Mechanical stress priming to enhance crop resilience

Exposure to mechanical stress alters the growth and development of plants, and can prime them to be resistant to subsequent environmental stress. The application of mechanical stress therefore has the potential to improve the resilience of crop plants to the effects of climate change. The principle of priming plants has been common in cereal farming in Japan for centuries, where farmers apply repeated mechanical treatment to seedlings to induce beneficial traits. We mimicked this practice in the laboratory, using a robot to pull a heavy roller across the surface of soil and pressing plants in a controlled manner. The effect of timing and frequency of mechanical stimulation was assessed using the model species Arabidopsis thaliana. Expression of touch-response marker genes XTH22, WRKY40 and CML24 was found to be significantly altered by application of mechanical stress at different times of day. Transcriptome analysis indicated that plants become less responsive to mechanical stimulus following repeated exposure, with accommodation of gene regulation observed for many core touch-response pathways. To assess the potential of mechanical stress priming for agriculture, repeated rolling treatment was applied to the African orphan crop Eragrostis tef (tef), which is extremely prone to lodging. Mechanical treatment was found to significantly delay lodging and improve root anchorage of tef plants. In addition to laboratory-based work, I interviewed cereal farmers across the UK to assess farmers’ attitudes to mechanical stress priming. Such practices, particularly the application of a single post-emergence rolling treatment, were found to be widespread across the UK, and considered by many farmers to be traditional knowledge. This investigation demonstrated the value of farmers’ knowledge, and the need for this to be better recognised and integrated within formal knowledge systems. In preliminary trials, mechanical rolling of heritage and modern wheat varieties was shown to increase the number or tillers and crown roots per plant, broadly in line with farmers’ perceptions on the effect of rolling in the field. Overall, the results of this interdisciplinary study suggest great potential for mechanical stress priming to improve cereal crop resilience in a wide range of contexts.