Tillering plasticity of drought-stressed barley genotypes under different re-watering regimes

One future challenge of agriculture will be maintaining food security in times of climate change. Future plant breeding, therefore, has to account for the genotypes’ survival during drought and a good recovery ability after rainfall events. We aimed at investigating the re-tillering behavior of selected barley genotypes (cultivars and wild barley introgression lines) in different drought and re-watering scenarios, which were applied in a high-throughput phenotyping facility. Re-tillering describes the activation of additional tillers after post-stress irrigation. Twenty-three selected genotypes of the barley NAM population HEB-25, along with three control genotypes, were evaluated in four replicates under five distinct treatment conditions. In this experiment, re-tillering was particularly pronounced in an alternating watering and stress treatment, where the resumption of irrigation post-stress enabled full recovery of the plants. However, it was noted that while re-watering after a stress period promotes tiller activation and the development of fertile ears, it also tends to increase the number of sterile ears. The degree of sterile ear formation varied significantly among different genotypes, highlighting the critical role of genetic factors in modulating plant responses to re-tillering and post-stress irrigation. It is important to note that excessive re-tillering has been shown to exhibit a negative correlation with fertile ear weight. The impact of focusing on tiller number and re-tillering behavior in future barley breeding may be significant, particularly in the context of climate change. By selecting for genotypes with appropriate tillering plasticity, breeders can develop barley varieties that are more resilient to stress conditions such as drought.