Light Limitation Impacts Growth but Not Constitutive or Jasmonate Induced Defenses Relevant to Emerald Ash Borer ( Agril
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Light Limitation Impacts Growth but Not Constitutive or Jasmonate Induced Defenses Relevant to Emerald Ash Borer (Agrilus planipennis) in White Fringetree (Chionanthus virginicus) or Black Ash (Fraxinus nigra) Michael S. Friedman 1
&
Chad M. Rigsby 2
&
Don Cipollini 1
Received: 21 July 2020 / Revised: 22 September 2020 / Accepted: 6 October 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract White fringetree is a host for the invasive emerald ash borer (EAB) but is of lower quality than the related and highly susceptible black ash. Field observations suggest that host trees grown in full sun are more resistant to EAB than those in shade, however the impact of light limitation on chemical defenses has not been assessed. We quantified constitutive and jasmonate-induced phloem defenses and growth patterns of white fringetree and black ash under differential light conditions and related them to EAB larval performance. White fringetree had significantly lower constitutive and induced activities of peroxidase, polyphenol oxidase, βglucosidase, chitinase and lignin content, but significantly higher gallic acid equivalent soluble phenolic, soluble sugar, and oleuropein concentrations compared to black ash. Multivariate analyses based on tissue chemical attributes displayed clear separation of species and induced defense responses. Further, EAB performed significantly worse on white fringetree than black ash, consistent with previous studies. Light limitation did not impact measured defenses or EAB larval performance, but it did decrease current year growth and increase photosynthetic efficiency. Overall our results suggest that phenolic profiles, metabolite abundance, and growth traits are important in mediating white fringetree resistance to EAB, and that short-term light limitation does not influence phloem chemistry or larval success. Keywords Invasive pest . Tree defense . Shade . Phenolics . Emerald ash borer . White fringetree
Introduction Plants defend themselves against herbivores by producing a diversity of secondary metabolites and proteins that can reduce digestibility, serve as toxins, or cause oxidative stress to consumers (Fürstenberg-Hägg et al. 2013; War et al. 2012). Light, the main driver of carbon allocation for plants via photosynthesis, is an essential abiotic resource necessary for plant growth and defense production. Low light environments (shade) may constrain the synthesis of some defenses by limiting carbon acquisition (e.g. Calder et al. 2011; Yang et al.
* Michael S. Friedman [email protected] 1
Wright State University, 3640 Colonel Glenn Hwy, Dayton, OH 45435, USA
2
The Bartlett Tree Research Laboratories and The Morton Arboretum, 4100 IL-53, Lisle, IL 60532, USA
2008), which may lead to increased herbivory (Raffa et al. 1998; Suárez-Vidal et al. 2017). This relationship has been explained by the carbon-nutrient balance hypothesis which posits that in low light environments, where carbon is limited, plants should allocate resources to growth rathe
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