Variation in susceptibility among macadamia genotypes and species to Phytophthora root decay caused by Phytophthora cinnamomi

On lateritic podzolic soils in Western Australia Eucalyptus calophylla is resistant to Phytophthora cinnamomi whereas Eucalyptus marginata is susceptible and eventually killed by the pathogen. On loam soils both eucalypts are resistant. Possible mechanisms for resistance of E. calophylla in lateritic soil and the inhibitory action of loam soils were investigated. Aseptically raised eucalypt seedlings succumbed to infection in liquid culture tubes. The mechanism of infection was compared by light and electron microscopy which showed similar fungal invasion and penetration into roots of both eucalypt species. Vegetative hyphae initially penetrated intercellularly and proliferated rapidly within cortical and stelar tissue. Intracellular invasion of these tissues occurred 48hr after initial infection through dissolution of the host cell wall. Chlamydospores were formed within a number of cortical cells. Unsuberized roots of mature trees produced aseptically showed reactions to invasion similar to those of the eucalypt seedling roots. Suberized roots were not invaded. The addition of small quantities of lateritic soil to sterile sand so as to introduce soil micro-organisms without altering the chemical and physical status of the sand, and subsequent inoculation of the sand with P.cinnamomi, resulted in a reduction of root damage on both eucalypts when compared with seedlings raised in sterile sand. Roots of E.calophylla were less severely damaged than those of E.marginata. The addition of small quantities of loam soil significantly reduced root damage in seedlings of both species. These results parallel both pot experiments and field observations, and suggest that microorganisms of the rhizosphere may be an important factor in the resistance of E.calophylla to infection, and in the inhibitory effect of loam soil on P.cinnamomi.

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Differential responses of needle and branch order-based root decay to nitrogen addition: dominant effects of acid-unhydrolyzable residue and microbial enzymes

Plant and Soil ◽

10.1007/s11104-015-2517-2 ◽

2015 ◽

Vol 394 (1-2) ◽

pp. 315-327 ◽

Cited By ~ 10

Author(s):

Liang Kou ◽

Weiwei Chen ◽

Xinyu Zhang ◽

Wenlong Gao ◽

Hao Yang ◽

...

Keyword(s):

Nitrogen Addition ◽

Microbial Enzymes ◽

Branch Order ◽

Root Decay ◽

Differential Responses

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Cellulase Activity as a Mechanism for Suppression of Phytophthora Root Rot in Mulches

Phytopathology ◽

10.1094/phyto-04-10-0125 ◽

2011 ◽

Vol 101 (2) ◽

pp. 223-230 ◽

Cited By ~ 16

Author(s):

Brantlee Spakes Richter ◽

Kelly Ivors ◽

Wei Shi ◽

D. M. Benson

Keyword(s):

Root Rot ◽

Phytophthora Cinnamomi ◽

Cellulase Activity ◽

Enzyme Concentration ◽

Disease Suppression ◽

In Vitro Assays ◽

Infested Soil ◽

Phytophthora Root Rot ◽

Standard Curve

Wood-based mulches are used in avocado production and are being tested on Fraser fir for reduction of Phytophthora root rot, caused by Phytophthora cinnamomi. Research with avocado has suggested a role of microbial cellulase enzymes in pathogen suppression through effects on the cellulosic cell walls of Phytophthora. This work was conducted to determine whether cellulase activity could account for disease suppression in mulch systems. A standard curve was developed to correlate cellulase activity in mulches with concentrations of a cellulase product. Based on this curve, cellulase activity in mulch samples was equivalent to a cellulase enzyme concentration of 25 U ml–1 or greater of product. Sustained exposure of P. cinnamomi to cellulase at 10 to 50 U ml–1 significantly reduced sporangia production, but biomass was only reduced with concentrations over 100 U ml–1. In a lupine bioassay, cellulase was applied to infested soil at 100 or 1,000 U ml–1 with three timings. Cellulase activity diminished by 47% between 1 and 15 days after application. Cellulase applied at 100 U ml–1 2 weeks before planting yielded activity of 20.08 μmol glucose equivalents per gram of soil water (GE g–1 aq) at planting, a level equivalent to mulch samples. Cellulase activity at planting ranged from 3.35 to 48.67 μmol GE g–1 aq, but no treatment significantly affected disease progress. Based on in vitro assays, cellulase activity in mulch was sufficient to impair sporangia production of P. cinnamomi, but not always sufficient to impact vegetative biomass.

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Disentangling the interactive effects of climate change and Phytophthora cinnamomi on coexisting Mediterranean tree species

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2020.108295 ◽

2021 ◽

Vol 298-299 ◽

pp. 108295

Author(s):

María Socorro Serrano ◽

Francisco José Pérez ◽

Lorena Gómez-Aparicio

Keyword(s):

Climate Change ◽

Tree Species ◽

Phytophthora Cinnamomi ◽

Interactive Effects

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Phytophthora mediterranea sp. nov., a New Species Closely Related to Phytophthora cinnamomi from Nursery Plants of Myrtus communis in Italy

Forests ◽

10.3390/f12060682 ◽

2021 ◽

Vol 12 (6) ◽

pp. 682

Author(s):

Carlo Bregant ◽

Antonio A. Mulas ◽

Giovanni Rossetto ◽

Antonio Deidda ◽

Lucia Maddau ◽

...

Keyword(s):

New Species ◽

Root Rot ◽

Phytophthora Cinnamomi ◽

Colony Growth ◽

Phytophthora Species ◽

Maximum Temperature ◽

Pathogenicity Test ◽

Forest Nurseries ◽

Collar And Root Rot ◽

A New Species

Monitoring surveys of Phytophthora related diseases in four forest nurseries in Italy revealed the occurrence of fourteen Phytophthora species to be associated with collar and root rot on fourteen plants typical of Mediterranean and alpine regions. In addition, a multilocus phylogeny analysis based on nuclear ITS and ß-tubulin and mitochondrial cox1 sequences, as well as micromorphological features, supported the description of a new species belonging to the phylogenetic clade 7c, Phytophthora mediterranea sp. nov. Phytophthora mediterranea was shown to be associated with collar and root rot symptoms on myrtle seedlings. Phylogenetically, P. mediterranea is closely related to P. cinnamomi but the two species differ in 87 nucleotides in the three studied DNA regions. Morphologically P. mediterranea can be easily distinguished from P. cinnamomi on the basis of its smaller sporangia, colony growth pattern and higher optimum and maximum temperature values. Data from the pathogenicity test showed that P. mediterranea has the potential to threaten the native Mediterranean maquis vegetation. Finally, the discovery of P. cinnamomi in alpine nurseries, confirms the progressive expansion of this species towards cold environments, probably driven by climate change.

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The influence of time, soil moisture and exogenous factors on the survival potential of oospores and chlamydospores of Phytophthora cinnamomi

Forest Pathology ◽

10.1111/efp.12637 ◽

2020 ◽

Vol 51 (1) ◽

Author(s):

Jamba Gyeltshen ◽

William A. Dunstan ◽

Andrew H. Grigg ◽

Treena I. Burgess ◽

Giles E. St. J. Hardy

Keyword(s):

Soil Moisture ◽

Phytophthora Cinnamomi ◽

Exogenous Factors ◽

Survival Potential

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Allelopathic Effects of Three Herb Species on Phytophthora cinnamomi, a Pathogen Causing Severe Oak Decline in Mediterranean Wood Pastures

Forests ◽

10.3390/f12030285 ◽

2021 ◽

Vol 12 (3) ◽

pp. 285

Author(s):

Manuela Rodríguez-Romero ◽

Belén Godoy-Cancho ◽

Isabel M. Calha ◽

José António Passarinho ◽

Ana Cristina Moreira

Keyword(s):

Phytophthora Cinnamomi ◽

Raphanus Raphanistrum ◽

Inhibitory Capacity ◽

Pathogen Suppression ◽

Pathogen Populations ◽

Defensive Chemical ◽

Chemical Response ◽

Herb Species

The ability of three herbaceous plants (Diplotaxis tenuifolia (L.) DC., Eruca vesicaria L. and Raphanus raphanistrum L.) from Iberian wood pastures to reduce Phytophthora cinnamomi Rands pathogen populations through allelopathic relationships is studied. The inhibitory capacity of their aqueous root extracts (AREs) on mycelial growth and production of P. cinnamomi reproductive structures is analysed in vitro. In addition, Quercus seedlings were grown in infested by P. cinnamomi-soils and with the presence or absence of allelopathic and susceptible herb species to the pathogen to assess the defensive chemical response of Quercus seedlings through their leaf phenolic compounds. Results show a strong inhibitory capacity of AREs on P. cinnamomi activity in vitro and a protective effect of these herb species on Quercus plants against P. cinnamomi in vivo. D. tenuifolia would be especially suited for biological control in the pathogen suppression.

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Protective Antifungal Activity of Plantago major Extract Against the Phytopathogenic Fungi Phytophthora cinnamomi, Diplodia corticola and Colletotrichum Species

Proceedings ◽

10.3390/foods_2020-07678 ◽

2020 ◽

Vol 70 (1) ◽

pp. 94

Author(s):

Cláudia Ferreira ◽

Rui Oliveira

Keyword(s):

Antifungal Activity ◽

Secondary Metabolites ◽

Plant Extracts ◽

Phytophthora Cinnamomi ◽

Fungal Infections ◽

Petri Dish ◽

Phytopathogenic Fungi ◽

Colletotrichum Acutatum ◽

Lower Probability ◽

Plantago Major

Synthetic fungicides for crops protection raise environmental and human concerns due to accumulation in edible vegetables, showing significant toxicity to humans, and in soil, groundwater and rivers, affecting ecological balance. In addition, they are prone to the development of resistant strains because of the single target-based mechanism of action. Plant extracts provide attractive alternatives, as they constitute a rich source of biodegradable secondary metabolites, such as phenols, flavonoids and saponins, which have multiple modes of antifungal action and a lower probability of the development of resistant fungi. This work has the objective of identifying plant extracts with antifungal activity, aiming to contribute to food safety and sustainable agricultural practices. We selected a saponin-containing plant, Plantago major, and extracted secondary metabolites with 50% (v/v) ethanol, dried by evaporation, and dissolved in water. For antifungal activity, the phytopathogenic fungi Colletotrichum acutatum, Colletotrichum gloeosporioides, Colletotrichum godetiae, Colletotrichum nymphaeae, Diplodia corticola and Phytophthora cinnamomi were selected because they affect fruits and vegetables, such as strawberry, almond, apple, avocado, blueberry and chestnut trees. The aqueous extract was incorporated into PDA medium at different concentrations and mycelial discs were placed in the center of each Petri dish. Growth was measured as the radial mycelial growth at 3, 6, and 9 days incubation at 25 °C in the dark. The maximum growth inhibition (32.2%) was obtained against P. cinnamomi with 2000 µg/mL extract followed by C. gloeosporioides (25.7%) on the sixth day and by C. godetiae and C. nymphaeae (21.1%) on the ninth day. Results show that P. major presents antifungal activity in all phytopathogenic fungi tested and the extract can be used to protect important crops, by inhibiting the development of fungal infections and promoting food security and a sustainable agriculture.

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Variability and inheritance in macadamia progenies to Phytophthora cinnamomi and P. multivora the causal agents of root rot and stem canker

Plant and Soil ◽

10.1007/s11104-021-05064-y ◽

2021 ◽

Author(s):

Olumide S. Jeff-Ego ◽

Andre Drenth ◽

Bruce Topp ◽

Juliane Henderson ◽

Olufemi A. Akinsanmi

Keyword(s):

Root Rot ◽

Phytophthora Cinnamomi ◽

Stem Canker

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Glycoconjugates on the surface of spores of the pathogenic fungus Phytophthora cinnamomi studied using fluorescence and electron microscopy and flow cytometry

Canadian Journal of Microbiology ◽

10.1139/m90-032 ◽

1990 ◽

Vol 36 (3) ◽

pp. 183-192 ◽

Cited By ~ 22

Author(s):

A. R. Hardham ◽

E. Suzaki

Keyword(s):

Flow Cytometry ◽

Plasma Membrane ◽

Cell Surface ◽

Phytophthora Cinnamomi ◽

Pathogenic Fungus ◽

Fluorescein Isothiocyanate ◽

Pathogenic Fungi ◽

Surface Flow ◽

Soybean Agglutinin ◽

Binding Material

Glycoconjugates on the surface of zoospores and cysts of the pathogenic fungus Phytophthora cinnamomi have been studied using fluorescein isothiocyanate labelled lectins for fluorescence microscopy and flow cytometry, and ferritin- and gold-labelled lectins for ultrastructural analysis. Of the five lectins used, only concanavalin A (ConA) binds to the surface of the zoospores, including the flagella and water expulsion vacuole. This suggests that of accessible saccharides, glucosyl or mannosyl residues predominate on the outer surface of the zoospore plasma membrane. Early in encystment, a system of flat disc-like cisternae, which underlie the zoospore plasma membrane, vesiculate. These and other small peripheral vesicles quickly disappear. After the induction of encystment, ConA is no longer localised close to the plasma membrane but binds to material loosely associated with the cell surface. Quantitative measurements by flow cytometry indicate that the ConA-binding material is gradually lost from the cell surface. The cyst wall is weakly labelled, but the site of germ tube emergence stains intensely. During the first 2 min after the induction of encystment, material that binds soybean agglutinin, Helix pommatia agglutinin, and peanut agglutinin appears on the surface of the fungal cells. The distribution of this material, rich in galactosyl or N-acetyl-D-galactosaminosyl residues, is initially patchy, but by 5 min the material evenly coats most of the cell surface. Labelling of zoospores in which intracellular sites are accessible indicates that the soybean agglutinin binding material is stored in vesicles that lie beneath the plasma membrane. Quantitation of soybean agglutinin labelling shows that maximum binding occurs 2–3 min after the induction of encystment. Key words: cell surface, flow cytometry, lectins, pathogenic fungi, Phytophthora cinnamomi.

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