Journal articles: 'Kauri Dieback'

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Hood, Ian. "Kauri dieback." Plant Pathology 70, no. 4 (April 4, 2021): 764–66. http://dx.doi.org/10.1111/ppa.13356.

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Waipara, N. W., J. Craw, A. Davis, J. Meys, B. Sheeran, A. Peart, S. Hill, et al. "Management of kauri dieback." New Zealand Plant Protection 62 (August 1, 2009): 407. http://dx.doi.org/10.30843/nzpp.2009.62.4854.

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Kauri illthrift commonly known as Kauri dieback has been identified as an increasing problem affecting kauri (Agathis australis) across the Auckland region A water and soilborne pathogen Phytophthora taxon Agathis (PTA) has been identified as a causal agent of Kauri dieback at some locations particularly within the Waitakeres Ranges Regional Park and Great Barrier Island PTA is associated with a collar rot causing large bleeding basal lesions yellowing foliage and tree death A range of other causal agents including Phytophthora cinnamomi and environmental stress factors were also associated with symptoms at many sites In 2008 Auckland Regional Council implemented a range of standard operational procedures to manage the disease across the region Surveillance surveys are underway to assess overall tree health as well as the potential distribution of PTA in Aucklands kauri forests Survey sites were prioritised in areas with high conservation value iconic trees or high levels of soil disturbance such as tracks intersecting kauri root zones Risk management of the suspected primary vectors of the PTA including people and feral pigs is underway

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Waipara, N. W., S. Hill, L. M. W. Hill, E. G. Hough, and I. J. Horner. "Surveillance methods to determine tree health distribution of kauri dieback disease and associated pathogens." New Zealand Plant Protection 66 (January 8, 2013): 235–41. http://dx.doi.org/10.30843/nzpp.2013.66.5671.

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Kauri dieback is a pest issue that is increasingly affecting kauri forests A water and soilborne pathogen Phytophthora taxon Agathis (PTA) has been identified as a causal agent of kauri dieback at multiple locations particularly within Auckland and Northland In 2008 a passive surveillance and adaptive management programme was initiated to manage the disease across the natural range of kauri Surveys were initially undertaken to determine the distribution and rate of spread of kauri dieback on private land in the Auckland region Methods to evaluate and monitor overall tree health disease symptoms and other potential contributing factors were developed Diagnostic sampling was undertaken to isolate and identify pathogens associated with kauri dieback Along with PTA other Phytophthora species and environmental stress were frequently associated with symptoms at over 400 properties inspected Further management is now required to develop control tools and mitigate further spread

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Hill, Lee, Edward Ashby, Nick Waipara, Robin Taua-Gordon, Aleesha Gordon, Fredrik Hjelm, Stanley E. Bellgard, Emma Bodley, and Linley K. Jesson. "Cross-Cultural Leadership Enables Collaborative Approaches to Management of Kauri Dieback in Aotearoa New Zealand." Forests 12, no. 12 (November 30, 2021): 1671. http://dx.doi.org/10.3390/f12121671.

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In Aotearoa/New Zealand, the soilborne pathogen Phytophthora agathidicida threatens the survival of the iconic kauri, and the ecosystem it supports. In 2011, a surveillance project to identify areas of kauri dieback caused by Phytophthora agathidicida within the Waitākere Ranges Regional Park (WRRP) highlighted the potential impact of the pathogen. A repeat of the surveillance in 2015/16 identified that approximately a quarter of the kauri area within the Regional Park was infected or possibly infected, an increase from previous surveys. The surveillance program mapped 344 distinct kauri areas and showed that 33.4% of the total kauri areas were affected or potentially affected by kauri dieback and over half (58.3%) of the substantial kauri areas (above 5 ha in size) were showing symptoms of kauri dieback. Proximity analysis showed 71% of kauri dieback zones to be within 50 m of the track network. Spatial analysis showed significantly higher proportions of disease presence along the track network compared to randomly generated theoretical track networks. Results suggest that human interaction is assisting the transfer of Phytophthora agathidicida within the area. The surveillance helped trigger the declaration of a cultural ban (rāhui) on recreational access. Te Kawerau ā Maki, the iwi of the area, placed a rāhui over the kauri forest eco-system of the Waitākere Forest (Te Wao Nui o Tiriwa) in December 2017. The purpose of the rāhui was to help prevent the anthropogenic spread of kauri dieback, to provide time for investment to be made into a degraded forest infrastructure and for research to be undertaken, and to help protect and support forest health (a concept encapsulated by the term mauri). Managing the spread and impact of the pathogen remains an urgent priority for this foundation species in the face of increasing pressures for recreational access. Complimentary quantitative and qualitative research programs into track utilization and ecologically sensitive design, collection of whakapapa seed from healthy and dying trees, and remedial phosphite treatments are part of the cross-cultural and community-enabled biosecurity initiatives to Kia Toitu He Kauri “Keep Kauri Standing”.

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Jamieson, A., I. E. Bassett, L. M. W. Hill, S. Hill, A. Davis, N. W. Waipara, E. G. Hough, and I. J. Horner. "Aerial surveillance to detect kauri dieback in New Zealand." New Zealand Plant Protection 67 (January 8, 2014): 60–65. http://dx.doi.org/10.30843/nzpp.2014.67.5723.

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The causal agent of kauri dieback Phytophthora taxon Agathis (PTA) poses a significant threat to kauri (Agathis australis) in northern New Zealand Groundbased field surveys have previously confirmed PTA presence at several locations across Auckland and Northland However ground surveys are limited to areas adjacent to tracks because of difficulty and cost associated with offtrack access in steep terrain along with concern about furthering spread of PTA A methodology for aerial photographic surveillance of kauri dieback was developed and implemented in Wait257;kere Ranges Hunua Ranges and adjacent forest areas Using recently developed GPS technology photographs were embedded with position data so unhealthy trees were easily located later for groundtruthing Aerial survey was found to be a time and costeffective method for surveying large inaccessible areas of forest for kauri dieback The methodology would also be applicable for detection of visible disease or damage symptoms in other canopy tree species

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Horgan, D. B. "The uptake of phosphorus acid sprays into kauri foliage." New Zealand Plant Protection 70 (July 31, 2017): 326. http://dx.doi.org/10.30843/nzpp.2017.70.96.

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Kauri dieback caused by Phytophthora agathidicida is a serious problem affecting forests throughout the upper North Island. A potential control tool is the use of phosphorus acid (phosphite) as a foliar spray. This study investigates various commercial formulations of phosphorus acid in combination with adjuvants, for their potential uptake into kauri foliage. Large differences were seen in the uptake between the upper (adaxial) and lower (abaxial) leaf surfaces. The upper kauri leaf surface gave negligible uptake (<5%) while the lower surface had >65% uptake across all formulations tested. From these results, the potential for spray operations is discussed.

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Thurston, Alana M., Lauren Waller, Leo Condron, and Amanda Black. "Sensitivity of the soil-borne pathogen Phytophthora agathidicida, the causal agent of kauri dieback, to the anti-oomycete fungicides ethaboxam, fluopicolide, mandipropamid, and oxathiapiprolin." New Zealand Plant Protection 75 (May 3, 2022): 14–18. http://dx.doi.org/10.30843/nzpp.2022.75.11751.

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The oomycete Phytophthora agathidicida is the causal agent of kauri dieback, which threatens the survival of endemic kauri (Agathis australis) forests in Aotearoa|New Zealand. Current chemical control of P. agathidicida involves the application of either a mixture of halogenated tertiary amines or phosphite salts with some success, but neither treatment cures the disease. Recently, four anti-oomycete fungicides, all with different modes of action, have become commercially available. Here, we determined the inhibition potential of these fungicides on three P. agathidicida isolates, using agar dilution assays. The average concentration required to inhibit mycelial growth by 50% (EC50) for ethaboxam, fluopicolide, and mandipropamid was 0.0916, 0.372, and 0.0196 µg/mL, respectively. Inhibition of P. agathidicida mycelia by oxathiapiprolin and its commercial formulation, Zorvec® Enicade®, was 0.000152 and 0.000309 µg/mL, respectively. Based on the EC50 values reported in this study, these fungicides are the most effective inhibitors of P. agathidicida mycelia when compared to previously screened fungicides, natural products, and plant extracts. Thus, their performance in this initial screening supports further research into their potential use as a kauri dieback management tool.

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Horner, I. J., E. G. Hough, and M. B. Horner. "Forest efficacy trials on phosphite for control of kauri dieback." New Zealand Plant Protection 68 (January 8, 2015): 7–12. http://dx.doi.org/10.30843/nzpp.2015.68.5791.

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In 2012 trials were established in four kauri forest sites severely affected by kauri dieback (Phytophthora agathidicida P taxon Agathis PTA) to determine the potential of phosphorous acid (phosphite) as a control tool Baseline assessments of 162 trial trees included canopy disease rating trunk lesion dimensions and lesion activity (recent bleeding/ 20cm intervals around the trunk Control trees were left untreated After 1 year half the previously injected trees were reinjected in all cases with 75 phosphite Phytotoxicity symptoms (leaf yellowing browning or leaf/twig abscission) were noted in some phosphiteinjected trees particularly where the 20 concentration was used After 3 years many more trunk lesions remained active (expressing ooze continued expansion) in untreated trees (585) than in phosphitetreated trees (08) Average lesion expansion after 3 years was 127 cm in untreated and 04 cm in phosphitetreated trees

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Herewini, Echo M., Peter M. Scott, Nari M. Williams, and Rosie E. Bradshaw. "In vitro assays of Phytophthora agathidicida on kauri leaves suggest variability in pathogen virulence and host response." New Zealand Plant Protection 71 (June 8, 2018): 285–88. http://dx.doi.org/10.30843/nzpp.2018.71.127.

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Phytophthora agathidicida is an aggressive soil-borne oomycete pathogen that kills New Zealand kauri trees (Agathis australis). When artificially inoculated, P. agathidicida causes lesions on leaves as well as roots, providing a non-invasive method for virulence screening. However, little is known about the extents to which the pathogen varies in virulence and kauri trees vary in disease susceptibility. Three isolates of P. agathidicida grown in culture were inoculated onto detached leaves from six kauri trees. Visible disease lesions were measured and the extent of asymptomatic leaf colonisation determined by culturing. All six trees were susceptible to P. agathidicida, but one showed higher susceptibility than the others. The pathogen also showed variability in virulence among isolates. Asymptomatic colonisation of leaf tissue was also found, suggesting a latent or biotrophic phase for the pathogen. Although further work is needed, the variability of both pathogen virulence and host susceptibility have important implications for management of kauri dieback. Furthermore, asymptomatic colonisation of kauri tissues suggests that P. agathidicida could be present outside of regions with visible disease symptoms.

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Meiforth, Jane J., Henning Buddenbaum, Joachim Hill, James Shepherd, and David A. Norton. "Detection of New Zealand Kauri Trees with AISA Aerial Hyperspectral Data for Use in Multispectral Monitoring." Remote Sensing 11, no. 23 (December 2, 2019): 2865. http://dx.doi.org/10.3390/rs11232865.

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The endemic New Zealand kauri trees (Agathis australis) are of major importance for the forests in the northern part of New Zealand. The mapping of kauri locations is required for the monitoring of the deadly kauri dieback disease (Phytophthora agathidicida (PTA)). In this study, we developed a method to identify kauri trees by optical remote sensing that can be applied in an area-wide campaign. Dead and dying trees were separated in one class and the remaining trees with no to medium stress symptoms were defined in the two classes “kauri” and “other”. The reference dataset covers a representative selection of 3165 precisely located crowns of kauri and 21 other canopy species in the Waitakere Ranges west of Auckland. The analysis is based on an airborne hyperspectral AISA Fenix image (437–2337 nm, 1 m2 pixel resolution). The kauri spectra show characteristically steep reflectance and absorption features in the near-infrared (NIR) region with a distinct long descent at 1215 nm, which can be parameterised with a modified Normalised Water Index (mNDWI-Hyp). With a Jeffries–Matusita separability over 1.9, the kauri spectra can be well separated from 21 other canopy vegetation spectra. The Random Forest classifier performed slightly better than Support Vector Machine. A combination of the mNDWI-Hyp index with four additional spectral indices with three red to NIR bands resulted in an overall pixel-based accuracy (OA) of 91.7% for crowns larger 3 m diameter. While the user’s and producer’s accuracies for the class “kauri” with 94.6% and 94.8% are suitable for management purposes, the separation of “dead/dying trees” from “other” canopy vegetation poses the main challenge. The OA can be improved to 93.8% by combining “kauri” and “dead/dying” trees in one class, separate classifications for low and high forest stands and a binning to 10 nm bandwidths. Additional wavelengths and their respective indices only improved the OA up to 0.6%. The method developed in this study allows an accurate location of kauri trees for an area-wide mapping with a five-band multispectral sensor in a representative selection of forest ecosystems.

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Meiforth, Jane J., Henning Buddenbaum, Joachim Hill, James D. Shepherd, and John R. Dymond. "Stress Detection in New Zealand Kauri Canopies with WorldView-2 Satellite and LiDAR Data." Remote Sensing 12, no. 12 (June 12, 2020): 1906. http://dx.doi.org/10.3390/rs12121906.

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New Zealand kauri trees are threatened by the kauri dieback disease (Phytophthora agathidicida (PA)). In this study, we investigate the use of pan-sharpened WorldView-2 (WV2) satellite and Light Detection and Ranging (LiDAR) data for detecting stress symptoms in the canopy of kauri trees. A total of 1089 reference crowns were located in the Waitakere Ranges west of Auckland and assessed by fieldwork and the interpretation of aerial images. Canopy stress symptoms were graded based on five basic stress levels and further refined for the first symptom stages. The crown polygons were manually edited on a LiDAR crown height model. Crowns with a mean diameter smaller than 4 m caused most outliers with the 1.8 m pixel size of the WV2 multispectral bands, especially at the more advanced stress levels of dying and dead trees. The exclusion of crowns with a diameter smaller than 4 m increased the correlation in an object-based random forest regression from 0.85 to 0.89 with only WV2 attributes (root mean squared error (RMSE) of 0.48, mean absolute error (MAE) of 0.34). Additional LiDAR attributes increased the correlation to 0.92 (RMSE of 0.43, MAE of 0.31). A red/near-infrared (NIR) normalised difference vegetation index (NDVI) and a ratio of the red and green bands were the most important indices for an assessment of the full range of stress symptoms. For detection of the first stress symptoms, an NDVI on the red-edge and green bands increased the performance. This study is the first to analyse the use of spaceborne images for monitoring canopy stress symptoms in native New Zealand kauri forest. The method presented shows promising results for a cost-efficient stress monitoring of kauri crowns over large areas. It will be tested in a full processing chain with automatic kauri identification and crown segmentation.

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Byers, Alexa-Kate, Leo Condron, Maureen O'Callaghan, Nick Waipara, and Amanda Black. "Identification of Burkholderia and Penicillium isolates from kauri (Agathis australis) soils that inhibit the mycelial growth of Phytophthora agathidicida." New Zealand Plant Protection 74, no. 1 (August 30, 2021): 42–54. http://dx.doi.org/10.30843/nzpp.2021.74.11736.

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Phytophthora agathidicida is a highly virulent pathogen of kauri (Agathis australis) and the causal agent of dieback disease in New Zealand’s kauri forests. This study aimed to identify microbial isolates isolated from kauri forest soils that inhibited the growth of P. agathidicida. Three different forms of in vitro bioassays were used to assess the inhibition of each isolate on the mycelial growth of P. agathidicida. Furthermore, head space (HS) solid-phase micro-extraction coupled with gas chromatography-mass spectrometry (SPME-GCMS) was performed to identify if the microbial isolates emitted volatile organic compounds (VOCs), which may be contributing to inhibition. This research identified several bacterial isolates belonging to the genus Burkholderia that inhibited the mycelial growth of P. agathidicida. Furthermore, several VOCs produced by these isolates were putatively identified, which may be responsible for the inhibition observed in the bioassays. Several isolates of Penicillium were identified that inhibit Phytophthora agathidicida, with the culture filtrate of one isolate being found to strongly inhibit P. agathidicida mycelial growth. These isolates of Burkholderia and Penicillium appear to exhibit multiple modes of antagonism against P. agathidicida, including microbial competition and the production of diffusible and volatile anti-microbial compounds. Although further research is needed to better define their mechanisms of inhibition, these findings have identified candidate microbial antagonists of P. agathidicida.

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Guo, Yanan, Pierre‐Yves Dupont, Carl H. Mesarich, Bo Yang, Rebecca L. McDougal, Preeti Panda, Paul Dijkwel, et al. "Functional analysis of RXLR effectors from the New Zealand kauri dieback pathogen Phytophthora agathidicida." Molecular Plant Pathology 21, no. 9 (July 8, 2020): 1131–48. http://dx.doi.org/10.1111/mpp.12967.

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Meiforth, Jane J., Henning Buddenbaum, Joachim Hill, and James Shepherd. "Monitoring of Canopy Stress Symptoms in New Zealand Kauri Trees Analysed with AISA Hyperspectral Data." Remote Sensing 12, no. 6 (March 13, 2020): 926. http://dx.doi.org/10.3390/rs12060926.

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The endemic New Zealand kauri trees (Agathis australis) are under threat by the deadly kauri dieback disease (Phytophthora agathidicida (PA)). This study aimed to identify spectral index combinations for characterising visible stress symptoms in the kauri canopy. The analysis is based on an aerial AISA hyperspectral image mosaic and 1258 reference crowns in three study sites in the Waitakere Ranges west of Auckland. A field-based assessment scheme for canopy stress symptoms (classes 1–5) was further optimised for use with RGB aerial images. A combination of four indices with six bands in the spectral range 450–1205 nm resulted in a correlation of 0.93 (mean absolute error 0.27, RMSE 0.48) for all crown sizes. Comparable results were achieved with five indices in the 450–970 nm region. A Random Forest (RF) regression gave the most accurate predictions while a M5P regression tree performed nearly as well and a linear regression resulted in slightly lower correlations. Normalised Difference Vegetation Indices (NDVI) in the near-infrared / red spectral range were the most important index combinations, followed by indices with bands in the near-infrared spectral range from 800 to 1205 nm. A test on different crown sizes revealed that stress symptoms in smaller crowns with denser foliage are best described in combination with pigment-sensitive indices that include bands in the green and blue spectral range. A stratified approach with individual models for pre-segmented low and high forest stands improved the overall performance. The regression models were also tested in a pixel-based analysis. A manual interpretation of the resulting raster map with stress symptom patterns observed in aerial imagery indicated a good match. With bandwidths of 10 nm and a maximum number of six bands, the selected index combinations can be used for large-area monitoring on an airborne multispectral sensor. This study establishes the base for a cost-efficient, objective monitoring method for stress symptoms in kauri canopies, suitable to cover large forest areas with an airborne multispectral sensor.

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Winkworth, Richard C., Stanley E. Bellgard, Patricia A. McLenachan, and Peter J. Lockhart. "The mitogenome of Phytophthora agathidicida: Evidence for a not so recent arrival of the “kauri killing” Phytophthora in New Zealand." PLOS ONE 16, no. 5 (May 21, 2021): e0250422. http://dx.doi.org/10.1371/journal.pone.0250422.

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Phytophthora agathidicida is associated with a root rot that threatens the long-term survival of the iconic New Zealand kauri. Although it is widely assumed that this pathogen arrived in New Zealand post-1945, this hypothesis has yet to be formally tested. Here we describe evolutionary analyses aimed at evaluating this and two alternative hypotheses. As a basis for our analyses, we assembled complete mitochondrial genome sequences from 16 accessions representing the geographic range of P. agathidicida as well as those of five other members of Phytophthora clade 5. All 21 mitogenome sequences were very similar, differing little in size with all sharing the same gene content and arrangement. We first examined the temporal origins of genetic diversity using a pair of calibration schemes. Both resulted in similar age estimates; specifically, a mean age of 303.0–304.4 years and 95% HPDs of 206.9–414.6 years for the most recent common ancestor of the included isolates. We then used phylogenetic tree building and network analyses to investigate the geographic distribution of the genetic diversity. Four geographically distinct genetic groups were recognised within P. agathidicida. Taken together the inferred age and geographic distribution of the sampled mitogenome diversity suggests that this pathogen diversified following arrival in New Zealand several hundred to several thousand years ago. This conclusion is consistent with the emergence of kauri dieback disease being a consequence of recent changes in the relationship between the pathogen, host, and environment rather than a post-1945 introduction of the causal pathogen into New Zealand.

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Bassett, I. E., I. J. Horner, E. G. Hough, F. M. Wolber, B. Egeter, M. C. Stanley, and C. R. Krull. "Ingestion of infected roots by feral pigs provides a minor vector pathway for kauri dieback disease Phytophthora agathidicida." Forestry: An International Journal of Forest Research 90, no. 5 (April 12, 2017): 640–48. http://dx.doi.org/10.1093/forestry/cpx019.

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Winkworth, Richard C., Briana C. W. Nelson, Stanley E. Bellgard, Chantal M. Probst, Patricia A. McLenachan, and Peter J. Lockhart. "A LAMP at the end of the tunnel: A rapid, field deployable assay for the kauri dieback pathogen, Phytophthora agathidicida." PLOS ONE 15, no. 1 (January 24, 2020): e0224007. http://dx.doi.org/10.1371/journal.pone.0224007.

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Bradshaw, R. E., S. E. Bellgard, A. Black, B. R. Burns, M. L. Gerth, R. L. McDougal, P. M. Scott, et al. "Phytophthora agathidicida : research progress, cultural perspectives and knowledge gaps in the control and management of kauri dieback in New Zealand." Plant Pathology 69, no. 1 (November 6, 2019): 3–16. http://dx.doi.org/10.1111/ppa.13104.

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Nishijima, K. A., P. A. Follett, B. C. Bushe, and M. A. Nagao. "First Report of Lasmenia sp. and Two Species of Gliocephalotrichum on Rambutan in Hawaii." Plant Disease 86, no. 1 (January 2002): 71. http://dx.doi.org/10.1094/pdis.2002.86.1.71c.

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Rambutan (Nephelium lappaceum L.) is a tropical fruit grown in Hawaii for the exotic fruit market. Fruit rot was observed periodically during 1998 and 1999 from two islands, Hawaii and Kauai, and severe fruit rot was observed during 2000 in orchards in Kurtistown and Papaikou on Hawaii. Symptoms were characterized by brown-to-black, water-soaked lesions on the fruit surface that progressed to blackening and drying of the pericarp, which often split and exposed the aril (flesh). In certain cultivars, immature, small green fruits were totally mummified. Rambutan trees with high incidence of fruit rot also showed symptoms of branch dieback and leaf spot. Lasmenia sp. Speg. sensu Sutton, identified by Centraalbureau voor Schimmelcultures (Baarn, the Netherlands), was isolated from infected fruit and necrotic leaves. Also associated with some of the fruit rot and dieback symptoms were Gliocephalotrichum simplex (J.A. Meyer) B. Wiley & E. Simmons, and G. bulbilium J.J. Ellis & Hesseltine. G. simplex was isolated from infected fruit, and G. bulbilium was isolated from discolored vascular tissues and infected fruit. Identification of species of Gliocephalotrichum was based on characteristics of conidiophores, sterile hairs, and chlamydospores (1,4). Culture characteristics were distinctive on potato dextrose agar (PDA), where the mycelium of G. bulbilium was light orange (peach) without reverse color, while G. simplex was golden-brown to grayish-yellow with dark brown reverse color. Both species produced a fruity odor after 6 days on PDA. In pathogenicity tests, healthy, washed rambutan fruits were wounded, inoculated with 30 μl of sterile distilled water (SDW) or a fungus spore suspension (105 to 106 spores per ml), and incubated in humidity chambers at room temperature (22°C) under continuous fluorescent light. Lasmenia sp. (strain KN-F99-1), G. simplex (strain KN-F2000-1), and G. bulbilium (strains KN-F2001-1 and KN-F2001-2) produced fruit rot symptoms on inoculated fruit and were reisolated from fruit with typical symptoms, fulfilling Koch's postulates. Controls (inoculated with SDW) had lower incidence or developed less severe symptoms than the fungus treatments. Inoculation tests were conducted at least twice. To our knowledge, this is the first report of Lasmenia sp. in Hawaii and the first report of the genus Gliocephalotrichum on rambutan in Hawaii. These pathogens are potentially economically important to rambutan in Hawaii. G. bulbilium has been reported previously on decaying wood of guava (Psidium guajava L.) in Hawaii (2), and the fungus causes field and postharvest rots of rambutan fruit in Thailand (3). References: (1) J. J. Ellis and C. W. Hesseltine. Bull. Torrey Bot. Club 89:21, 1962. (2) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (3) N. Visarathanonth and L. L. Ilag. Pages 51–57 in: Rambutan: Fruit Development, Postharvest Physiology and Marketing in ASEAN. ASEAN Food Handling Bureau, Kuala Lumpur, Malaysia, 1987. (4) B. J. Wiley and E. G. Simmons. Mycologia 63:575, 1971.

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Lacey, Randy F., Michael J. Fairhurst, Kaitlyn J. Daley, Te Amohaere Ngata-Aerengamate, Haileigh R. Patterson, Wayne M. Patrick, and Monica L. Gerth. "Assessing the effectiveness of oxathiapiprolin toward Phytophthora agathidicida, the causal agent of kauri dieback disease." FEMS Microbes 2 (2021). http://dx.doi.org/10.1093/femsmc/xtab016.

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ABSTRACT Phytophthora species cause disease and devastation of plants in ecological and horticultural settings worldwide. A recently identified species, Phytophthoraagathidicida, infects and ultimately kills the treasured kauri trees (Agathis australis) that are endemic to New Zealand. Currently, there are few options for managing kauri dieback disease. In this study, we sought to assess the efficacy of the oomycide oxathiapiprolin against several life cycle stages of two geographically distinct P. agathidicida isolates. The effective concentration to inhibit 50% of mycelial growth (EC50) was determined to be ∼0.1 ng/ml, indicating that P. agathidicida mycelia are more sensitive to oxathiapiprolin than those from most other Phytophthora species that have been studied. Oxathiapiprolin was also highly effective at inhibiting the germination of zoospores (EC50 = 2–9 ng/ml for the two isolates) and oospores (complete inhibition at 100 ng/ml). In addition, oxathiapiprolin delayed the onset of detached kauri leaf infection in a dose-dependent manner. Collectively, the results presented here highlight the significant potential of oxathiapiprolin as a tool to aid in the control of kauri dieback disease.

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Byers, Alexa-Kate, Leo Condron, Tom Donavan, Maureen O'Callaghan, Taoho Patuawa, Nick Waipara, and Amanda Black. "Soil microbial diversity in adjacent forest systems – contrasting native, old growth kauri (Agathis australis) forest with exotic pine (Pinus radiata) plantation forest." FEMS Microbiology Ecology 96, no. 5 (March 17, 2020). http://dx.doi.org/10.1093/femsec/fiaa047.

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ABSTRACT Globally, the conversion of primary forests to plantations and agricultural landscapes is a common land use change. Kauri (Agathis australis) is one of the most heavily impacted indigenous tree species of New Zealand with <1% of primary forest remaining as fragments adjacent to pastoral farming and exotic forest plantations. By contrasting two forest systems, we investigated if the fragmentation of kauri forests and introduction of pine plantations (Pinus radiata) are significantly impacting the diversity and composition of soil microbial communities across Waipoua kauri forest, New Zealand. Using next generation based 16S rRNA and ITS gene region sequencing, we identified that fungal and bacterial community composition significantly differed between kauri and pine forest soils. However, fungal communities displayed the largest differences in diversity and composition. This research revealed significant shifts in the soil microbial communities surrounding remnant kauri fragments, including the loss of microbial taxa with functions in disease suppression and plant health. Kauri dieback disease, caused by Phytophthora agathidicida, currently threatens the kauri forest ecosystem. Results from this research highlight the need for further investigations into how changes to soil microbial diversity surrounding remnant kauri fragments impact tree health and disease expression.

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Lindsay, Nicole, Andrea Grant, Nick Bowmast, Hugh Benson, and Simon Wegner. "Pro-Environmental Behaviour in Relation to Kauri Dieback: When Place Attachment Is Not Enough." Society & Natural Resources, October 18, 2022, 1–19. http://dx.doi.org/10.1080/08941920.2022.2135153.

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Stanley, Rebecca, and Wayne Dymond. "Reducing risk to wild ecosystems in nursery production." Sibbaldia: the International Journal of Botanic Garden Horticulture, no. 19 (November 6, 2020). http://dx.doi.org/10.24823/sibbaldia.2020.283.

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The implication of the nursery trade in the historic movement of the pathogen that causes kauri dieback (Phytophthora agathidicida) instigated a review of nursery biosecurity procedures at Auckland Botanic Gardens. The nursery grows 65 000 native plants a year which are planted at restoration sites throughout Auckland. Threatened plants are also grown in the nursery and returned to the wild. The nursery biosecurity project resulted in a manual of protocols, supported by infrastructure upgrades, to ensure the nursery takes all practicable steps to ensure there is as little risk as possible to natural ecosystems through nursery practices. This work also demonstrates the important role of Botanic Gardens in providing education and advocacy for such schemes in all nurseries.

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Cox, Murray P., Yanan Guo, David J. Winter, Diya Sen, Nicholas C. Cauldron, Jason Shiller, Ellie L. Bradley, et al. "Chromosome-level assembly of the Phytophthora agathidicida genome reveals adaptation in effector gene families." Frontiers in Microbiology 13 (November 2, 2022). http://dx.doi.org/10.3389/fmicb.2022.1038444.

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Abstract:

Phytophthora species are notorious plant pathogens, with some causing devastating tree diseases that threaten the survival of their host species. One such example is Phytophthora agathidicida, the causal agent of kauri dieback – a root and trunk rot disease that kills the ancient, iconic and culturally significant tree species, Agathis australis (New Zealand kauri). A deeper understanding of how Phytophthora pathogens infect their hosts and cause disease is critical for the development of effective treatments. Such an understanding can be gained by interrogating pathogen genomes for effector genes, which are involved in virulence or pathogenicity. Although genome sequencing has become more affordable, the complete assembly of Phytophthora genomes has been problematic, particularly for those with a high abundance of repetitive sequences. Therefore, effector genes located in repetitive regions could be truncated or missed in a fragmented genome assembly. Using a combination of long-read PacBio sequences, chromatin conformation capture (Hi-C) and Illumina short reads, we assembled the P. agathidicida genome into ten complete chromosomes, with a genome size of 57 Mb including 34% repeats. This is the first Phytophthora genome assembled to chromosome level and it reveals a high level of syntenic conservation with the complete genome of Peronospora effusa, the only other completely assembled genome sequence of an oomycete. All P. agathidicida chromosomes have clearly defined centromeres and contain candidate effector genes such as RXLRs and CRNs, but in different proportions, reflecting the presence of gene family clusters. Candidate effector genes are predominantly found in gene-poor, repeat-rich regions of the genome, and in some cases showed a high degree of duplication. Analysis of candidate RXLR effector genes that occur in multicopy gene families indicated half of them were not expressed in planta. Candidate CRN effector gene families showed evidence of transposon-mediated recombination leading to new combinations of protein domains, both within and between chromosomes. Further analysis of this complete genome assembly will help inform new methods of disease control against P. agathidicida and other Phytophthora species, ultimately helping decipher how Phytophthora pathogens have evolved to shape their effector repertoires and how they might adapt in the future.

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Journal articles on the topic 'Kauri Dieback'

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