Abstract
American chestnut (Castanea dentata Borkh.) was a dominant tree species in its native range in eastern North America until the accidentally introduced fungus Cryphonectria parasitica (Murr.) Barr, that causes chestnut blight, led to a collapse of the species. Different approaches (e.g., genetic engineering or conventional breeding) are being used to fight against chestnut blight and to reintroduce the species with resistant planting stock. Because of large climatic differences within the distribution area of American chestnut, successful reintroduction of the species requires knowledge and consideration of local adaptation to the prevailing environmental conditions. Previous studies revealed clear patterns of genetic diversity along the northeast-southwest axis of the Appalachian Mountains, but less is known about the distribution of potentially adaptive genetic variation within the distribution area of this species. In this study, we investigated neutral and potentially adaptive genetic variation in nine American chestnut populations collected from sites with different environmental conditions. In total, 272 individuals were genotyped with 24 microsatellite (i.e., simple sequence repeat (SSR)) markers (seven genomic SSRs and 17 EST-SSRs). An FST-outlier analysis revealed five outlier loci. The same loci, as well as five additional ones, were significantly associated with environmental variables of the population sites in an environmental association analysis. Four of these loci are of particular interest, since they were significant in both methods, and they were associated with environmental variation, but not with geographic variation. Hence, these loci might be involved in (temperature-related) adaptive processes in American chestnut. This work aims to help understanding the genetic basis of adaptation in C. dentata, and therefore the selection of suitable provenances for further breeding efforts.
Document Type
Article
Publication Date
11-9-2018
Digital Object Identifier (DOI)
https://doi.org/10.3390/f9110695
Funding Information
This research was partly funded by The American Chestnut Foundation.
Related Content
The following are available online at https://www.mdpi.com/1999-4907/9/11/695/s1, Data file S1: Genotypic data, Figure S1: Plots of delta K and log likelihood for each K based on the complete marker set (a), and potentially neutral markers that did not show deviations from neutrality in the outlier analysis (b), Figure S2: Clustering of individuals for K = 3 based on potentially neutral markers, Table S1: Environmental variables of the analyzed populations, Table S2: Primer information, Table S3: FIS values of the SSR markers in the different populations, Table S4: Percentage of SSR pairs with significant linkage disequilibrium, p < 0.05, Table S5: Frequency of null alleles, Table S6: SSR-markers significantly associated with principal components within the two different population clusters (a) Ontario, Maryland, Kentucky, Asheville, and Murphy; (b) Massachusetts, New York, and Portland, Table S7: BLAST results and linkage groups of the loci significantly associated with the environmental variables.
Repository Citation
Müller, Markus; Nelson, Charles Dana; and Gailing, Oliver, "Analysis of Environment-Marker Associations in American Chestnut" (2018). Forest Health Research and Education Center Faculty Publications. 4.
https://uknowledge.uky.edu/fhrec_facpub/4
Supplementary Materials
Notes/Citation Information
Published in Forests, v. 9, issue 11, 695, p. 1-15.
© 2018 by the authors. Licensee MDPI, Basel, Switzerland.
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).