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Bernays, Elizabeth A.; Oppenheim, Sara J.; Chapman, R. F.; Kwon, Hye-Ok; Gould, Fred

doi:10.1023/a:1005430010314

Cited by 97 publications

(22 citation statements)

References 21 publications

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“…Chlorogenic acid has been shown to act as a chemical defense against invertebrate herbivores (Bernays et al, 2000; Ikonen et al, 2001), though very little is known of how, or if, chlorogenic acid acts as a defense against fungal infections in plants, as Si does.…”

Section: Discussionmentioning

confidence: 99%

Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores

Huitu¹,

Forbes²,

Helander

et al. 2014

Front. Plant Sci.

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Grasses have been considered to primarily employ tolerance in lieu of defense in mitigating damage caused by herbivory. Yet a number of mechanisms have been identified in grasses, which may deter feeding by grazers. These include enhanced silicon uptake, hosting of toxin-producing endophytic fungi and induction of secondary metabolites. While these mechanisms have been individually studied, their synergistic responses to grazing, as well as their effects on grazers, are poorly known. A field experiment was carried out in 5 × 5 m outdoor enclosures to quantify phytochemical changes of either endophyte-infected (E+) or endophyte-free (E-) meadow fescue (Schedonorus pratensis) in response to medium intensity (corresponding with densities of ca. 1200 voles/ha for 5 weeks during 3 months) or heavy intensity (ca. 1200 voles/ha for 8 weeks during 3 months) grazing by a mammalian herbivore, the field vole (Microtus agrestis). A laboratory experiment was then conducted to evaluate the effects of endophyte infection status and grazing history of the grass diet on vole performance. As predicted, grazing increased foliar silicon content, by up to 13%. Grazing also increased foliar levels of phosphorous and several phenolic compounds, most notably those of the flavonols isorhamnetin-diglycoside and rhamnetin derivative. Silicon concentrations were consistently circa 16% higher in E+ grasses than in E-grasses, at all levels of grazing. Similarly, concentrations of chlorogenic acid derivative were found to be consistently higher in E+ than in E- grasses. Female voles maintained on heavily grazed grasses suffered higher mortality rates in the laboratory than female voles fed ungrazed grass, regardless of endophyte infection status. Our results conclusively demonstrate that, in addition to tolerance, grasses employ multi-tiered, effective defenses against mammalian grazers.

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Section: Discussionmentioning

confidence: 99%

Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores

Huitu¹,

Forbes²,

Helander

et al. 2014

Front. Plant Sci.

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“…The results reported here may suggest a more complex relationship between antifeeding effects and the identities and concentrations of secondary compounds likely to be encountered. The generalization is known that generalists are behaviorally less sensitive to deterrent compounds than specialists (Bernays et al 2000). However, our findings could provide new information on the behavioral responses in these two species.…”

Section: Discussionmentioning

confidence: 99%

“…Caterpillars with a restricted host plant range are behaviorally more sensitive to deterrents, bitter plant secondary metabolites, than polyphagous caterpillars (Bernays and Chapman 1987, 1994; Bernays et al 2000; Jermy 1964), although this is not necessarily true in other orders (Eichenseer and Mullin 1997). Most behavioral comparisons are based on phylogenetically closely related species with different host ranges (Bernays and Chapman 1987, 2000; Bernays et al 2000).…”

Section: Introductionmentioning

confidence: 99%

“…Most behavioral comparisons are based on phylogenetically closely related species with different host ranges (Bernays and Chapman 1987, 2000; Bernays et al 2000). A model has been developed that seeks to explain these differences in terms of central nervous system processing rather than differences in sensory input (Schoonhoven and Blom 1988), and there is experimental support for such a model (Bernays and Chapman 2000).…”

Section: Introductionmentioning

confidence: 99%

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Comparisons of Contact Chemoreception and Food Acceptance by Larvae of Polyphagous Helicoverpa armigera and Oligophagous Bombyx mori

et al. 2013

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We compared food choice and the initial response to deterrent treated diet between fifth instars of Helicoverpa armigera, a polyphagous generalist pest, and Bombyx mori, an oligophagous specialist beneficial. Bombyx mori was more behaviorally sensitive to salicin than to caffeine. The relative sensitivities were reversed for H. armigera, which was tolerant to the highest levels of salicin found in natural sources but sensitive to caffeine. A single gustatory receptor neuron (GRN) in the medial styloconic sensillum of B. mori was highly sensitive to salicin and caffeine. The styloconic sensilla of H. armigera did not respond consistently to either of the bitter compounds. Phagostimulants also were tested. Myo-inositol and sucrose were detected specifically by two GRNs located in B. mori lateral styloconic sensillum, whereas, in H. armigera, sucrose was sensed by a GRN in the lateral sensillum, and myo-inositol by a GRN in the medial sensillum. Myo-inositol responsiveness in both species occurred at or below 10−3 mM, which is far below the naturally occurring concentration of 1 mM in plants. Larval responses to specific plant secondary compounds appear to have complex determinants that may include host range, metabolic capacity, and gustatory repertoire.Electronic supplementary materialThe online version of this article (doi:10.1007/s10886-013-0303-2) contains supplementary material, which is available to authorized users.

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“…Endogenous alkaloids produced by grasses include hordenine, a phenylethylamine alkaloid from barley, sorghum, millet, and Phalaris aquatica . Hordenine is deterrent to Heliothis caterpillars (Bernays et al, 2000), grasshoppers (Harley and Thorsteinson, 1967), and ruminants (Marten et al, 1976). Indole alkaloids including gramine and perloline occur in barley, P. aquatic , and Festuca arundinacea (McKenzie, 2012).…”

Section: Get Toxic—chemical Defensementioning

confidence: 99%

Get Tough, Get Toxic, or Get a Bodyguard: Identifying Candidate Traits Conferring Belowground Resistance to Herbivores in Grasses

Moore

Johnson

2017

Front. Plant Sci.

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Grasses (Poaceae) are the fifth-largest plant family by species and their uses for crops, forage, fiber, and fuel make them the most economically important. In grasslands, which broadly-defined cover 40% of the Earth's terrestrial surface outside of Greenland and Antarctica, 40–60% of net primary productivity and 70–98% of invertebrate biomass occurs belowground, providing extensive scope for interactions between roots and rhizosphere invertebrates. Grasses invest 50–70% of fixed carbon into root construction, which suggests roots are high value tissues that should be defended from herbivores, but we know relatively little about such defenses. In this article, we identify candidate grass root defenses, including physical (tough) and chemical (toxic) resistance traits, together with indirect defenses involving recruitment of root herbivores' natural enemies. We draw on relevant literature to establish whether these defenses are present in grasses, and specifically in grass roots, and which herbivores of grasses are affected by these defenses. Physical defenses could include structural macro-molecules such as lignin, cellulose, suberin, and callose in addition to silica and calcium oxalate. Root hairs and rhizosheaths, a structural adaptation unique to grasses, might also play defensive roles. To date, only lignin and silica have been shown to negatively affect root herbivores. In terms of chemical resistance traits, nitrate, oxalic acid, terpenoids, alkaloids, amino acids, cyanogenic glycosides, benzoxazinoids, phenolics, and proteinase inhibitors have the potential to negatively affect grass root herbivores. Several good examples demonstrate the existence of indirect defenses in grass roots, including maize, which can recruit entomopathogenic nematodes (EPNs) via emission of (E)-β-caryophyllene, and similar defenses are likely to be common. In producing this review, we aimed to equip researchers with candidate root defenses for further research.

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Cited by 97 publications

References 21 publications

Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores

Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores

Comparisons of Contact Chemoreception and Food Acceptance by Larvae of Polyphagous Helicoverpa armigera and Oligophagous Bombyx mori

Get Tough, Get Toxic, or Get a Bodyguard: Identifying Candidate Traits Conferring Belowground Resistance to Herbivores in Grasses

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