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Detection method for Fusarium torreyae the canker pathogen of the critically endangered Florida torreya, Torreya taxifolia
Abstract
Florida torreya (Torreya taxifolia Arn.) is an endangered conifer with a very limited range in the USA: two counties in Florida and one in Georgia, along the Apalachicola River. The species was once abundant in its small native range but suffered a major decline, ~99% loss, in the late 1950s to early 1960s that is thought to have been caused by a disease. Recently, a canker disease caused by Fusarium torreyae was identified as the primary cause of Florida torreya decline. Efforts to restore and preserve the species in situ and ex situ are hampered by lack of pathogen‐free planting stock, and there exists an interest in methods to verify pathogen presence in seeds and seedlings prior to collection and transport for planting. This paper presents a new species‐specific diagnostic method that enables detection of F. torreyae and may allow for conservation programmes to ensure germplasm is free of the pathogen prior to planting.
... If not done carefully, augmentation and reintroduction may generate unintended impacts on recipient forests, such inadvertently introduced pathogens or invasive species (Dreaden et al., 2020). To minimize impacts, augmentation and reintroduction activities can prioritize forests or other habitats that are already prone to human activities, such as in many community and private forest areas. ...
Worldwide, thousands of orchid species are harvested from the wild. Widespread legal and illegal unsustainable
trade has contributed to the decline of many species. However, there is also evidence of long-term, sustainable
wild harvest of some orchid species that contribute to local livelihoods and cultural traditions. There is a clear
need to help guide harvesters and resource managers towards sustainability. However, there is currently no
appropriate framework to guide local harvest decisions, which is especially problematic given huge data limitations,
variations in on-the-ground capacity to monitor and manage resources, and considering that the potential
for sustainable harvest is context-specific. We reviewed the literature on orchid harvest, ecology and
demography; assessed information on the life history of 27 harvested species; and drew on our experience with
diverse orchid taxa to identify characteristics expected to influence harvest sustainability. We identified 23
characteristics within four themes: abundance and distribution; species traits related to growth and reproduction;
local management practices; and demand. We selected 12 characteristics for which information was available for
many species and observable in the field, and used an iterative process to develop a decision-making dichotomous
key. The key identifies if and how the harvest of a given population at a given time can be conducted more
sustainably, offering sets of considerations that harvesters and managers can use and adapt to local contexts.
Critical research gaps include techniques for partial plant harvest and for augmentation; and investigation into
A phytochemical investigation on the MeOH extract of the leaves and twigs of the endangered conifer Torreya jackii Chun led to the isolation and characterization of 21 structurally diverse diterpenoids. Among them, six are previously undescribed, including four abietane-type (torreyins A−D, resp.) and two labdane-type diterpenoids (torreyins E and F). Their structures and absolute configurations were determined by a combination of spectroscopic methods, calculated/experimental electronic circular dichroism (ECD) data, and single-crystal X-ray diffraction analyses. In particular, torreyins A−C are rare 11,12-seco-abietane type diterpenoids possessing a dilactone moiety, and their biosynthetic pathway starting from a co-occurring abietane derivative (i.e., cyrtophyllone B) was briefly proposed. Among the isolates, 7-oxo-dehydroabietic acid and 15-methoxy-7,13-abietadien-18-oic acid showed considerable inhibitory effects against acetyl-coenzyme A carboxylase 1 (ACC1) and protein tyrosine phosphatase 1 B (PTP1B), with IC50 values of 3.1 and 6.8 μM, respectively.
As one of the world's most threatened coniferous trees, Torreya taxifolia has attracted the attention of a variety of conservation organizations and researchers across its native country of the USA and beyond. The current status of the species is one of very poor individual health with trees being very short and failing to produce seeds, while being confined to a restricted range in the south-eastern US. The status reflects a precipitous decline that is widely reported to be influenced by a number of threats including over-exploitation primarily for construction materials, modifications to natural systems and most notably, a pathogenic fungus which results in the poor growth and lack of reproduction and has been named Fusarium torreyae. However, the species is a glacial relict at the southernmost extent of its post-glacial range and as such, is also likely to suffer from the impacts of climate change. Current conservation actions include attempts to carefully monitor individual trees and document the impacts of catastrophes such as Hurricane Michael in 2018 and ‘cage’ them to prevent damage from deer; comprehensive collections of cuttings and seed to be grown in botanic gardens, and a range of translocation attempts to either bolster the species in its native range, or identify new sites in which it might thrive.
Canker disease of prickly ash (Zanthoxylum bungeanum) has caused a decline in the production of this economically important spice in northern China in the past 25 y. To identify the etiological agent, 38 fungal isolates were recovered from symptomatic tissues from trees in five provinces in China. These isolates were identified by conducting BLASTN queries of NCBI GenBank and phylogenetic analyses of DNA sequence data from the nuclear ribosomal internal transcribed spacer region (ITS rDNA), a portion of the translation elongation factor 1-α (TEF1) gene, and genes encoding RNA polymerase II largest (RPB1) and second largest (RPB2) subunits. Results of these analyses suggested that 30/38 isolates belonged to two novel fusaria most closely related to the Florida torreya (Torreya taxifoliaArn.) pathogen,Fusarium torreyaein Florida and Georgia. These three canker-inducing tree pathogens form a novel clade withinFusariumhere designated theF. torreyaespecies complex (FTOSC). BLASTN queries of GenBank also revealed that 5/38 isolates recovered from cankers represented an undescribed phylogenetic species within theF. solanispecies complex (FSSC) designated FSSC 6. Stem inoculations of three fusaria onZ. bungeanumresulted in consistent canker symptoms from which these three fusaria were recovered. The two novel fusaria, however, induced significantly larger lesions than FSSC 6. Herein, the two novel prickly ash pathogens are formally described asF. zanthoxyliandF. continuum.
A canker disease of Florida torreya (Torreya taxifolia) has been implicated in the decline of this critically endangered species in its native ranee of northern Florida and southeastern Georgia. In surveys of eight Florida torreya sites, cankers were present on all dead trees and 71 to 100% of living trees, suggesting that a fungal pathogen might be the causal agent. To identify the causal agent, nuclear ribosomal internal transcribed spacer region (ITS rDNA) sequences were determined for 115 fungi isolated from cankers on 46 symptomatic trees sampled at three sites in northern Florida. BLASTn searches of the GenBank nucleotide database, using the ITS rDNA sequences as the query, indicated that a novel Fusarium species designated Fsp-1 might be the etiological agent. Molecular phylogenetic analyses of partial translation elongation factor I-alpha (EF-1) and RNA polymerase second largest subunit (RPB2) gene sequences indicate that Fsp-1 represents a novel species representing one of the earliest divergences within the Gibberella clade of Fusarium. Results of pathogenicity experiments established that the four isolates of Fsp-1 tested could induce canker symptoms on cultivated Florida torreya in a growth chamber. Koch's postulates were completed by the recovery and identification of Fsp-1 from cankers of the inoculated plants.
Laurel wilt, caused by the fungus Raffaelea lauricola, is an exotic disease that affects members of the Lauraceae plant family in the southeastern United States. The disease is spreading rapidly in native forests and is now found in commercial avocado groves in south Flor- ida, where an accurate diagnostic method would improve disease man- agement. A polymerase chain reaction (PCR) method based on ampli- fying the ribosomal small-subunit DNA, with a detection limit of 0.0001 ng, was found to be suitable for some quantitative PCR applica- tions; however, it was not taxon specific. Genomic sequencing of R. lauricola was used to identify and develop primers to amplify two taxon-specific simple-sequence repeat (SSR) loci, which did not am- plify from related taxa or host DNA. The new SSR loci PCR assay has a detection limit of 0.1 ng of R. lauricola DNA, is compatible with traditional and real-time PCR, was tested in four labs to confirm con- sistency, and reduces diagnostic time from 1 week to 1 day. Our work illustrates pitfalls to designing taxon-specific assays for new pathogens and that undescribed fungi can limit specificity.
During a survey for pathogens of Florida torreya (Torreya taxifolia) conducted in 2009, a novel Fusarium species was isolated from cankers affecting this critically endangered conifer whose current range is restricted to northern Florida and southwestern Georgia. Published multilocus molecular phylogenetic analyses indicated that this pathogen represented a genealogically exclusive, phylogenetically distinct species representing one of the earliest divergences within the Gibberella clade of Fusarium. Furthermore, completion of Koch's postulates established that this novel species was the causal agent of Florida torreya canker disease. Here, we formally describe this pathogen as a new species, Fusarium torreyae. Pure cultures of this species produced long and slender multiseptate sporodochial conidia that showed morphological convergence with two distantly related fusaria, reflecting the homoplasious nature of Fusarium conidial morphology.
Torreyataxifolia Arn. is an endangered conifer restricted to ravine slopes along the Apalachicola River in northern Florida. The species began a decline in the 1950s that has resulted in fewer than 1500 trees remaining extant in the wild. Allelic variation was examined for 189 trees throughout its range. The species is characterized by low overall levels of genetic variation: seven of 20 loci were variable; each polymorphic locus had no more than two alleles; mean heterozygosity (He) was 0.064. Over 78% of this measured genetic variation was found within populations; no spatial pattern was detected in the remaining variation between populations within drainage regions, across drainage regions, or across soil types. This genetic information was used to plan tissue collection for a permanent offsite population.
Torreya taxifolia is a coniferous tree that is endemic to the 35 km stretch of bluffs and ravines along the east side of the Apalachicola River in northern Florida and adjacent southern Georgia. This formerly locally abundant tree declined during the 1950s and 1960s as a result of disease and is currently on the US Endangered Species list. For sparsely distributed species it can often be difficult to determine both current and historic population sizes. Historical descriptions of the distribution (203 km2) and relative abundance (14.2% of dominant ravine trees) of T. taxifolia are used along with current measures of forest structure to estimate the pre-decline population density (30 trees/ha) and size (∼0.3–0.65 million individuals). Survey information from five extant stands is used to estimate current population size (∼500–4000 individuals). The surveys were conducted in areas with known high tree densities such that a simple extrapolation to the entire distribution would produce a gross over-estimate of population size. We therefore use a variety of assumptions to produce a range of estimates for total population sizes. Regardless of the particular model, our estimates suggest that T. taxifolia has lost at least 98.5% of its total population size since the early 1900s. We discuss these results in relation to the potential difficulties likely of restoring sustainable populations of this species.
Host range and biology of Fusarium Torreyae (Sp. Nov), causal agent of canker disease of Florida Torreya Torreya taxifolia Arn
- A J Trulock
Trulock, A. J. (2013). Host range and biology of Fusarium Torreyae (Sp.
Nov), causal agent of canker disease of Florida Torreya Torreya taxifolia
Arn.). Thesis-University of Florida, Gainesville, FL USA.