Pathogenicity of Pythium spp. And Phytopththora drechsleri to Eucalyptus spp

1974 ◽  
Vol 22 (4) ◽  
pp. 661 ◽  
Author(s):  
GC Marks ◽  
FY Kassaby
Keyword(s):  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Pythium Ultimum ◽  
Pythium Species ◽  
Marked Contrast ◽  
Small Juvenile ◽  
Eucalypt Forest ◽  
Stage Of Development ◽  
Eastern Australia ◽  
Phytophthora Drechsleri

A number of Pythium spp, and Phytophthora drechsleri have been associated with Phytophthora cinnamomi in the die-back disease of eucalypts in forests of southern and eastern Australia. Although P. cinnamomi is generally considered to be the most important pathogen causing root rot and die-back, there is some uncertainty whether it is the only pathogen. The pathogenicity of Pythium ultimum, P. irregulare, P. debaryanum, P. vexans, P. mamillatum, three unidentified Pythium species from eucalypt forest soil and Phytophthora drechsleri was compared with that of Phytophthora cinnamomi on juvenile and intermediate-aged seedlings of Eucalyptus sieberi and juvenile seedlings of other eucalypt species. Of the Pythiums, only P. ultimum, P. irregulare and P. debaryanum could kill small juvenile seedlings at the two-leaf stage of development. Neither any of the Pythiums nor Phytophthora drechsleri could kill E. sieberi at the intermediate growth stage. In marked contrast, Phytophthora cinnamomi showed considerable pathogenicity, killing seedlings and saplings with rapidity. The unidentified Pythium spp, from native forests were completely innocuous.

scholarly journals Soilborne Phytophthora and Pythium Diversity From Rhododendron in Propagation, Container, and Field Production Systems of the Pacific Northwest

Plant Disease ◽  
2020 ◽  
Vol 104 (6) ◽  
pp. 1841-1850
Author(s):  
Jerry E. Weiland ◽  
Carolyn. F. Scagel ◽  
Niklaus J. Grünwald ◽  
E. Anne Davis ◽  
Bryan R. Beck ◽  
...  
Keyword(s):  
Disease Control ◽  
Pacific Northwest ◽  
Root Rot ◽  
Production Systems ◽  
Phytophthora Cinnamomi ◽  
Phytophthora Species ◽  
Pythium Species ◽  
Disease Etiology ◽  
The Past ◽  
Field Systems

Rhododendron root rot is a severe disease that causes significant mortality in rhododendrons. Information is needed about the incidence and identity of soilborne Phytophthora and Pythium species causing root rot in Pacific Northwest nurseries in order to better understand the disease etiology and to optimize disease control strategies. The last survey focusing solely on soilborne oomycete pathogens in rhododendron production was conducted in 1974. Since then, advances in pathogen identification have occurred, new species may have been introduced, pathogen communities may have shifted, and little is known about Pythium species affecting this crop. Therefore, a survey of root-infecting Phytophthora and Pythium species was conducted at seven nurseries from 2013 to 2017 to (i) document the incidence of root rot damage at each nursery and stage of production, (ii) identify soilborne oomycetes infecting rhododendron, and (iii) determine whether there are differences in pathogen diversity among nurseries and production systems. Rhododendrons from propagation, container, and field systems were sampled and Phytophthora and Pythium species were isolated from the roots and collar region. Root rot was rarely evident in propagation systems, which were dominated by Pythium species. However, severe root rot was much more common in container and field systems where the genus Phytophthora was also more prevalent, suggesting that Phytophthora species are the primary cause of severe root rot and that most contamination by these pathogens comes in after the propagation stage. In total, 20 Pythium species and 11 Phytophthora species were identified. Pythium cryptoirregulare, Pythium aff. macrosporum, Phytophthora plurivora, and Phytophthora cinnamomi were the most frequently isolated species and the results showed that Phytophthora plurivora has become much more common than in the past. Phytophthora diversity was also greater in field systems than in propagation or container systems. Risks for Phytophthora contamination were commonly observed during the survey and included placement of potting media in direct contact with field soil, the presence of dead plants that could serve as continuous sources of inoculum, and the presence of excess water as a result of poor drainage, overirrigation, or malfunctioning irrigation equipment. In the past, research on disease development and root rot disease control in rhododendron focused almost exclusively on Phytophthora cinnamomi. More research is needed on both of these topics for the other root-infecting species identified in this survey.

scholarly journals Oospore Production in Phytophthora Cinnamomi in the Presence of Trichoderma Koningii

1972 ◽  
Vol 25 (4) ◽  
pp. 861 ◽  
Author(s):  
BH Pratt ◽  
JH Sedgley ◽  
WA Heather ◽  
CJ Shepherd
Keyword(s):  
East Asia ◽  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
South East Asia ◽  
Native Plant ◽  
Native Plant Species ◽  
Root Rot Disease ◽  
Trichoderma Koningii ◽  
Eastern Australia ◽  
Rot Disease

The soil-borne fungus Phytophthora cinnamomi Rands is a particularly impor-tant pathogen in Australia because of its consistent association with root-rot disease of a wide variety of exotic and native plant species. It was thought originally to have been introduced from south-east Asia (Crandall and Gravatt 1967), but evidence recently obtained (Pratt, Heather, and Shepherd, unpublished data), suggests that it may be indigenous to eastern Australia and may have been partly instrumental in determining the distribution of certain susceptible species, particularly Eucalyptu8 spp.

Pythium species associated with root rot complex in winter-grown parsnip and parsley crops in south eastern Australia

2013 ◽  
Vol 42 (4) ◽  
pp. 403-411 ◽  
Author(s):  
J. E. Petkowski ◽  
R. F. de Boer ◽  
S. Norng ◽  
F. Thomson ◽  
E. J. Minchinton
Keyword(s):  
Root Rot ◽  
Pythium Species ◽  
South Eastern ◽  
Eastern Australia ◽  
South Eastern Australia

Phytophthora drechsleri Tucker and Pythium spp. as pathogens of safflower in New South Wales

1973 ◽  
Vol 13 (63) ◽  
pp. 455 ◽  
Author(s):  
G Stovold
Keyword(s):  
Root Rot ◽  
New South ◽  
New South Wales ◽  
Field Capacity ◽  
Pythium Ultimum ◽  
Carthamus Tinctorius ◽  
Pythium Myriotylum ◽  
Pythium Irregulare ◽  
South Wales ◽  
Phytophthora Drechsleri

Pythiaceous fungi associated with a widespread root rot disease of safflower (Carthamus tinctorius) in New South Wales include Phytophthora drechsleri, Pythium myriotylum, Pythium ultimum Pythium irregulare, Pythium acanthicum, and a number of sterile Pythium spp. Pathogenicity of these fungi was tested against safflower seedlings and older plants growing either in soil with moisture content at field capacity or in flooded soil. Phytophthora drechsleri, Pythium myriotylum, Pythium ultimum and Pythiumirregulare caused severe pre-emergence damping off. When safflower plants, three and eight weeks old, were inoculated with each of the fungi, only Phytophthora drechsleriand Pythium myriotylum killed a high proportion of plants. The pathogenicity of Phytophthora drechsleri, Pythium myriotylum, Pythium ultimum, and Pythium irregulare was increased by flooding the soil for ninety hours after inoculation. Phytophthora drechsleri was isolated from naturally infected saffron thistle (Carthamus lanatus). Cross inoculation tests with Phytophthora drechsleri isolates from safflower and saffron thistle showed that both isolates could infect each host. Saffron thistle could be an important alternative host of Phytophthora drechsleri in the field. It is concluded that Phytophthora drechsleri is the major cause of root rot of safflower in New South Wales.

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

2011 ◽  
Vol 101 (2) ◽  
pp. 223-230 ◽  
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.

Identification of Pythium species as pathogens of garlic root rot

2021 ◽  
Author(s):  
Bo Zhang ◽  
Yueli Zhang ◽  
Liguo Ma ◽  
Kai Qi ◽  
Peng Wang ◽  
...  
Keyword(s):  
Root Rot ◽  
Pythium Species

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

Forests ◽  
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.

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

2021 ◽  
Author(s):  
Olumide S. Jeff-Ego ◽  
Andre Drenth ◽  
Bruce Topp ◽  
Juliane Henderson ◽  
Olufemi A. Akinsanmi
Keyword(s):  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Stem Canker

scholarly journals Using Commercial Compost as Control Measures against Cucumber Root-Rot Disease

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Kamel Kamal Sabet ◽  
Magdy Mohamed Saber ◽  
Mohamed Adel-Aziz El-Naggar ◽  
Nehal Samy El-Mougy ◽  
Hatem Mohamed El-Deeb ◽  
...  
Keyword(s):  
Root Rot ◽  
Control Measure ◽  
Disease Incidence ◽  
Pathogenic Fungi ◽  
Pythium Ultimum ◽  
Control Measures ◽  
Infested Soil ◽  
Fungal Isolates ◽  
Cucumber Root

Five commercial composts were evaluated to suppress the root-rot pathogens (Fusarium solani (Mart.) App. and Wr, Pythium ultimum Trow, Rhizoctonia solani Kuhn, and Sclerotium rolfsii Sacc.) of cucumber plants under in vitro and greenhouse conditions. In vitro tests showed that all tested unautoclaved and unfiltrated composts water extracts (CWEs) had inhibitor effect against pathogenic fungi, compared to autoclaved and filtrated ones. Also, the inhibitor effects of 40 bacteria and 15 fungi isolated from composts were tested against the mycelial growth of cucumber root-rot pathogens. Twenty two bacteria and twelve fungal isolates had antagonistic effect against root-rot pathogens. The antagonistic fungal isolates were identified as 6 isolates belong to the genus Aspergillus spp., 5 isolates belong to the genus Penicillium spp. and one isolate belong to the genus Chaetomium spp. Under greenhouse conditions, the obtained results in pot experiment using artificial infested soil with cucumber root-rot pathogens showed that the compost amended soil reduced the percentage of disease incidence, pathogenic fungi population, and improved the cucumber vegetative parameters as shoot length, root length, fresh weight, and dry weight. These results suggested that composts are consequently considered as control measure against cucumber root-rot pathogens.

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