Graduate Thesis Or Dissertation
 

Genetic Characterization and Bioclimatic Modeling of the Three Varieties of Leptographium wageneri (Cause of Black Stain Root Disease) in the Western USA

Público Deposited

Conteúdo disponível para baixar

Baixar PDF
https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/pk02ck091

Descriptions

Attribute NameValues
Creator
Abstract
  • Black stain root disease (BSRD) is a vascular wilt disease of conifers caused by three varieties of the native, insect-vectored fungal pathogen, Leptographium wageneri (L. wageneri var. wageneri, L. wageneri var. ponderosum, and L. wageneri var. pseudotsugae). Although morphological, physiological, and ecological characteristics differ among the three varieties of L. wageneri, definitive DNA-based validation of pathogen identification has not been previously conducted for isolates of three L. wageneri varieties collected across the western USA. Although BSRD pathogens and hosts are adapted to widely ranging climatic conditions, bioclimatic models have not been previously developed to predict suitable climate space (potential distribution) of BSRD pathogens under contemporary and projected future climates. The objectives of this study are to 1) genetically characterize and define phylogenetic relationships of three varieties of L. wageneri collected from the western USA using DNA-based methods, and 2) predict suitable climate space (potential distribution) of L. wageneri and its three varieties under contemporary and future climate scenarios using bioclimate modeling. BSRD samples were collected directly from black to dark brown streaks in the outer xylem of large roots and/or lower stems of symptomatic conifer trees (Pinus monophylla, P. ponderosa, P. jeffreyi, and/or Pseudotsuga menziesii) in Oregon and California where BSRD was previously reported. GPS points and host data (species, DBH, health status, etc.) were also recorded for each BSRD sample. Wood samples were sterilized for fungal isolation and fungal isolates were grown on selective media, with hyphal tips subsequently transferred to obtain pure cultures. DNA was extracted from pure cultures of 39 L. wageneri isolates and PCR was conducted to amplify 10 loci (28S large subunit ribosomal, actin, β-tubulin, calmodulin, translation elongation factor 1-alpha, mating-type gene 1-1-3, RNA polymerase II subunit, glyceraldehyde-3-phosphate dehydrogenase, and chitin synthase) for DNA sequencing. Phylogenetic analyses were performed using maximum likelihood and Bayesian inference in three parts: 1) individual locus, 2) a combination of two or three loci, 3) concatenated multi-loci sequences, and 4) a combination of two loci with six outgroups. The results demonstrate well-supported separation of all three L. wageneri varieties in multi-loci phylogenies (two-, three-, seven- and/or 10-loci). Previously, the three L. wageneri varieties were described as separate varieties instead of separate species, largely because genetic resources were lacking to distinguish among the three taxa. Phylogenetic results from this study provide solid genetic evidence that three L. wageneri varieties should be elevated to species status, especially when considered in conjunction with previously established differences in morphological, physiological, and ecological characteristics. GPS points were used to obtain the location occurrences of DNA sequence-confirmed varieties of L. wageneri [L. wageneri var. wageneri (N=10), L. wageneri var. ponderosum (N=10), and L. wageneri var. pseudotsugae (N=38)] to predict suitable climate space (potential distribution) under contemporary and projected future climate scenarios using Maximum Entropy (MaxEnt). Four bioclimatic models were run [L. wageneri model (all varieties), L. wageneri var. wageneri, L. wageneri var. ponderosum, and L. wageneri var. pseudotsugae] using 19 bioclimate variables at 30 seconds (~1 km2) spatial resolution from WorldClim. The resulting AUC values for the four MaxEnt bioclimatic models of L. wageneri ranged from 0.88-0.97 under the contemporary climate, which indicate reliable predictions. For bioclimatic models of each L. wageneri variety, the predictions of suitable climate space were compared between 1) contemporary and projected future climates, and 2) contemporary climate and current host distributions. Such comparisons between predictions of potential distribution for host and pathogen provide insights into geographic regions where the BSRD is predicted to potentially occur under contemporary and future climate scenarios. This information will guide land managers as to which areas are currently, or may become, prone to BSRD pathogens so that less susceptible forest species can be planted, selected for, or regenerated across diverse forest sites in the western USA.
License
Resource Type
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Committee Member
Academic Affiliation
Declaração de direitos
Publisher
Peer Reviewed
Language

Relações

Parents:

This work has no parents.

Em Collection:

Itens

Miniatura Título Data de carga Acesso Ações
file details ChoiDaram2023.pdf 2023-04-11 Público Baixar