Journal of Fungi (2022) 8 (9 - 969)

Catalina Posada-Vergara, Katharina Lohaus, Mohammad Alhussein, Stefan Vidal and Michael Rostás (2022)
Root colonization by fungal entomopathogen systemically primes belowground plant defense against cabbage root fly
Journal of Fungi 8 (9 - 969)
Abstract: Entomopathogenic fungi infect insects via spores but also live inside plant tissues as endophytes. Frequently, colonization by entomopathogens provides plants with increased resistance against insects, but the mechanisms are little understood. This study investigated direct, local, and systemic root-mediated interactions between isolates of the fungus Metarhizium brunneum and larvae of the cabbage root fly (CRF) Delia radicum attacking Brassica napus plants. All fungal isolates infected CRF when conidia were present in the soil, leading to 43–93% mortality. Locally, root-associated M. brunneum isolates reduced herbivore damage by 10–20% and in three out of five isolates caused significant insect mortality due to plant-mediated and/or direct effects. A split-root experiment with isolate Gd12 also demonstrated systemic plant resistance with significantly reduced root collar damage by CRF. LC-MS analyses showed that fungal root colonization did not induce changes in phytohormones, while herbivory increased jasmonic acid (JA) and glucosinolate concentrations. Proteinase inhibitor gene expression was also increased. Fungal colonization, however, primed herbivore-induced JA and the expression of the JA-responsive plant defensin 1.2 (PDF1.2) gene. We conclude that root-associated M. brunneum benefits plant health through multiple mechanisms, such as the direct infection of insects, as well as the local and systemic priming of the JA pathway.
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Database assignments for author(s): Stefan Vidal, Michael Rostas

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
resistance/tolerance/defence of host
Research topic(s) for beneficials or antagonists:
application technology

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Delia radicum	Brassica - other species	Germany
Metarhizium brunneum (entomopathogen)	Delia radicum	Brassica - other species	Germany