From roots to shoots: the hidden impact of weeds on crops

Weeds can hurt crops by changing how they grow and develop, not just by taking resources, according to a new study that focused on the impact of weed signals on maize roots, which revealed that weeds have a much earlier and negative effect than previously thought. The study, carried out by David Horvath and colleagues and published in AoB PLANTS, has identified specific genes and proteins that help to explain how weeds affect crop growth.

Multiple studies have shown that crops such as maize are particularly vulnerable to the impact of weeds during the first weeks of growth when stress response pathways are activated in response to the presence of weeds. However, these studies have mainly focused on the response of above-ground plant parts, neglecting the potential impact of weeds on belowground processes.

To address this knowledge gap, researchers designed a system to expose maize to belowground signals from weeds, investigating the impact on the maize root transcriptome during this critical early period of growth. The results were striking, with gene set enrichment analyses revealing the over-representation of genes associated with oxidative stress signalling, nitrogen use and transport, and defence responses.

The study also revealed the role of specific proteins involved in ABA signalling as important for initiating maize’s early response to weeds. ABA is a plant hormone that plays a role in stress responses, so this finding suggests that weeds may be triggering a stress response in maize.

Interestingly, the study also identified the over-representation of specific promoter sequences that can be bound by proteins involved in cold or drought response, biotic and abiotic defence and light-regulated gene expression.

Overall, this research indicates that weeds have a much earlier and more complex impact on crop growth and development than previously understood. By altering crop processes long before they directly compete for resources, weeds may be setting up a competitive advantage that persists even after removal. Understanding how weeds impact crop growth and development is crucial for developing effective weed management strategies that can protect crop yields and ensure food security.

“The tight time course in this study provided the opportunity to identify early signaling processes involved in the detection and response of maize to weeds. Additionally…this is the first study focused on the response of maize root tissue specifically to belowground weed-generated signals.”

Horvath et al, 2023

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Horvath, D.P. Doherty C.J., Desai J., Clark N., Anderson J.V., Chao W.S. (2023) “Weed-induced changes in the maize root transcriptome reveal transcription factors and physiological processes impacted early in crop-weed interactions” AoB PLANTS. Available at: https://doi.org/10.1093/aobpla/plad013