Behaviour of Phytophthora cinnamomi Zoospores on Roots of Australian Forest Species

1979 ◽  
Vol 27 (6) ◽  
pp. 679 ◽  
Author(s):  
J Hinch ◽  
G Weste
Keyword(s):  
Vascular Tissue ◽  
Root Zone ◽  
Phytophthora Cinnamomi ◽  
Host Susceptibility ◽  
Forest Species ◽  
Native Forests ◽  
Species Specific ◽  
Germ Tubes ◽  
Root Axis

Twenty-three species from Australian native forests were examined in a comparative assay of the chemotaxis of zoospores of Phytophthora cinnamomi towards their roots. Zoospores were attracted to all species tested when within 3-4 mm from the roots. Attraction to wounds and cut ends of roots was also observed. The chemotaxis was neither species-specific nor host-orientated. The root zone which attracted most zoospores was the region of elongation for most species, but this varied and is described and illustrated for the different species. Encysted zoospores produced one and occasionally two germ tubes which were normally orientated towards the root axis. Subsequent penetration of epidermis, cortex and vascular tissue was observed and, like the chemotaxis and chemotropy, was not related to host susceptibility.

scholarly journals A Model-Based Volume Estimator that Accounts for Both Land Cover Misclassification and Model Prediction Uncertainty

2020 ◽  
Vol 12 (20) ◽  
pp. 3360
Author(s):  
Jessica Esteban ◽  
Ronald E. McRoberts ◽  
Alfredo Fernández-Landa ◽  
José Luis Tomé ◽  
Miguel Marchamalo
Keyword(s):  
Forest Inventory ◽  
Laser Scanning ◽  
Specific Area ◽  
Training Data ◽  
Forest Species ◽  
Total Uncertainty ◽  
Estimation Process ◽  
Model Based ◽  
Species Specific ◽  
Field Plots

Forest/non-forest and forest species maps are often used by forest inventory programs in the forest estimation process. For example, some inventory programs establish field plots only on lands corresponding to the forest portion of a forest/non-forest map and use species-specific area estimates obtained from those maps to support the estimation of species-specific volume (V) totals. Despite the general use of these maps, the effects of their uncertainties are commonly ignored with the result that estimates might be unreliable. The goal of this study is to estimate the effects of the uncertainty of forest species maps used in the sampling and estimation processes. Random forest (RF) per-pixel predictions were used with model-based inference to estimate V per unit area for the six main forest species of La Rioja, Spain. RF models for predicting V were constructed using field plot information from the Spanish National Forest Inventory and airborne laser scanning data. To limit the prediction of V to pixels classified as one of the main forest species assessed, a forest species map was constructed using Landsat and auxiliary information. Bootstrapping techniques were implemented to estimate the total uncertainty of the V estimates and accommodated both the effects of uncertainty in the Landsat forest species map and the effects of plot-to-plot sampling variability on training data used to construct the RF V models. Standard errors of species-specific total V estimates increased from 2–9% to 3–22% when the effects of map uncertainty were incorporated into the uncertainty assessment. The workflow achieved satisfactory results and revealed that the effects of map uncertainty are not negligible, especially for open-grown and less frequently occurring forest species for which greater variability was evident in the mapping and estimation process. The effects of forest map uncertainty are greater for species-specific area estimation than for the selection of field plots used to calibrate the RF model. Additional research to generalize the conclusions beyond Mediterranean to other forest environments is recommended.

Explaining variability in parasite aggregation levels among host samples

Parasitology ◽  
2013 ◽  
Vol 140 (4) ◽  
pp. 541-546 ◽  
Author(s):  
ROBERT POULIN
Keyword(s):  
Body Size ◽  
Strong Relationship ◽  
Host Susceptibility ◽  
Helminth Parasites ◽  
Susceptibility To Infection ◽  
Host Body ◽  
Parasite Aggregation ◽  
Using Data ◽  
Species Specific ◽  
Host Body Size

SUMMARYAggregated distributions among individual hosts are a defining feature of metazoan parasite populations. Heterogeneity among host individuals in exposure to parasites or in susceptibility to infection is thought to be the main factor generating aggregation, with properties of parasites themselves explaining some of the variability in aggregation levels observed among species. Here, using data from 410 samples of helminth parasites on fish hosts, I tested the contribution of (i) within-sample variation in host body size, taken as a proxy for variability in host susceptibility, and (ii) parasite taxon and developmental stage, to the aggregated distribution of parasites. Log-transformed variance in numbers of parasites per host was regressed against log mean number across all samples; the strong relationship (r2 = 0·88) indicated that aggregation levels are tightly constrained by mean infection levels, and that only a small proportion of the observed variability in parasite aggregation levels remains to be accounted for by other factors. Using the residuals of this regression as measures of ‘unexplained’ aggregation, a mixed effects model revealed no significant effect of within-sample variation in host body size or of parasite taxon or stage (i.e. juvenile versus adult) on parasite aggregation level within a sample. However, much of the remaining variability in parasite aggregation levels among samples was accounted for by the number of individual hosts examined per sample, and species-specific and study-specific effects reflecting idiosyncrasies of particular systems. This suggests that with most differences in aggregation among samples already explained, there may be little point in seeking universal causes for the remaining variation.

scholarly journals Photosynthetic performance and biochemical adjustments in two co-occurring Mediterranean evergreens, Quercus ilex and Arbutus unedo, differing in salt-exclusion ability

2014 ◽  
Vol 41 (4) ◽  
pp. 391 ◽  
Author(s):  
Lina Fusaro ◽  
Simone Mereu ◽  
Cecilia Brunetti ◽  
Martina Di Ferdinando ◽  
Francesco Ferrini ◽  
...  
Keyword(s):  
Salinity Stress ◽  
Quercus Ilex ◽  
Root Zone ◽  
Metabolic Cost ◽  
Co2 Assimilation ◽  
Leaf Life Span ◽  
Antioxidant Defences ◽  
Arbutus Unedo ◽  
Salt Exclusion ◽  
Species Specific

The responses to mild root zone salinity stress were investigated in two co-occurring Mediterranean woody evergreens, Quercus ilex L. and Arbutus unedo L., which differ in morpho-anatomical traits and strategies to cope with water deficit. The aim was to explore their strategies to allocate potentially toxic ions at organism level, and the consequential physiological and biochemical adjustments. Water and ionic relations, gas exchange and PSII performance, the concentration of photosynthetic pigments, and the activity of antioxidant defences, were measured. Q. ilex displayed a greater capacity to exclude Na+ and Cl– from the leaf than A. unedo, in part as a consequence of greater reductions in transpiration rates. Salt-induced reductions in CO2 assimilation resulted in Q. ilex suffering from excess of light to a greater extent than A. unedo. Consistently, in Q. ilex effective mechanisms of nonphotochemical quenching, also sustained by the lutein epoxide-lutein cycle, operated in response to salinity stress. Q. ilex also displayed a superior capacity to detoxify reactive oxygen species (ROS) than A. unedo. Our data suggest that the ability to exclude salt from actively growing shoot organs depends on the metabolic cost of sustaining leaf construction, i.e. species-specific leaf life-span, and the relative strategies to cope with salt-induced water stress. We discuss how contrasting abilities to restrict the entry and transport of salt in sensitive organs relates with species-specific salt tolerance.

Production of species-specific monoclonal antibodies that react with surface components on zoospores and cysts of Phytophthora nicotianae

1998 ◽  
Vol 44 (12) ◽  
pp. 1161-1170 ◽  
Author(s):  
A V Robold ◽  
A R Hardham
Keyword(s):  
Monoclonal Antibodies ◽  
Cell Lines ◽  
Phytophthora Cinnamomi ◽  
Phytophthora Nicotianae ◽  
The Other ◽  
Hybridoma Cells ◽  
Enzyme Linked Immunosorbent Assay ◽  
Specific Antibodies ◽  
Hybridoma Cell Lines ◽  
Species Specific

Monoclonal antibodies were generated against components on the surface of zoospores and cysts of the Oomycete, Phytophthora nicotianae, with the aim of obtaining antibodies diagnostic for this species of plant pathogen. A dipstick version of an enzyme-linked immunosorbent assay was used to screen hybridoma cell lines produced by following a coimmunization protocol in which a mouse was immunized with Phytophthora nicotianae cysts mixed with murine antisera raised against cysts of Phytophthora cinnamomi and Phytophthora cryptogea. Of the nine hybridoma cells lines which remained positive, five produced antibodies that reacted with species-specific epitopes on the surface of the spores. Immunofluorescence, immunogold, and immunoblot labelling showed that three of the five species-specific antibodies reacted with a polypeptide of relative molecular mass greater than 205 kDa which was distributed over the entire zoospore surface, including that of the two flagella. These antibodies also labelled the surface of cysts to varying degrees. The other two species-specific antibodies bound to the shaft of tubular mastigonemes that form two rows on the anterior flagellum. In immunoblots, one of these antibodies recognised a 40-kDa glycoprotein. Antibodies produced by the other four hybridoma cell lines reacted with all Phytophthora and Pythium species tested. The results (i) showed that the coimmunization technique effectively produced antibodies directed towards components specific for Phytophthora nicotianae in the presence of antigens common to many Phytophthora species, and (ii) revealed for the first time the biochemical nature of molecular constituents of flagellar mastigonemes in the Oomycetes.Key words: cell surface, flagella, immunodiagnostics, mastigonemes, monoclonal antibodies.

scholarly journals Strawberry Anthracnose: Histopathology of Colletotrichum acutatum and C. fragariae

2002 ◽  
Vol 92 (10) ◽  
pp. 1055-1063 ◽  
Author(s):  
Kenneth J. Curry ◽  
Maritza Abril ◽  
Jana B. Avant ◽  
Barbara J. Smith
Keyword(s):  
Vascular Tissue ◽  
Light And Electron Microscopy ◽  
Hyphal Growth ◽  
Fungal Species ◽  
Colletotrichum Acutatum ◽  
Cortical Tissue ◽  
In Planta ◽  
Strawberry Anthracnose ◽  
Strawberry Cultivar ◽  
Germ Tubes

Ontogeny of the invasion process by Colletotrichum acutatum and C. fragariae was studied on petioles and stolons of the strawberry cultivar Chandler using light and electron microscopy. The invasion of host tissue by each fungal species was similar; however, each invasion event occurred more rapidly with C. fragariae than with C. acutatum. Following cuticular penetration via an appressorium, subsequent steps of invasion involved hyphal growth within the cuticle and within the cell walls of epidermal, subepidermal, and subtending cells. Both species of fungi began invasion with a brief biotrophic phase before entering an extended necrotrophic phase. Acervuli formed once the cortical tissue had been moderately disrupted and began with the development of a stroma just beneath the outer periclinal epidermal walls. Acervuli erupted through the cuticle and released conidia. Invasion of the vascular tissue typically occurred after acervulus maturation and remained minimal. Chitin distribution in walls of C. fragariae was visualized with gold-labeled wheat germ agglutinin. The outer layer of bilayered walls of conidia, germ tubes, and appressoria contained less chitin than unilayered hyphae in planta.

Monoclonal antibodies to isolate-, species-, and genus-specific components on the surface of zoospores and cysts of the fungus Phytophthora cinnamomi

1986 ◽  
Vol 64 (2) ◽  
pp. 311-321 ◽  
Author(s):  
A. R. Hardham ◽  
E. Suzaki ◽  
J. L. Perkin
Keyword(s):  
Monoclonal Antibodies ◽  
Cell Lines ◽  
Fungal Pathogens ◽  
Phytophthora Cinnamomi ◽  
Pathogenic Fungus ◽  
Immunofluorescence Assay ◽  
Pythium Species ◽  
Specific Antigens ◽  
Species Specific ◽  
First Time

Monoclonal antibodies have been raised to components on the surface of glutaraldehyde-fixed zoospores and cysts of an isolate of the pathogenic fungus Phytophthora cinnamomi. Hybridoma supernatants were screened using an immunofluorescence assay, and of 35 cell lines producing antibodies that reacted with the P. cinnamomi cells, 10 have been selected and their specificities examined in detail. The monoclonal antibodies were found to possess a valuable spectrum of taxonomic specificities, and have revealed, for the first time, the presence of isolate-specific antigens on the surface of P. cinnamomi cells. The monoclonal antibodies were tested against six isolates of P. cinnamomi, six species of Phytophthora, and three species of Pythium. In addition to the isolate-specific monoclonal antibodies, species-specific and genus-specific markers which are unambiguous in tests conducted so far have been obtained. The monoclonal antibodies have also revealed the presence of spatially restricted antigens on the surface of the zoospores. Some of these segregated antigens are species-specific and others are more general, occurring in all Phytophthora and Pythium species examined. All of the monoclonal antibodies promise to be of great assistance in investigations of the biology and taxonomy of P. cinnamomi. The methods described should be readily applicable to studies of other fungal pathogens.

scholarly journals Natural History of Cryptosporidiosis in a Birth Cohort in Southern India

2016 ◽  
Vol 64 (3) ◽  
pp. 347-354 ◽  
Author(s):  
Deepthi Kattula ◽  
Nithya Jeyavelu ◽  
Ashok D Prabhakaran ◽  
Prasanna S Premkumar ◽  
Vasanthakumar Velusamy ◽  
...  
Keyword(s):  
Natural History ◽  
Fold Increase ◽  
Cryptosporidium Species ◽  
Southern India ◽  
Host Susceptibility ◽  
Serum Samples ◽  
Cryptosporidium Hominis ◽  
Control And Prevention ◽  
History Of ◽  
Species Specific

Abstract Background Cryptosporidium is a leading cause of moderate to severe childhood diarrhea in resource-poor settings. Understanding the natural history of cryptosporidiosis and the correlates of protection are essential to develop effective and sustainable approaches to disease control and prevention. Methods Children (N = 497) were recruited at birth in semiurban slums in Vellore, India, and followed for 3 years with twice-weekly home visits. Stool samples were collected every 2 weeks and during diarrheal episodes were tested for Cryptosporidium species by polymerase chain reaction (PCR). Serum samples obtained every 6 months were evaluated for seroconversion, defined as a 4-fold increase in immunoglobulin G directed against Cryptosporidium gp15 and/or Cp23 antigens between consecutive sera. Results Of 410 children completing follow-up, 397 (97%) acquired cryptosporidiosis by 3 years of age. PCR identified 1053 episodes of cryptosporidiosis, with an overall incidence of 0.86 infections per child-year by stool and serology. The median age for the first infection was 9 (interquartile range, 4–17) months, indicating early exposure. Although infections were mainly asymptomatic (693 [66%]), Cryptosporidium was identified in 9.4% of diarrheal episodes. The proportion of reinfected children was high (81%) and there was clustering of asymptomatic and symptomatic infections (P < .0001 for both). Protection against infection increased with the order of infection but was only 69% after 4 infections. Cryptosporidium hominis (73.3%) was the predominant Cryptosporidium species, and there was no species-specific protection. Conclusions There is a high burden of endemic cryptosporidiosis in southern India. Clustering of infection is suggestive of host susceptibility. Multiple reinfections conferred some protection against subsequent infection.

Species-specific fertilization can benefit container nursery crop production

2015 ◽  
Vol 95 (2) ◽  
pp. 251-262 ◽  
Author(s):  
Mary Jane Clark ◽  
Youbin Zheng
Keyword(s):  
Crop Production ◽  
Root Zone ◽  
Growth Index ◽  
Dry Weight ◽  
Plant Production ◽  
Application Rates ◽  
Canopy Area ◽  
Weigela Florida ◽  
Species Specific ◽  
Container Nursery

Clark, M. J. and Zheng, Y. 2015. Species-specific fertilization can benefit container nursery crop production. Can. J. Plant Sci. 95: 251–262. To determine the responses of six container-grown shrub species to different controlled-release fertilizer (CRF) application rates, plant growth and root-zone traits were evaluated following fertilization with Polyon® 16–6–13, 5–6 month CRF incorporated at 0.60, 0.89, 1.19, 1.49 and 1.79 kg m−3 N. The six species tested at a southwestern Ontario, Canada, nursery were Cornus stolonifera ‘Flaviramea’ (yellow-twig dogwood), Euonymus alatus ‘Compactus’ (dwarf winged euonymus), Hydrangea paniculata ‘Grandiflora’ (Pee Gee hydrangea), Physocarpus opulifolius ‘Nugget’ (Nugget ninebark), Spiraea japonica ‘Magic Carpet’ (Magic Carpet spirea), Weigela florida ‘Alexandra’ (Wine and Roses weigela). Different species responded differently to the CRF rates applied. For the majority of species at the final harvest, growth index, plant height, canopy area, leaf area and above-ground dry weight were greater in high vs. low CRF rates; however, different species had different optimal CRF application rates or ranges: 1.49 kg m−3 N for Hydrangea and Spiraea, 1.19 kg m−3 N for Weigela, 1.19 to 1.49 kg m−3 N for Cornus and Physocarpus, and ≤0.60 kg m−3 N for Euonymus. Based on these species-specific optimal fertilizer rates or ranges, growers can group plant species with similar fertilizer demands, thereby reducing fertilizer waste and maximizing plant production.

scholarly journals Developing the Pecan Scab Fungus on Susceptible and Resistant Host and Nonhost Leaves

1996 ◽  
Vol 121 (3) ◽  
pp. 350-357 ◽  
Author(s):  
I.E. Yates ◽  
Donnie Maxey ◽  
Seonju Lee ◽  
Darrell Sparks ◽  
C.C. Reilly
Keyword(s):  
Germ Tube ◽  
Fungal Growth ◽  
Host Susceptibility ◽  
Scab Resistance ◽  
Susceptible Host ◽  
Hyphal Development ◽  
Leaf Maturity ◽  
Leaf Surfaces ◽  
Pecan Scab ◽  
Germ Tubes

Germ tube, appressorium, and subcuticular hypha development were analyzed on host and nonhost leaves for Cladosporium caryigenum (Ell. et Lang. Gottwald), the fungus causing scab on pecan [Carya illinoinensis (Wangenh.) C. Koch]. Plant features characterized for supporting fungal growth were genotype, adaxial and abaxial leaf surfaces, and leaf maturity. Germ tubes and appressoria developed on all plant leaves, despite genotype, leaf surface, or maturity. Germ tube frequency on the susceptible host, `Wichita', was lower than on the resistant host, `Elliott', but was not significantly different from the nonhost, tobacco (Nicotiana tabacum L.). Appressoria formed with equal frequency on leaves of both pecan cultivars and tobacco. Adaxial and abaxial leaf surfaces were not different within any given genotype for supporting fungal development. Immature leaves of `Elliott', but not of `Wichita', had a higher frequency of germ tubes and appressoria than mature leaves. Subcuticular hyphal development occurred only on immature leaves of susceptible `Wichita' pecan. Hence, subcuticular hyphal development is a prime candidate for being the fungal stage specific for host susceptibility. Resistance to C. caryigenum infection appears to be expressed at the plant site beneath the cuticle as fungal hyphae did not develop in a resistant pecan genotype or on nonhost leaves. Thus, resistance to the fungus causing pecan scab likely is expressed after both germ tube and appressorium development and operates beneath, not on the surface, of the leaf cuticle. Furthermore, technology developed to make these assessments would be adaptable in pecan breeding programs to screen for scab resistance.

scholarly journals Review of science-based assessments of species vulnerability: Contributions to decision-making for assisted migration

2011 ◽  
Vol 87 (06) ◽  
pp. 745-754 ◽  
Author(s):  
Tannis Beardmore ◽  
Richard Winder
Keyword(s):  
Climate Change ◽  
Forest Tree ◽  
Individual Species ◽  
Assisted Migration ◽  
Forest Species ◽  
Genetic Risk Assessment ◽  
Change Models ◽  
Forest Management Planning ◽  
Species Vulnerability ◽  
Species Specific

Assessing climate change impacts on forest species can significantly assist forest management planning. Recently, many tools have been developed for assessing species-specific vulnerability to climate change. These tools are question-based assessments that consider multiple criteria for individual species; the criteria are related to exposure and sensitivity to climate change. The following tools are discussed in relation to their use in Canada: (1) the NatureServe Climate Change Vulnerability Index; (2) the System for Assessing Vulnerability of Species to Climate Change (SAVS); (3) the Forest Tree Genetic Risk Assessment; (4) the Index for Predicting Tree Species Vulnerability; (5) ecological standards developed for the assisted migration of Torreya taxifolia; and (6) the Seeds of Success Program. These tools can all be applied to different forest species and they vary in such areas as their species-specific evaluation criteria, means for addressing uncertainty, and the integration of climate change models.

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