Prospects for developing durable resistance in populations of forest trees

Sniezko, Richard A.; Liu, Junjun

doi:10.1007/s11056-021-09898-3

Cited by 12 publications

(17 citation statements)

References 52 publications

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“…This is important especially for genetic dissection of plant QR to pathogens. Large genetic diversity with continuous resistance level in plant populations is a key prerequisite for successful selection of future plant generations for durable disease resistance in breeding programs ( Sniezko and Liu, 2022 ).…”

Section: Discussionmentioning

confidence: 99%

“…The current genetic analyses results suggest that a fraction of the composite seed family can be selected in a new breeding cycle to gain higher levels of genetic resistance to Annosus root and butt rot disease. Conventional selection of disease-resistant trees is done by inoculation of progeny, followed by phenotypic assessment, taking many years to complete with high costs for forest tree breeders ( Sniezko and Liu, 2022 ). Advent of novel genomics resources and breeding tools is recognized as a revolutionary force that has changed conventional breeding practices in the last two decades.…”

Section: Discussionmentioning

confidence: 99%

“…Hemlock trees have shallow root systems, making infected trees more susceptible to wind blow and fire damage ( Eis, 1974 ). It appears that planting trees with disease resistance or tolerance is an ideal strategy for management of forest diseases ( Sniezko and Liu, 2022 ). Western hemlock breeding began in the early 1950s with parent tree selection, testing and selection of seed families for establishment of seed orchards ( Jayawickrama, 2003 ; Cappa et al, 2015 ; Cartwright and King, 2021 ).…”

Section: Introductionmentioning

confidence: 99%

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Transcriptomic Reprogramming and Genetic Variations Contribute to Western Hemlock Defense and Resistance Against Annosus Root and Butt Rot Disease

et al. 2022

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Western hemlock (Tsuga heterophylla) is highly susceptible to Annosus root and butt rot disease, caused by Heterobasidion occidentale across its native range in western North America. Understanding molecular mechanisms of tree defense and dissecting genetic components underlying disease resistance will facilitate forest breeding and disease control management. The aim of this study was to profile host transcriptome reprogramming in response to pathogen infection using RNA-seq analysis. Inoculated seedlings were clearly grouped into three types: quantitative resistant (QR), susceptible (Sus), and un-infected (Uif), based on profiles of H. occidentale genes expressed in host tissues. Following de novo assembly of a western hemlock reference transcriptome with more than 33,000 expressed genes, the defensive transcriptome reprogramming was characterized and a set of differentially expressed genes (DEGs) were identified with gene ontology (GO) annotation. The QR seedlings showed controlled and coordinated molecular defenses against biotic stressors with enhanced biosynthesis of terpenoids, cinnamic acids, and other secondary metabolites. The Sus seedlings showed defense responses to abiotic stimuli with a few biological processes enhanced (such as DNA replication and cell wall organization), while others were suppressed (such as killing of cells of other organism). Furthermore, non-synonymous single nucleotide polymorphisms (ns-SNPs) of the defense- and resistance-related genes were characterized with high genetic variability. Both phylogenetic analysis and principal coordinate analysis (PCoA) revealed distinct evolutionary distances among the samples. The QR and Sus seedlings were well separated and grouped into different phylogenetic clades. This study provides initial insight into molecular defense and genetic components of western hemlock resistance against the Annosus root and butt rot disease. Identification of a large number of genes and their DNA variations with annotated functions in plant resistance and defense promotes the development of genomics-based breeding strategies for improved western hemlock resistance to H. occidentale.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Transcriptomic Reprogramming and Genetic Variations Contribute to Western Hemlock Defense and Resistance Against Annosus Root and Butt Rot Disease

et al. 2022

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Section: Introductionmentioning

confidence: 99%

“…The assumption was that a species cannot have any resistance to a pest with which it has not coevolved (28, 29). However, many studies have shown that in many cases native species do marshal heritable defensive responses to non-native invaders (30, 31). Successful breeding programs have produced American beech ( Fagus grandifolia ) resistant to beech bark disease ( Neonectria spp transmitted by Cryptococcus fagisuga ) (32), eastern white pine ( Pinus strobus ) resistant to white pine blister rust ( Cronartium ribicola ) (33) and Port Orford cedar ( Chamaecyparis lawsoniana ) (22) resistant to the root rot pathogen Phytophthora lateralis .…”

Section: Introductionmentioning

confidence: 99%

Profiles of secoiridoids and alkaloids in tissue of susceptible and resistant green ash progeny reveal patterns of induced responses to emerald ash borer inFraxinus pennsylvanica

Stanley

Carey

Mason

et al. 2022

Preprint

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The emerald ash borer (Agrilus planipennis, EAB) invasion in North America threatens most North American Fraxinus species, including green ash (F. pennsylvanica), the mostly widely distributed species. A small number of green ash (lingering ash, 0.1-1%) survive years of heavy EAB attack and kill more EAB larvae when challenged in greenhouse studies than susceptible controls. We combined untargeted metabolomics with intensive phenotyping of segregating F1 progeny from susceptible or lingering ash parents to detect chemotypes associated with defensive responses to EAB. We examined three contrasting groups: low larval kill (0-25% of larvae killed), high larval kill (55-95% of larvae killed) and uninfested. Contrasting the chemotypes of these groups revealed evidence of an induced response to EAB. Infested trees deployed significantly higher levels of select secoiridoids than uninfested trees. Within the infested group, the low larval kill (LLK) individuals deployed significantly higher levels of select secoiridoids than the high larval kill (HLK) individuals. The HLK individuals deployed significantly higher concentrations of three metabolites annotated as aromatic alkaloids compared to the LLK and uninfested individuals. We propose a two-part model for the North American Fraxinus response to EAB wherein every individual has the capacity to detect and respond to EAB, but only certain trees mount an effective defense, killing enough EAB larvae to prevent or minimize lethal damage to the vascular system. Integration of intensive phenotyping of structured populations with metabolomics reveals the multi-faceted nature of the defenses deployed in naive host populations against invasive species.

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Disease resistance in whitebark pine and potential for restoration of a threatened species

Sniezko,

Johnson,

Kegley

et al. 2023

Plants People Planet

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Societal impact statementForests world‐wide are being negatively affected by non‐native, invasive pathogens and pests, and some tree species face uncertain futures. To retain these species as components of future forests, the rare genetic resistance that exists needs to be identified and harnessed. The applied tree improvement program for whitebark pine (Pinus albicaulis), a threatened (in the United States) and endangered (in Canada) keystone species in many forests in western North America, provides an example of what can be accomplished in a relatively short timeframe. The level and frequency of resistance vary by location, and this information will be used to implement the national restoration plan.Summary Forest trees face serious threats from non‐native diseases and pests, often causing high mortality of both the existing trees and regeneration. Developing populations with genetic resistance can help restore forests and retain affected species. Resistance programs have historically focused on species of high economic importance; however, the threats to species of little direct economic value that provide other important ecosystem services are also great. We examined the frequency, level, and geographic variation in genetic resistance to white pine blister rust in the threatened Pinus albicaulis (whitebark pine), a keystone species in high‐elevation ecosystems in western North America. In the two trials reported here, 2‐year‐old seedling progeny of 225 whitebark pine parent trees were inoculated with two geographic sources of the fungal pathogen Cronartium ribicola and evaluated over 5 years for an array of resistance traits. The trials focused primarily on parent trees from the Oregon and Washington populations. We found unexpectedly high levels of quantitative resistance in some seedling families and populations, in stark contrast to levels observed in similar resistance programs with other North American white pine species such as Pinus monticola and Pinus lambertiana. The level of resistance found in some whitebark pine populations provides optimism about potential recovery efforts for this species. Restoration efforts are underway by government agencies, tribes, and non‐government organizations in both the United States and Canada. These efforts may help boost support for applied genetic resistance programs in other forest tree species severely affected by non‐native pathogens or pests.

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Prospects for developing durable resistance in populations of forest trees

Cited by 12 publications

References 52 publications

Transcriptomic Reprogramming and Genetic Variations Contribute to Western Hemlock Defense and Resistance Against Annosus Root and Butt Rot Disease

Transcriptomic Reprogramming and Genetic Variations Contribute to Western Hemlock Defense and Resistance Against Annosus Root and Butt Rot Disease

Profiles of secoiridoids and alkaloids in tissue of susceptible and resistant green ash progeny reveal patterns of induced responses to emerald ash borer inFraxinus pennsylvanica

Disease resistance in whitebark pine and potential for restoration of a threatened species

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