treatment started in the tillering phase and experiments ended around tipping time. We obtained high heritability for biomass under both conditions over the whole observation period, which made this trait amenable for genome-wide association scans (GWAS). GWAS were performed for each day independently within the well-watered and within the drought stress treatments. Different genetic loci were identified for early and later vegetative biomass. Similarly, specific loci were identified for biomass under well-watered and stress conditions. Results point at candidate genes involved in plant growth hormone regulation and phenology. Although plants were quickly recovering upon the end of drought, the results demonstrate a strong effect of drought on grain yield. In addition, we observed a positive correlation of vegetative biomass to grain yield, which might blaze a trail to further increase yield potential.