Optimizing drought stress simulation to enhance greenhouse-to-field transferability in barley breeding

Drought stress is a major constraint to barley production under changing climate conditions. A key challenge in drought research is transferring results from controlled greenhouse experiments to natural field environments, as greenhouse trials often only partially capture the environmental complexity relevant for genotype selection. Presumably, adjusting watering regimes multiple times during plant development may improve the predictive value of greenhouse experiments and support more reliable early-generation selection for drought resilience.To test this hypothesis, sixteen diverse barley genotypes, including wild barley introgression lines and elite cultivars, were evaluated under eight watering treatments using a high-throughput, automated phenotyping platform. The treatments differed in terms of watering intensity and timing. Alternating watering treatments, mimicking natural conditions, promoted tillering but reduced ear fertility, harvest index, and yield, compared to constant stress or well-watered conditions. However, in general, the correlations between the alternating watering treatments and field data were higher than those between constant stress conditions and field data. The highest comparability with field drought data was observed for a treatment that alternated weekly between watering and drought phases, although this depended on the target environment.Overall, the design of the watering regime strongly influences the reliability of greenhouse drought simulations. Several genotypes demonstrated stable yields across drought scenarios and field conditions, suggesting drought resilience. Therefore, optimized drought treatments are essential for improving the transferability of results from the greenhouse to the field, enabling the early selection of advanced genotypes that can adapt to changing precipitation patterns in agriculture.