Growth inhibition of arable weeds by cerato‐platanin, a plant immune defense activator of fungal origin

BACKGROUND: The herbicide sector needs new modes of action and new ecofriendly molecules as active ingredients. In this study, we investigated the stimulation of the plant immune system as a strategy to reduce weed growth, a mechanism not exploited by any commercial herbicide. Plants possess an innate immune system able to detect pathogens' molecules such as cerato-platanin (CP), a fungal protein elicitor produced by Ceratocystis platani. As sensitivity of arable weeds to microbial elicitors is mostly unknown, the ability of CP to reduce germination and early seedling growth was examined in some Poaceae and Amaranthaceae by using wheat as an off-target species. RESULTS: CP-treated seeds from Lolium multiflorum, Digitaria sanguinalis and Amaranthus hybridus resulted in stunted seedling growth, demonstrating sensitivity to the protein. In contrast, A. palmeri, A. tuberculatus and Avena fatua were unaffected by the treatment. A more detailed characterization of the sensitivity of L. multiflorum showed that CP-specific growth inhibition occurred at concentrations ≥75 μM. Western-blot analysis showed absorption of CP by L. multiflorum seedlings, while RT-qPCR analyses revealed the overexpression of defense genes, such as the pathogenesis-related (PR) gene chitinase 1 and the ethylene-biosynthesis gene ACO1. CP was also effective on Lolium spp. populations resistant to the acetyl-coenzyme A carboxylase (ACCase) inhibitor pinoxaden, while it did not adversely affect germination of Triticum aestivum. CONCLUSION: Besides the classic use as resistance inducers against pests and diseases, we show that plant immune defense activators from microbes may act as selective herbicides with a mode of action so far unexploited. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.