ORCID Profile
0000-0003-0493-4954
Current Organisations
The University of Auckland
,
New Zealand Institute for Plant and Food Research Ltd
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Publisher: Springer Science and Business Media LLC
Date: 27-08-2014
Publisher: Informa UK Limited
Date: 26-07-2019
Publisher: Wiley
Date: 29-04-2014
DOI: 10.1111/JPH.12257
Publisher: Elsevier BV
Date: 06-2006
DOI: 10.1016/J.MYCRES.2006.04.003
Abstract: Microarray-based detection is limited by variable and inconsistent hybridization intensities across the ersity of probes used in each array. In this paper, we introduce a novel concept for the differentiation of detection targets using duplex melting kinetics. A microarray assay was developed on a PamChip microarray enabling the differentiation of target Phytophthora species using the melting kinetics of probe-target duplexes. In the majority of cases the hybridization kinetics of target and non-target duplexes differed significantly. Analysis of the melting kinetics of duplexes formed by probes with target and non-target DNA was found to be an effective method for determining specific hybridization and was independent of fluctuations in hybridization signal intensity. This form of analysis was more robust than the traditional approach based on hybridization intensity, and enabled the detection of in idual Phytophthora species and mixtures thereof.
Publisher: Wiley
Date: 04-2009
Publisher: Public Library of Science (PLoS)
Date: 28-05-2019
Publisher: Scion
Date: 24-05-2014
Publisher: Scion
Date: 23-05-2014
Publisher: Scion
Date: 23-05-2014
Publisher: Wiley
Date: 23-12-2020
Publisher: Springer Science and Business Media LLC
Date: 08-04-2019
Publisher: Elsevier BV
Date: 11-2019
Publisher: Public Library of Science (PLoS)
Date: 10-12-2018
Publisher: Scion
Date: 12-2014
Publisher: Informa UK Limited
Date: 27-03-2009
DOI: 10.1080/10408410902831518
Abstract: Species of the genus Phytophthora are arguably the most destructive plant pathogens causing widespread damage to many horticultural and ornamental species, and to native ecosystems throughout the world. Globalization has increased the volume of plants being transported over long distances and has increased the spread of Phytophthora species. As traditional detection methods such as baiting or direct isolation are incapable of handling the large volume of material to be tested, researchers have developed more rapid and specific antibody and DNA based tests. This review compares the performance of the different types of tests used for detection of Phytophthora.
Publisher: Scientific Societies
Date: 05-2015
Publisher: Scientific Societies
Date: 11-2019
DOI: 10.1094/PHYTO-12-18-0479-R
Abstract: The emergence of Phytophthora pluvialis as a foliar pathogen of Douglas fir in New Zealand and the Pacific Northwest United States has raised questions about its interaction with the widespread Swiss needle cast (SNC) disease. During Spring 2017, we repeatedly s led 30 trees along an environmental gradient in each region and 292 additional trees in a longitudinal transect to assess the P. pluvialis epidemic and the association between P. pluvialis and Nothophaeocryptopus gaeumannii, which are causal agents of SNC. Both pathogens were consistently more abundant in the host’s exotic environment in New Zealand. In both areas, the two pathogens co-exist in different spatial scales for regions and needles. The relative abundance of both pathogens was negatively correlated in the Pacific Northwest, where both presumably have co-existed for longer. Our findings confirmed the interaction of P. pluvialis and N. gaeumannii as foliar pathogens of Douglas fir and suggest a within-site spatial variation in the Pacific Northwest.
Publisher: Wiley
Date: 06-11-0001
DOI: 10.1111/PPA.13104
Publisher: Springer Science and Business Media LLC
Date: 09-02-2019
Publisher: Wiley
Date: 30-01-2018
DOI: 10.1111/PPA.12812
Publisher: Wiley
Date: 19-04-2016
DOI: 10.1111/PPL.12442
Abstract: Phytophthora plant pathogens cause tremendous damage in planted and natural systems worldwide. Phosphite is one of the only effective chemicals to control broad-scale Phytophthora disease. Little work has been done on the phytotoxic effects of phosphite application on plant communities especially in combination with plant physiological impacts. Here, we tested the phytotoxic impact of phosphite applied as foliar spray at 0, 12, 24 and 48 kg a.i. ha(-1) . Eighteen-month-old saplings of 13 conifer and angiosperm species native to New Zealand, and two exotic coniferous species were treated and the development of necrotic tissue and chlorophyll-a-fluorescence parameters (optimal quantum yield, Fv /Fm effective quantum yield of photosystem II, ΦPSII ) were assessed. In addition, stomatal conductance (gs ) was measured on a subset of six species. Significant necrosis assessed by digital image analysis occurred in only three species: in the lauraceous canopy tree Beilschmiedia tawa (8-14%) and the understory shrub Dodonaea viscosa (5-7%) across phosphite concentrations and solely at the highest concentration in the myrtaceous pioneer shrub Leptospermum scoparium (66%). In non-necrotic tissue, Fv /Fm , ΦPSII and gs remained unaffected by the phosphite treatment. Overall, our findings suggest minor phytotoxic effects resulting from foliar phosphite application across erse taxa and regardless of concentration. This study supports the large-scale use of phosphite as a management tool to control plant diseases caused by Phytophthora pathogens in plantations and natural ecosystems. Long-term studies are required to ascertain potential ecological impacts of repeated phosphite applications.
Publisher: Wiley
Date: 26-06-2017
DOI: 10.1111/NPH.14657
Abstract: Invasions of alien plants are typically studied as invasions of in idual species, yet interactions between plants and symbiotic fungi (mutualists and potential pathogens) affect plant survival, physiological traits, and reproduction and hence invasion success. Studies show that plant–fungal associations are frequently key drivers of plant invasion success and impact, but clear conceptual frameworks and integration across studies are needed to move beyond a series of case studies towards a more predictive understanding. Here, we consider linked plant–fungal invasions from the perspective of plant and fungal origin, simplified to the least complex representations or ‘motifs’. By characterizing these interaction motifs, parallels in invasion processes between pathogen and mutualist fungi become clear, although the outcomes are often opposite in effect. These interaction motifs provide hypotheses for fungal‐driven dynamics behind observed plant invasion trajectories. In some situations, the effects of plant–fungal interactions are inconsistent or negligible. Variability in when and where different interaction motifs matter may be driven by specificity in the plant–fungal interaction, the size of the effect of the symbiosis (negative to positive) on plants and the dependence (obligate to facultative) of the plant−fungal interaction. Linked plant–fungal invasions can transform communities and ecosystem function, with potential for persistent legacies preventing ecosystem restoration. Contents Summary 1314 I. Introduction 1315 II. Simplification of complex networks into interaction motifs 1316 III. Plant–fungal interactions and plant invasion dynamics 1322 IV. Predicting where plant–fungal interactions matter: plant−symbiont specificity, dependence and effect size 1323 V. Spatial context of linked plant–fungal invasions 1325 VI. Impacts of linked plant–fungal invasions on ecosystem processes 1326 VII. Management implications 1326 VIII. Conclusions 1327 Acknowledgements 1328 References 1328
Publisher: Scientific Societies
Date: 08-2019
DOI: 10.1094/PDIS-07-18-1247-RE
Abstract: Red needle cast is a significant foliar disease of commercial stands of Pinus radiata caused by Phytophthora pluvialis in New Zealand. The effect of copper, applied as a foliar spray of cuprous oxide at a range of doses between 0 and 1.72 kg ha −1 , was investigated in two controlled trials with potted plants and in an operational trial with mature P. radiata. In all trials, lesions formed on needles after artificial exposure to the infecting propagules (zoospores) of P. pluvialis were used to determine treatment efficacy, with the number and/or length of lesions as the dependent variable. Results across all trials indicated that cuprous oxide was highly effective at reducing infection of P. radiata with P. pluvialis. Application rates equivalent to ≥0.65 kg ha −1 significantly reduced infection levels relative to a control treatment, with foliar surface copper levels as low as 13 to 26 mg kg −1 of needle tissue preventing infection. Greater copper content was associated with a reduction in the proportion of needles with P. pluvialis lesions, with the probability of lesions developing decreasing approximately 1% for every 1 unit (in milligrams per kilogram) increase in copper content. Over a 90-day period, surface copper content declined to 30% of that originally applied, indicating an approximate period of treatment efficacy of 3 months. Our findings highlight the potential of cuprous oxide for the control of red needle cast in P. radiata stands. Further information about the optimal field dose, timing, and the frequency of foliar cuprous oxide application is key to prevent infection and also reduce the build up of inoculum during severe outbreaks of this pathogen.
Publisher: New Zealand Plant Protection Society
Date: 08-06-2018
DOI: 10.30843/NZPP.2018.71.127
Abstract: 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.
Publisher: Elsevier BV
Date: 03-2016
Publisher: Elsevier BV
Date: 08-2010
Publisher: Springer Science and Business Media LLC
Date: 27-06-2018
Publisher: Wiley
Date: 03-03-2020
DOI: 10.1111/EFP.12588
Publisher: Springer Science and Business Media LLC
Date: 2009
DOI: 10.1071/AP09044
Publisher: Wiley
Date: 14-02-2019
DOI: 10.1111/EFP.12502
Publisher: Springer Science and Business Media LLC
Date: 30-09-2010
DOI: 10.1007/S00438-010-0579-7
Abstract: Phosphite, an analog of phosphate is used to control oomycete diseases on a wide range of horticultural crops and in native ecosystems. In this study, we investigated morphological and transcriptional changes induced in Phytophthora cinnamomi by phosphite. Cytological observations revealed that phosphite caused hyphal distortions and lysis of cell walls and had an adverse effect on hyphal growth. At the molecular level, the expression levels of 43 transcripts were changed. Many of these encoded proteins involved in cell wall synthesis, or cytoskeleton functioning. The results of both the microscopic and molecular investigations are consistent with phosphite inhibiting the function of the cytoskeleton and cell wall synthesis.
Publisher: Australian Mathematical Publishing Association, Inc.
Date: 12-03-2018
Publisher: New Zealand Plant Protection Society
Date: 08-01-2014
DOI: 10.30843/NZPP.2014.67.5721
Abstract: Ten years ago there were no known foliar diseases caused by Phytophthora on pine trees worldwide Since then two significant Phytophthora diseases have emerged on radiata pine one of which is only known in New Zealand Red needle cast is a disease caused by the pathogen Phytophthora pluvialis which is thought to have originated from northwestern USA This paper reviews the challenges the New Zealand forestry industry faces when dealing with this disease and evaluates the management options such as chemical control biological control and breeding programmes being investigated to minimise its effect on forest productivity The distribution of the pathogen in New Zealand and research that shows bark logs and wood are free of the pathogen therefore unlikely to pose biosecurity threats through trade in these products are also outlined
Publisher: Wiley
Date: 09-02-2017
DOI: 10.1111/EFP.12327
Publisher: Scientific Societies
Date: 2021
DOI: 10.1094/PHYTO-06-20-0232-FI
Abstract: Phytophthora pluvialis is an oomycete that was first isolated from soil, water, and tree foliage in mixed Douglas-fir−tanoak forests of the U.S. Pacific Northwest (PNW). It was then identified as the causal agent of red needle cast of radiata pine (Pinus radiata) in New Zealand (NZ). Genotyping-by-sequencing was used to obtain 1,543 single nucleotide polymorphisms across 145 P. pluvialis isolates to characterize the population structure in the PNW and NZ. We tested the hypothesis that P. pluvialis was introduced to NZ from the PNW using genetic distance measurements and population structure analyses among locations between countries. The low genetic distance, population heterozygosity, and lack of geographic structure in NZ suggest a single colonization event from the United States followed by clonal expansion in NZ. The PNW Coast Range was proposed as a presumptive center of origin of the currently known distribution of P. pluvialis based on its geographic range and position as the central cluster in a minimum spanning network. The Coastal cluster of isolates were located at the root of every U.S. cluster and emerged earlier than all NZ clusters. The Coastal cluster had the highest degree of heterozygosity (Hs = 0.254) and median pairwise genetic distance (0.093) relative to any other cluster. Finally, the rapid host ersification between closely related isolates of P. pluvialis in NZ indicate that this pathogen has the potential to infect a broader range of hosts than is currently recognized.
Publisher: Springer Science and Business Media LLC
Date: 29-05-2019
Publisher: Scientific Societies
Date: 07-2017
DOI: 10.1094/PDIS-12-16-1738-RE
Abstract: Phytophthora pluvialis is associated with early defoliation and shoot dieback in Douglas-fir in Oregon and New Zealand. In 2013, P. pluvialis was described from mixed tanoak-Douglas-fir forests in the Pacific Northwest and concurrently recognized as the main causal agent of red needle cast (RNC) in New Zealand radiata pine plantations. Little is known about its infection cycle and impact on host physiology. P. pluvialis studies in Douglas-fir are challenging due to the ubiquitous presence of the endophyte Phaeocryptopus gaeumannii, which produces similar symptoms and premature defoliation with persistent needle wetness, known as Swiss needle cast (SNC). Nonetheless, our study showed P. pluvialis infection in the presence of SNC. Exclusive expression of P. pluvialis is difficult to achieve as both diseases are promoted by high humidity. Here we established a ‘dry leaf’ strategy to suppress SNC when inoculating Douglas-fir needles for RNC studies. Sheltering plants along with drip irrigation to avoid needle wetness during the P. gaeumannii sporulation period suppressed its development in the new season flush. The diminished endophyte inoculum enabled bias-reduced studies of P. pluvialis impacts on Douglas-fir without the confounding effects of stomatal blockage and premature defoliation caused by P. gaeumannii.
Publisher: Wiley
Date: 05-12-2018
DOI: 10.1111/MPP.12765
Publisher: Elsevier BV
Date: 11-2018
DOI: 10.1016/J.MIMET.2018.10.006
Abstract: A high-throughput assay was developed to screen Phytophthora species for fungicide sensitivity using optical density measurements for unbiased, automated measurement of mycelial growth. The efficacy of the optical density assay (OD) to measure phosphite sensitivity in Phytophthora species was compared to two widely used methods, radial growth (RG) and dry weight (DW) assays. Three isolates of each of Phytophthora cinnamomi, P. multivora and P. pluvialis, with known phosphite exposure and three isolates of each species with no prior phosphite exposure, were screened for phosphite sensitivity using the three assays. Mycelial growth measurements were taken after culturing for 6, 14 and 15 days for the OD, DW and RG assays respectively. Mycelial growth inhibition at 15, 80, 200 and 500 μg/mL phosphite relative to growth on control media was used to determine effective concentration values for 50% growth reduction (EC50). The species varied in their tolerance to phosphite with P. cinnamomi being the least sensitive followed by P. multivora and P. pluvialis. No significant differences in tolerance were found between isolates within the same species using any method. The OD assay produced comparable EC50 values to the RG and DW assays. The growth of the three species was more sensitive to phosphite in the DW than the RG and OD assays, however limited s le throughput and greater variation in measuring small amounts of mycelia in the dry weight assessment increase variability and limits throughput. The OD assay offers a fast method to enable an inventory of chemical resistance and is particularly advantageous for slow growing species as it requires less time and offers greater throughput than existing RG and DW methods.
Publisher: Springer Science and Business Media LLC
Date: 24-01-2013
Publisher: Wiley
Date: 02-03-2021
DOI: 10.1111/EFP.12680
Abstract: New Zealand kauri ( Agathis australis ) trees are culturally, socially and ecologically significant within northern New Zealand's nutrient‐poor podocarp forest ecosystems. Phytophthora agathidicida is an aggressive oomycete pathogen, capable of killing A . australis across its ecological range, causing the disease known as kauri dieback. The pathogen, like many other forest Phytophthora species, commences as a fine root rot which progresses to collar rot and resinous cankers on the lower trunk. In this study, we investigated the eco‐physiological and fine root responses of kauri to infection by P . agathidicida and tested whether the foliar application of micronutrients (manganese and zinc combined, iron alone, or a trace element mix) affects dieback disease expression. Fortnightly assessments of chlorophyll‐ a ‐fluorescence were conducted over 12 weeks, and fine root length and tip numbers were recorded at the end of the experiment. None of the micronutrient treatments had a significant physiological effect regardless of pathogen infection. However, contrary to expectations, pathogen infection caused a significant upregulation in photosynthetic activity over time, as the electron transport rate of infected plants was approximately 26% higher than that of control plants at the end of the trial. These results indicate that an increase in the strength of the below‐ground carbon sink through pathogen consumption of labile carbohydrates (sugars), together with pathogen‐induced root damage, triggered upregulation of photosynthesis in the seedlings. Understanding how P . agathidicida infection affects the physiology and resource allocation in kauri is critical to determining the disease aetiology and management options.
Publisher: Wiley
Date: 08-07-2020
DOI: 10.1111/MPP.12967
Publisher: MDPI AG
Date: 02-02-2018
Location: New Zealand
Start Date: 2013
End Date: 2019
Funder: Ministry for Business Innovation and Employment
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