Root-associated entomopathogenic fungi manipulate host plants to attract herbivorous insects

Abstract

Root-associated entomopathogenic fungi (R-AEF) indirectly influence herbivorous insect performance. However, host plant-R-AEF interactions and R-AEF as biological control agents have been studied independently and without much attention to the potential synergy between these functional traits. In this study, we evaluated behavioral responses of cabbage root flies [Delia radicum L. (Diptera: Anthomyiidae)] to a host plant (white cabbage cabbage Brassica oleracea var. capitata f. alba cv. Castello L.) with and without the R-AEF Metarhizium brunneum (Petch). We performed experiments on leaf reflectance, phytohormonal composition and host plant location behavior (behavioral processes that contribute to locating and selecting an adequate host plant in the environment). Compared to control host plants, R-AEF inoculation caused, on one hand, a decrease in reflectance of host plant leaves in the near-infrared portion of the radiometric spectrum and, on the other, an increase in the production of jasmonic, (+)-7-iso-jasmonoyl-l-isoleucine and salicylic acid in certain parts of the host plant. Under both greenhouse and field settings, landing and oviposition by cabbage root fly females were positively affected by R-AEF inoculation of host plants. The fungal-induced change in leaf reflectance may have altered visual cues used by the cabbage root flies in their host plant selection. This is the first study providing evidence for the hypothesis that R-AEF manipulate the suitability of their host plant to attract herbivorous insects.

Root-Associated Entomopathogenic Fungi Modulate Their Host Plant’s Photosystem II Photochemistry and Response to Herbivorous Insects

“…The species M. brunneum is less characterized for its effects on herbivory, but recently, has been shown to induce resistance against pests and pathogens [ 78 ]. Furthermore, isolate KVL 16–36 has been shown to alter the plant phenotype [ 79 ]. Both fungal isolates are obtained from commercial biocontrol products, which make them available for use in plant production systems in several countries.…”

Behavior Matters—Future Need for Insect Studies on Odor-Mediated Host Plant Recognition with the Aim of Making Use of Allelochemicals for Plant Protection

“…The fungal-induced change in leaf reflectance may have altered visual cues used by the cabbage root flies in their host plant selection. This provides first evidence for the hypothesis that R-AEF manipulate the suitability of their host plant to attract herbivorous insects …”

“…Another case study showed sensory integration in the cabbage root fly Delia radicum (Diptera: Anthomyiidae) during the host location and in the interaction with a root-associated entomopathogenic fungi (R-AEF) . It is known that R-AEF indirectly influence herbivorous insect performance .…”

Model Application of Entomopathogenic Fungi as Alternatives to Chemical Pesticides: Prospects, Challenges, and Insights for Next-Generation Sustainable Agriculture

“…For studies related to endophyte-induced secondary compounds, phytohormones, and enzymes, several molecular analyses are commonly being used. The most common technologies used include liquid chromatography-mass spectrometry (LC-MS-MS; Wang et al, 2020 ), gas chromatography-mass spectrometry (GC-MS/MS; Elbanhawy et al, 2019 ), high pressure liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS; Cotes et al, 2020 ), nuclear magnetic resonance spectroscopy (NMR), headspace solid-phase microextraction (HS-SPME), Fourier transform infrared spectroscopy (FTIR), and proteomics ( Al-Ani et al, 2021 ).…”

“…Fungal endophytes are believed to serve as bodyguards for their host plants against primary herbivore pests (Vidal and Jaber, 2015;Jaber and Ownley, 2018). Under moderate to high levels of herbivore attack, plants colonized with endophytic fungi can generally outperform endophyte-free plants (Clay, 1997).…”