Kicking a plant whilst it’s down – caterpillar herbivory on nematode infested plants

Does the impact of above-ground herbivory on root-knot nematode-induced responses depend on the
nematode’s life cycle stage?

Root-knot nematodes (RKN) are plant parasites that damage the roots of the host plant. RKN infection impairs movement of water and minerals from roots to shoots, which can limit plant productivity and fitness. While the roots are being infested by nematodes belowground, plant leaves aboveground can be attacked by herbivorous insects, such as caterpillars. The loss of leaf material due to caterpillar feeding can also adversely impact plant productivity. Together the damage caused by RKN and herbivorous insects can reduce crop production by 20 %. Pesticides can be used to control these pests however, whilst often effective, these can have negative impacts on human and environmental health. Efforts to identify natural plant resistance traits for these pests and interaction between RKN and caterpillars may help us to develop sustainable pest management strategies.

Caterpillar (Spodoptera exigua) leaf feeding decreases jasmonic acid signaling in tomato plants whose roots are infected by root-knot nematode (Meloidogyne incognita) when the nematode is at the reproduction stage (boxed). Image credit: Mbaluto et al.

In their new study published in AoBP, Mbaluto et al. investigated how caterpillars (Spodoptera exigua) might affect root defence responses triggered by RKN (Meloidogyne incognita) infection at different stages of the RKN life cycle. They demonstrated that caterpillar feeding on the nematode infected plants decreases jasmonic acid signalling when the nematode is at reproductive stage. These results generate a better understanding of the molecular and chemical mechanisms underlying frequent nematode–plant–caterpillar interactions in natural and agricultural ecosystems. The authors suggest that testing the impact of long periods of aboveground herbivory on nematode-induced root responses are needed to reveal how the interactions with belowground responses might change over longer interaction times.

Researcher highlight

Crispus Mbaluto is a doctoral researcher in the Molecular Interaction Ecology research group at the German Centre for Integrative Biodiversity Research (iDiv), Leipzig, Germany. His main research interest is to understand the mechanisms that drive interactions between belowground and aboveground insects/pests via shared host plant. In particular, he studies whether parasitic root nematodes affect the level of tomato plants resistance to shoot feeding insect herbivores, i.e., caterpillars and aphids. Crispus’ work involves experimental manipulations in the glasshouse and laboratory and the use of innovative approaches that span the fields of molecular biology, chemical ecology, metabolomics, and transcriptomics. His overall aspiration in research is to advance knowledge on plant-mediated interactions and use it to help tomato growers manage pests in a more sustainable manner. This can help to reduce reliance on pesticides, boosting the economy as well as biodiversity.

William Salter

William (Tam) Salter is a Postdoctoral Research Fellow in the School of Life and Environmental Sciences and Sydney Institute of Agriculture at the University of Sydney. He has a bachelor degree in Ecological Science (Hons) from the University of Edinburgh and a PhD in plant ecophysiology from the University of Sydney. Tam is interested in the identification and elucidation of plant traits that could be useful for ecosystem resilience and future food security under global environmental change. He is also very interested in effective scientific communication.

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