Restoring a keystone tree species for the future: American chestnut assisted migration plantings in an adaptive silviculture experiment

Clark, Peter W.; Freeman, Alissa J.; D’Amato, Anthony W.; Schaberg, Paul G.; Hawley, Gary J.; Evans, Kevin; Woodall, Christopher W.

doi:10.1016/j.foreco.2022.120505

Cited by 12 publications

(3 citation statements)

References 64 publications

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“…While the concept of assisted migration does not exactly fit the case of American chestnut—a species for which there are no natural populations to migrate—it can nevertheless provide a framework in which to think about the differential targeting of locally adapted restoration populations to future geography and climate ( 58 ). For example, chestnuts planted northward outside of the historical range may suffer winter injury, but exhibit increased combined growth and survival ordinal scores than most other assisted migration tree species from the eastern United States (red spruce, northern red oak, eastern hemlock, black cherry, bigtooth aspen, black birch, and bitternut hickory) ( 59 ). Germplasm from the central and northern seed zones (SZ.2 and SZ.1, respectively), exhibit less winter injury and should be considered for use in the most northern replanting locations ( 13 ).…”

Section: Discussionmentioning

confidence: 99%

A genome-guided strategy for climate resilience in American chestnut restoration populations

Sandercock,

Westbrook,

Zhang

et al. 2024

Proc. Natl. Acad. Sci. U.S.A.

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American chestnut ( Castanea dentata ) is a deciduous tree species of eastern North America that was decimated by the introduction of the chestnut blight fungus ( Cryphonectria parasitica ) in the early 20th century. Although millions of American chestnuts survive as root collar sprouts, these trees rarely reproduce. Thus, the species is considered functionally extinct. American chestnuts with improved blight resistance have been developed through interspecific hybridization followed by conspecific backcrossing, and by genetic engineering. Incorporating adaptive genomic diversity into these backcross families and transgenic lines is important for restoring the species across broad climatic gradients. To develop sampling recommendations for ex situ conservation of wild adaptive genetic variation, we coupled whole-genome resequencing of 384 stump sprouts with genotype–environment association analyses and found that the species range can be subdivided into three seed zones characterized by relatively homogeneous adaptive allele frequencies. We estimated that 21 to 29 trees per seed zone will need to be conserved to capture most extant adaptive diversity. We also resequenced the genomes of 269 backcross trees to understand the extent to which the breeding program has already captured wild adaptive diversity, and to estimate optimal reintroduction sites for specific families on the basis of their adaptive portfolio and future climate projections. Taken together, these results inform the development of an ex situ germplasm conservation and breeding plan to target blight-resistant breeding populations to specific environments and provides a blueprint for developing restoration plans for other imperiled tree species.

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Section: Discussionmentioning

confidence: 99%

A genome-guided strategy for climate resilience in American chestnut restoration populations

Sandercock,

Westbrook,

Zhang

et al. 2024

Proc. Natl. Acad. Sci. U.S.A.

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“…As such, assisted migration will be necessary for maladapted regions (Aitken et al, 2008). Chestnuts planted northward outside of the parent range will suffer winter injury, but perform better than other assisted migration species from the eastern United States (Clark et al, 2022). Germplasm from the central and northern seed zones (Seed Zones 2 and 1), exhibits less winter injury and should be considered for use in the most northern replanting locations (Schaberg et al, 2022).…”

Section: Matching Adaptive Portfolios To Future Climatesmentioning

confidence: 99%

The road to restoration: Identifying and conserving the adaptive legacy of American chestnut

Sandercock

Westbrook

Zhang

et al. 2023

Preprint

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The American chestnut (Castanea dentata) is a functionally extinct tree species that was decimated by an invasive fungal pathogen in the early 20thcentury. Disease resistant chestnuts have been developed through hybridization and genetic modification, but these populations may lack the adaptive genomic diversity necessary to restore the species across its climatically diverse historical range. An understanding of the genomic architecture of local adaptation in wild American chestnut and identification of seed zones for germplasm conservation are necessary in order to deploy locally adapted, disease-resistant American chestnut populations. Here, we characterize the genomic basis of climate adaptation in remnant wild American chestnut, define seed zones based on climate envelopes and adaptive diversity, and make sampling recommendations for germplasm conservation. Whole genome re-sequencing of 384 trees coupled with genotype-environment association methods suggest the species range can be most parsimoniously subdivided into three seed zones characterized by relatively homogeneous allele frequencies relative to rangewide adaptive diversity. Using these data, we developed a method to estimate the number of samples required from each seed zone to recapitulate standing adaptive diversity in each seed zone, and found that on average, 21-29 trees will need to be conserved to capture 95% of the wild adaptive diversity. Taken together, these results will inform the development of anex situgermplasm conservation and breeding plan to develop locally adapted blight-resistant American chestnut populations, and provide a blueprint for developing restoration plans for other imperiled tree species.

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“…Climate models predict that this region will undergo temperature increase, heat wave events and extreme drought [ 16 ]. Studies on the impact of climate change on chestnut, including tolerance, adaptation and genetic variability, have increased considerably in recent years [ 17 , 18 , 19 , 20 , 21 ]. Because this species developed in contrasting climate conditions, different evolutionary pressures acted on its genome, giving rise to ecotypes adapted to different climates [ 18 , 22 , 23 , 24 ].…”

Section: Introductionmentioning

confidence: 99%

Warming Scenarios and Phytophthora cinnamomi Infection in Chestnut (Castanea sativa Mill.)

Dorado

Gallego

Chaves

et al. 2023

Plants

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The main threats to chestnut in Europe are climate change and emerging pathogens. Although many works have separately addressed the impacts on chestnut of elevated temperatures and Phytophthora cinnamomi Rands (Pc) infection, none have studied their combined effect. The objectives of this work were to describe the physiology, secondary metabolism and survival of 6-month-old C. sativa seedlings after plants were exposed to ambient temperature, high ambient temperature and heat wave events, and subsequent infection by Pc. Ten days after the warming scenarios, the biochemistry of plant leaves and roots was quantified and the recovery effect assessed. Plant growth and root biomass under high ambient temperature were significantly higher than in plants under ambient temperature and heat wave event. Seven secondary metabolite compounds in leaves and three in roots were altered significantly with temperature. Phenolic compounds typically decreased in response to increased temperature, whereas ellagic acid in roots was significantly more abundant in plants exposed to ambient and high ambient temperature than in plants subjected to heat waves. At recovery, leaf procyanidin and catechin remained downregulated in plants exposed to high ambient temperature. Mortality by Pc was fastest and highest in plants exposed to ambient temperature and lowest in plants under high ambient temperature. Changes in the secondary metabolite profile of plants in response to Pc were dependent on the warming scenarios plants were exposed to, with five compounds in leaves and three in roots showing a significant ‘warming scenario’ × ‘Pc’ interaction. The group of trees that best survived Pc infection was characterised by increased quercetin 3-O-glucuronide, 3-feruloylquinic acid, gallic acid ethyl ester and ellagic acid. To the best of our knowledge, this is the first study addressing the combined effects of global warming and Pc infection in chestnut.

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Restoring a keystone tree species for the future: American chestnut assisted migration plantings in an adaptive silviculture experiment

Cited by 12 publications

References 64 publications

A genome-guided strategy for climate resilience in American chestnut restoration populations

A genome-guided strategy for climate resilience in American chestnut restoration populations

The road to restoration: Identifying and conserving the adaptive legacy of American chestnut

Warming Scenarios and Phytophthora cinnamomi Infection in Chestnut (Castanea sativa Mill.)

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