Root-exuded benzoxazinoids can alleviate negative plant-soil feedbacks

The chemical language of plant-microbe-microbe associations: an introduction to a Virtual Issue

This Editorial introduces the Virtual Issue ‘Chemical language of plant–microbe–microbe associations’ that includes the following papers: Basak et al. (2024), Böttner et al. (2023), Brisson et al. (2023), Feng et al. (2023), Gfeller et al. (2024), Gómez‐Pérez et al. (2023), Hong et al. (2022, 2023), Hu et al. (2024), Jiang et al. (2024), Lee et al. (2024), Nakano (2024), Ökmen et al. (2023), Revillini et al. (2023), Rovenich & Thomma (2023), Simonin et al. (2022), Snelders et al. (2023), Walsh et al. (2024), Wen et al. (2023), Xia et al. (2023), Xie et al. (2023), Zhang et al. (2023, 2024), Zheng et al. (2023), Zhou et al. (2023, 2024). Access the Virtual Issue at www.newphytologist.com/virtualissues.

Understanding the chemical language mediating maize immunity and environmental adaptation

Diverse networks of specialized metabolites promote plant fitness by mediating beneficial and antagonistic environmental interactions. In maize (Zea mays), constitutive and dynamically formed cocktails of terpenoids, benzoxazinoids, oxylipins, and phenylpropanoids contribute to plant defense and ecological adaptation. Recent research has highlighted the multifunctional nature of many specialized metabolites, serving not only as elaborate chemical defenses that safeguard against biotic and abiotic stress but also as regulators in adaptive developmental processes and microbiome interactions. Great strides have also been made in identifying the modular pathway networks that drive maize chemical diversity. Translating this knowledge into strategies for enhancing stress resilience traits has the potential to address climate-driven yield losses in one of the world's major food, feed, and bioenergy crops.

Associational Effects of Desmodium Intercropping on Maize Resistance and Secondary Metabolism

Intercropping is drawing increasing attention as a strategy to increase crop yields and manage pest pressure, however the mechanisms of associational resistance in diversified cropping systems remain controversial. We conducted a controlled experiment to assess the impact of co-planting with silverleaf Desmodium (Desmodium uncinatum) on maize secondary metabolism and resistance to herbivory by the spotted stemborer (Chilo partellus). Maize plants were grown either in the same pot with a Desmodium plant or adjacent to it in a separate pot. Our findings indicate that co-planting with Desmodium influences maize secondary metabolism and herbivore resistance through both above and below-ground mechanisms. Maize growing in the same pot with a Desmodium neighbor was less attractive for oviposition by spotted stemborer adults. However, maize exposed only to above-ground Desmodium cues generally showed increased susceptibility to spotted stemborer herbivory (through both increased oviposition and larval consumption). VOC emissions and tissue secondary metabolite titers were also altered in maize plants exposed to Desmodium cues, with stronger effects being observed when maize and Desmodium shared the same pot. Specifically, benzoxazinoids were strongly suppressed in maize roots by direct contact with a Desmodium neighbor while headspace emissions of short-chain aldehydes and alkylbenzenes were increased. These results imply that direct root contact or soil-borne cues play an important role in mediating associational effects on plant resistance in this system.

Neighbour-induced changes in root exudation patterns of buckwheat results in altered root architecture of redroot pigweed

Roots are crucial in plant adaptation through the exudation of various compounds which are influenced and modified by environmental factors. Buckwheat root exudate and root system response to neighbouring plants (buckwheat or redroot pigweed) and how these exudates affect redroot pigweed was investigated. Characterising root exudates in plant-plant interactions presents challenges, therefore a split-root system which enabled the application of differential treatments to parts of a single root system and non-destructive sampling was developed. Non-targeted metabolome profiling revealed that neighbour presence and identity induces systemic changes. Buckwheat and redroot pigweed neighbour presence upregulated 64 and 46 metabolites, respectively, with an overlap of only 7 metabolites. Root morphology analysis showed that, while the presence of redroot pigweed decreased the number of root tips in buckwheat, buckwheat decreased total root length and volume, surface area, number of root tips, and forks of redroot pigweed. Treatment with exudates (from the roots of buckwheat and redroot pigweed closely interacting) on redroot pigweed decreased the total root length and number of forks of redroot pigweed seedlings when compared to controls. These findings provide understanding of how plants modify their root exudate composition in the presence of neighbours and how this impacts each other's root systems.

Getting to the root of divergent outcomes in the modulation of plant-soil feedbacks by benzoxazinoids

This article is a Commentary on Gfeller et al. (2024), 241: 2575–2588.