An official website of the United States government
The emerald ash borer (EAB), Agrilus planipennis, is a destructive invasive insect of North American ash (Fraxinus). While microorganisms associated with the beetle may contribute to tree decline and death, the microbial community succession during an EAB attack is unknown. We repeatedly sampled the bottom two meters of green ash (Fraxinus pennsylvanica) and black ash (Fraxinus nigra) in seven stands across an infestation gradient over four years. Amplicon libraries were sequenced from control phloem tissue of trees showing no symptoms of infestation, uninfested phloem of trees with EAB, infested phloem (galleries), frass, and larvae to determine if there are shifts in the fungal and bacterial communities as trees succumb to EAB attack. We found that the control phloem communities significantly differed from the beetle-infested phloem in both tree species. Furthermore, as EAB progressed in its attack from the top limbs to the tree’s base, the microbial communities in uninfested phloem outside the galleries shifted away from communities in phloem of control trees. In infested phloem, more than 80% of the detected taxa were absent from control trees (i.e., most taxa were non-latent). However, the relative abundance of latent taxa in infested phloem was higher than the relative abundance of the non-latent taxa, especially for potential canker-causing fungi, which increased 21-fold and 32-fold in black ash and green ash trees, respectively. These findings provide valuable insight into how a woodboring beetle shapes the microbial environment within trees over time, influencing the overall microbial diversity, such as canker-causing and wood decay taxa.
more »
« less
This content will become publicly available on August 1, 2026
The Role of Phenylpropanoids and the Plant Microbiome in Defences of Ash Trees Against Invasive Emerald Ash Borer
ABSTRACT Plants have coevolved with herbivorous insects for millions of years, resulting in variation in resistance both within and between species. Using a manipulative experiment combined with untargeted metabolomics, microbiome sequencing and transcriptomics approaches, we investigated the roles of plant metabolites and the microbiome in defence mechanisms in native resistant Manchurian ash (Fraxinus mandshurica) trees and non‐native susceptible velvet ash (Fraxinus velutina) trees against the highly invasive emerald ash borer (EAB,Agrilus planipennis). Comparative transcriptomics and metabolomics analyses show that the phenylpropanoid pathway, which is enriched in differentially expressed genes and differentially abundant metabolites, may serve as a potential regulator of resistance. Additionally, the microbiome is distinctly shifted in two ash species. Indicator taxa analysis reveals that the distinct genera are dominant in the galleries of two ash species, for example,Pseudomonasin velvet, andHafnia‐Obesumbacteriumin Manchurian. The strong correlation between indicator taxa and metabolites suggests that the chemical compounds might impact the microbial community in phloem directly or indirectly, or vice versa. This study significantly enhances our understanding of the variation in resistance between ash species and its contribution to the invasion success of EAB, providing valuable insights for the development of pest management strategies.
more »
« less
- Award ID(s):
- 2030036
- PAR ID:
- 10655281
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Plant, Cell & Environment
- Volume:
- 48
- Issue:
- 8
- ISSN:
- 0140-7791
- Page Range / eLocation ID:
- 5680 to 5698
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Midwestern forests are currently impacted by two prominent invaders, the emerald ash borer (EAB; Agrilus planipennis) and Amur honeysuckle (AHS; Lonicera maackii). The loss of ash (Fraxinus spp.) trees due to EAB invasion can further facilitate AHS invasion, driving changes in the composition of forest leaf litter to reflect a greater portion of labile, more easily decomposed litter. To evaluate the extent to which these changes alter ecosystem function, we conducted litter bag and culture-based decomposition experiments using leaf litter from sugar maple (Acer saccharum), oak (Quercus spp.), black ash (Fraxinus nigra), green ash (Fraxinus pennsylvanica), spicebush (Lindera benzoin) and AHS. To further understand the mechanism driving differences in decay rates, we inoculated six species of decomposing fungi separately onto both single species and multispecies (half AHS and half native species) leaf litter and measured decomposition rate, fungal growth and enzymatic activity in laboratory-based cultures. AHS leaf litter decomposed faster, had increased fungal growth, and had higher activity for carbon degrading enzymes compared to native species leaf litter. Furthermore, multispecies mixtures followed the same patterns as AHS, suggesting that the addition of AHS to leaf litter to native litter will accelerate ecosystem functions related to carbon breakdown. Consequently, forests that experience the invasion of AHS and EAB induced loss of ash are likely to have faster rates of decomposition, potentially resulting in an influx of available nutrients.more » « less
-
Abstract Invasive forest pests can affect the composition and physical structure of forest canopies that may facilitate invasion by non‐native plants. However, it remains unclear whether this process is generalizable across invasive plant species at broad spatial scales, and how other landscape characteristics may simultaneously facilitate non‐native plant invasion. Here, we assembled a dataset of over 3000 repeatedly measured forest plots and quantified the impact of emerald ash borer (EAB,Agrilus planipennis) residence time, land cover, and forest structure on the accumulation and coverage of invasive plants. We show plots in counties with longer EAB residences tended to accumulate more invasive plants than plots with shorter EAB residences. On average, nearly half of the plots with ash (Fraxinusspp.) in counties with EAB accumulated an additional 0.48 invasive plant species over the 5‐ to 6‐year resample interval compared to plots with ash in counties without EAB at the time of sampling. Increases in invasive species coverage were also evident in counties with EAB—although residence time did not have a strong effect, while forest gap fraction and vertical complexity were each negatively associated with increased coverage. This work has implications for understanding how invasive forest pests can facilitate the spread of non‐native plants.more » « less
-
Abstract Forester and logger responses to the invasive emerald ash borer (EAB) could substantially affect regions across the United States. We analyzed forester and logger responses to EAB in Massachusetts and Vermont, exploring characteristics associated with purposeful targeting of substantial ash properties; managing forests differently because of EAB; and regeneration goals. One-third of respondents increased timber sales on ash properties, motivated by ecological, not economic, impacts of EAB. Nearly 60% said EAB changed their management activity in stands with ash; changes influenced by the ecological impact of EAB and not economic factors. Those influenced by EAB’s ecological impact to choose properties with substantial ash were more likely to have increased harvest area size, sawtimber removal, and harvest intensity. Loggers were more likely than foresters to remove small-diameter ash and low-grade trees. Both rated regenerating economically valuable species well adapted to the site as their highest essential priority.more » « less
-
Abstract With populations of threatened and endangered species declining worldwide, efforts are being made to generate high quality genomic records of these species before they are lost forever. Here, we demonstrate that data from single Oxford Nanopore Technologies (ONT) MinION flow cells can, even in the absence of highly accurate short DNA-read polishing, produce high quality de novo plant genome assemblies adequate for downstream analyses, such as synteny and ploidy evaluations, paleodemographic analyses, and phylogenomics. This study focuses on three North American ash tree species in the genusFraxinus(Oleaceae) that were recently added to the International Union for Conservation of Nature (IUCN) Red List as critically endangered. Our results support a hexaploidy event at the base of the Oleaceae as well as a subsequent whole genome duplication shared bySyringa,Osmanthus,Olea, and Fraxinus. Finally, we demonstrate the use of ONT long-read sequencing data to reveal patterns in demographic history.more » « less
