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Plant-mediated interactions between two belowground agricultural pests uncovered: When field mustard plants are infected by root-knot nematodes, they change their defence strategy in a way that unintentionally benefits another belowground herbivore: the cabbage root fly. This is the conclusion of a new study led by IGZ researchers published in Plant Physiology (March 2025 issue). A combination of bioassays and ecometabolomic analyses, the researchers found that root-knot nematodes alter the plant's chemical defences, affecting its natural resistance to subsequent attackers.
Axel Touw, Jessil Pajar, Nicole van Dam and colleagues found that nearly 1.5 times more adult cabbage root flies (Delia radicum) emerged from field mustard (Brassica rapa) plants infected with root-knot nematodes (Meloidogyne incognita) than uninfected plants. Although the nematodes and flies do not interact physically, the outcomes of the study imply that they can indirectly influence one another via the plant on which they feed. This effect is linked to the plant’s chemical defence, specifically to the induced production of specific classes of glucosinolates, sulphur-rich compounds characteristic of crucifers. Nematode-infected plants showed increased production of indole glucosinolates, while levels of aliphatic glucosinolates — compounds known to hamper root fly development — dropped by 10 to 25 %. The researchers suggest that antagonistic crosstalk between the biosynthetic pathways of these compounds may explain the shift.
“Our study shows that complex interactions between belowground herbivores can significantly alter plant chemistry,” says Dr Axel Touw. “Such indirect effects could intensify or mitigate pest damage in crops, which makes them highly relevant for sustainable agriculture – particularly in integrated pest management strategies.”
The results prove that plant-mediated interactions between soil-dwelling organisms are more influential than previously thought. Because root knot nematodes are highly abundant in soils, they are often among the first organisms to interact with the plant. Such interactions, which modify the plant’s chemical defences, can affect the natural resistance of the plant to future attackers, including pest insects such as the cabbage root fly. These insights could inform more effective strategies for pest management, especially in agroecosystems with multiple root feeders.
Leibniz Institute of Vegetable and Ornamental Crops
The Leibniz Institute of Vegetable and Ornamental Crops (IGZ) is a research institute of the Leibniz Association and contributes to solving current global challenges with science-based findings from basic and applied research in horticulture. These include the preservation of biodiversity, combating climate change and the still widespread malnutrition. The institute is jointly funded by the Ministry of Science, Research and Culture of the State of Brandenburg (MWFK) and the Federal Ministry of Food and Agriculture (BMEL). The IGZ is based in Großbeeren.
Dr Axel J. Touw | Postdoctoral Researcher Plant Biotic Interactions| Email touw@igzev.de |hone +49 (0) 33 701 7 825
https://doi.org/10.1093/plphys/kiaf109 Axel J Touw, Nhu Tran, Andreas Schedl, Jessil A Pajar, Cong Van Doan, Henriette Uthe, Nicole M van Dam, Root-knot nematode infection enhances the performance of a specialist root herbivore via plant-mediated interactions, Plant Physiology, 2025.
A Fuchsine-stained root-knot containing a juvenile nematode observed in the fine roots of infected f ...
Axel J. Touw
IGZ
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