A Forest Soil Suppressive to Phytophthora cinnamomi and Conducive to Phytophthora cryptogea. II. Suppression of Sporulation.

1982 ◽  
Vol 30 (1) ◽  
pp. 27 ◽  
Author(s):  
DM Halsall
Keyword(s):  
Microbial Population ◽  
Phytophthora Cinnamomi ◽  
Soil Extract ◽  
Aerobic Bacteria ◽  
Suppressive Soil ◽  
Eucalypt Forest ◽  
Inhibitory Compounds ◽  
Soluble Components ◽  
Conducive Soil ◽  
Suppressive Action

Extracts of soil from a wet sclerophyll eucalypt forest suppressed the formation of Phytophthora cinnamomi sporangia but facilitated production of P. cryptogea sporangia and zoospores. This suppressive action was shown to be associated in part with the microbial components of the extract and in part with the soluble components. The microbial population of the suppressive soil contained significantly greater numbers of actinomycetes than the conducive soil tested at the same time. All Streptomyes isolates from the suppressive soil were shown to be antagonistic to certain of the aerobic bacteria from the same soil and to directly inhibit mycelial growth of P. cinnamomi. The soluble component of the soil extract inhibited growth of P. cinnamomi to a greater extent than P. Cryptogea. Interactions between soil microorganisms and inhibitory compounds in the soil are considered to be the cause of the suppressive action of the soil against P. cinnamomi whilst facilitating sporulation of P. Cryptogea.

A Forest Soil Suppressive to Phytophthora cinnamomi and Conducive to Phytophthora cryptogea. I. Survival, Germination and Infectivity of Mycelium and Chlamydospores.

1982 ◽  
Vol 30 (1) ◽  
pp. 11 ◽  
Author(s):  
DM Halsall
Keyword(s):  
Forest Soil ◽  
Recovery Rate ◽  
Phytophthora Cinnamomi ◽  
Field Trials ◽  
Chemical Characteristics ◽  
Subsequent Recovery ◽  
Suppressive Soil ◽  
Phytophthora Cryptogea ◽  
Physical And Chemical ◽  
Conducive Soil

The physical and chemical characteristics of a forest soil suppressive to P. cinnamomi are compared with those of other, previously described, suppressive soils. Recovery of P. cinnamomi chlamydospores from the suppressive soil was reduced to 51% of recovery from condilcive soil when the chlamydospores were mixed through the soil immediately prior to sampling. The subsequent recovery rate decreased more rapidly in the suppressive soil than in the conducive soil. Germination of chlamydospores by the formation of a terminal sporangium and zoospores was inhibited in the suppressive soil. Degeneration of mycelium was more rapid in the suppressive than in the conducive soil. Glasshouse tests showed infection of seedlings growing in the suppressive soil could occur when a zoospore inoculum was used. Infection was greatly reduced when a chlamydospore inoculum was used. Field trials in Tallaganda State Forest, N.S.W., indicated that P. cinnamomi introduced into this habitat rarely caused infection and was unlikely to spread.

scholarly journals In Situ Production of Zoospores by Five Species of Phytophthora in Aqueous Environments for Use as Inocula

Plant Disease ◽  
2014 ◽  
Vol 98 (4) ◽  
pp. 551-558 ◽  
Author(s):  
G. A. Ridge ◽  
S. N. Jeffers ◽  
W. C. Bridges ◽  
S. A. White
Keyword(s):  
Laboratory Experiment ◽  
Constructed Wetlands ◽  
Aquatic Plant ◽  
Phytophthora Cinnamomi ◽  
Soil Extract ◽  
Greenhouse Experiment ◽  
Zoospore Release ◽  
Aqueous Environments ◽  
Over Time

The goal of this study was to develop a procedure that could be used to evaluate the potential susceptibility of aquatic plants used in constructed wetlands to species of Phytophthora commonly found in nurseries. V8 agar plugs from actively growing cultures of three or four isolates of Phytophthora cinnamomi, P. citrophthora, P. cryptogea, P. nicotianae, and P. palmivora were used to produce inocula. In a laboratory experiment, plugs were placed in plastic cups and covered with 1.5% nonsterile soil extract solution (SES) for 29 days, and zoospore presence and activity in the solution were monitored at 2- or 3-day intervals with a rhododendron leaf disk baiting bioassay. In a greenhouse experiment, plugs of each species of Phytophthora were placed in plastic pots and covered with either SES or Milli-Q water for 13 days during both summer and winter months, and zoospore presence in the solutions were monitored at 3-day intervals with the baiting bioassay and by filtration. Zoospores were present in solutions throughout the 29-day and 13-day experimental periods but consistency of zoospore release varied by species. In the laboratory experiment, colonization of leaf baits decreased over time for some species and often varied among isolates within a species. In the greenhouse experiment, bait colonization decreased over time in both summer and winter, varied among species of Phytophthora in the winter, and was better in Milli-Q water. Zoospore densities in solutions were greater in the summer than in the winter. Decreased zoospore activities for some species of Phytophthora were associated with prolonged temperatures below 13 or above 30°C in the greenhouse. Zoospores from plugs were released consistently in aqueous solutions for at least 13 days. This procedure can be used to provide in situ inocula for the five species of Phytophthora used in this study so that aquatic plant species can be evaluated for potential susceptibility.

THE EFFECT OF RESIDUAL FERTILIZER COPPER ON AMMONIFICATION, NITRIFICATION AND PROTEOLYTIC POPULATION IN SOME ORGANIC SOILS

1981 ◽  
Vol 61 (2) ◽  
pp. 445-450 ◽  
Author(s):  
S. P. MATHUR ◽  
C. M. PRESTON
Keyword(s):  
Soil Enzymes ◽  
Microbial Population ◽  
Soil Extract ◽  
The Other ◽  
Toxic Effects ◽  
Organic Soils ◽  
Soil Microbial ◽  
Other Hand ◽  
Soil Microbial Population ◽  
Extracellular Proteolysis

As a part of attempts at examining the suitability of using moderate amounts of Cu for mitigating the undesirably fast decomposition and subsidence of some organic soils, this investigation revealed that both total and DTPA-TEA-extractable Cu contents of 14 samples of cultivated organic soils correlated negatively with the total microbial population counted on soil extract-acitidione-gelatin agar plates and positively with the percentage of that population capable of extracellular proteolysis. On the other hand, the concentrations of both total and extractable Cu did not correlate with either the total number of proteolytic organisms counted, or the capacities of the soils for ammonification and nitrification. The results are, therefore, in accord with the belief that Cu curtails the decomposition of organic soils primarily through inactivation of accumulated soil enzymes, but not through direct toxic effects on the general soil microbial population.

scholarly journals Microbial Communities Associated with Potato Common Scab-Suppressive Soil Determined by Pyrosequencing Analyses

Plant Disease ◽  
2012 ◽  
Vol 96 (5) ◽  
pp. 718-725 ◽  
Author(s):  
Noah Rosenzweig ◽  
James M. Tiedje ◽  
John F. Quensen ◽  
Qingxiao Meng ◽  
Jianjun J. Hao
Keyword(s):  
Microbial Communities ◽  
Common Scab ◽  
Disease Suppression ◽  
Rrna Gene ◽  
Suppressive Soil ◽  
Streptomyces Spp ◽  
Potato Common Scab ◽  
Order Of Magnitude ◽  
Disease Suppressive Soil ◽  
Conducive Soil

Potato common scab, caused by Streptomyces spp., is an annual production problem for potato growers, and not effectively controlled by current methods. A field with naturally occurring common scab suppression has been identified in Michigan, and confirmed to have a biological basis for this disease suppression. This field and an adjacent scab nursery conducive to disease were studied using pyrosequencing to compare the two microbial communities. Total DNA was extracted from both the disease-conducive and -suppressive soils. A phylogenetically taxon-informative region of the 16S rRNA gene was used to establish operational taxonomic units (OTUs) to characterize bacterial community richness and diversity. In total, 1,124 OTUs were detected and 565 OTUs (10% dissimilarity) were identified in disease-conducive soil and 859 in disease-suppressive soil, including 300 shared both between sites. Common phyla based on relative sequence abundance were Acidobacteria, Proteobacteria, and Firmicutes. Sequences of Lysobacter were found in significantly higher numbers in the disease-suppressive soil, as were sequences of group 4 and group 6 Acidobacteria. The relative abundance of sequences identified as the genus Bacillus was significantly higher by an order of magnitude in the disease-conducive soil.

scholarly journals (170) Reduction of Natural Microbial Population with Antimicrobial Agents and Subsequent Washing Treatments of Fresh-cut Vegetables

HortScience ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 1081D-1081
Author(s):  
Hidemi Izumi ◽  
Takeshi Yamashita ◽  
Maki Inada
Keyword(s):  
Water Treatment ◽  
Ferulic Acid ◽  
Fumaric Acid ◽  
Antimicrobial Agents ◽  
Microbial Population ◽  
Aerobic Bacteria ◽  
Minimum Concentration ◽  
Electrolyzed Water ◽  
Acid Agent ◽  
Fresh Cut

Ferulic acid agent (2% of ferulic acid), fumaric acid agent (20% of fumaric acid), mustard extract agent (10% of allyl isothiocyanate), and calcined calcium agent (91% of calcium) were assessed for reduction of endogenous microbial population on fresh-cut lettuce, cabbage, and cucumber in the preliminary study. In seeking effective minimum concentration, a 0.5% ferulic acid agent or 1.0% fumaric acid agent applied on lettuce, 0.1% mustard extract agent on cabbage, and 0.05% calcined calcium agent on cucumber reduced mesophilic aerobic bacteria (MAB) and coliform group (coliforms) by about 0.5 to 1.5 logs relative to water-dipped control. The efficacy of these antimicrobial agents with subsequent washing treatments with electrolyzed water (13 ppm of available chlorine) or ozonated water (5 ppm of ozone) on endogenous microorganism were evaluated with fresh-cut vegetables stored in MA package for 4 days at 10 °C. With lettuce, the fumaric acid agent followed by electrolyzed water treatment was the most effective in reducing counts of MAB, coliforms, and psychrotrophic aerobic bacteria (PAB) for the first 2 days of storage. This treatment eliminated gram-positive bacteria such as the genus Curtobacterium and gram-negative bacteria such as the genus Stenotrophomonas. With cucumber, fumaric acid agent or calcined calcium agent with sequential washing with electrolyzed water reduced counts of MAB, coliforms, PAB and lactic acid bacteria during 4 days of storage, with the reduction being greater with fumaric acid agent than with calcined calcium agent. With cabbage, the combinations of the agents and washing treatments had no pronounced effect when compared with water treatment.

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.

Influence of Isolation Method on Growth Rate Characteristics of Populations of Phytophthora cinnamomi

1977 ◽  
Vol 25 (5) ◽  
pp. 477 ◽  
Author(s):  
CJ Shepherd ◽  
RI Forrester
Keyword(s):  
Growth Rate ◽  
Phytophthora Cinnamomi ◽  
Isolation Method ◽  
Direct Plating ◽  
Eucalypt Forest ◽  
North Eastern

Direct plating and baiting methods were used to obtain 266 isolates of Phytophthova cinnamomi from eucalypt forest in north-eastern Victoria. Isolates derived by baiting grew faster than those from plating. Single zoospore progeny showed that many of those obtained by direct plating were probably heterocaryotic for determinants of growth rate, while those obtained by baiting exhibited significantly less variance among single zoospore progenies.

scholarly journals First Report of Phytophthora cinnamomi on Quercus laurifolia

Plant Disease ◽  
2002 ◽  
Vol 86 (4) ◽  
pp. 441-441 ◽  
Author(s):  
A. K. Wood ◽  
F. H. Tainter
Keyword(s):  
Phytophthora Cinnamomi ◽  
Soil Extract ◽  
Selective Medium ◽  
Phytophthora Species ◽  
Soil Samples ◽  
Tissue Samples ◽  
First Report ◽  
Central Florida ◽  
Oak Trees ◽  
Length Width

In May 2001, bleeding cankers were observed on several laurel oak (Quercus laurifolia) trees in central Florida. Affected trees had chlorotic leaves, sparse canopies, and little new growth. Multiple cankers were present on the trunk and extended from the soil line up to approximately 5 m. Each canker had a reddish to dark brown or black exudate. From two of the infected trees, tissue samples were taken from beneath the bark around the edge of an actively growing lesion and transferred directly to Phytophthora-selective medium (1), and three soil cores (2 cm in diameter, 20 cm deep) were collected from the base of each tree. A baiting bioassay (with camellia leaf disks and shore juniper and eastern hemlock needles as baits) was used to assay fresh composite soil samples for Phytophthora species (1). P. cinnamomi was recovered from both tissue and soil samples (2). Mycelia were coralloid with abundant hyphal swellings. Sporangia were produced in 1.5% nonsterilized soil extract solution. Sporangia were ovoid to ellipsoid in shape and nonpapillate. Average sporangium size was 72 × 45 μm (length × width). To our knowledge, this is the first report of P. cinnamomi on laurel oak trees. References: (1) A. J. Ferguson and S. N. Jeffers. Plant Dis. 83:1129, 1999. (2) G. M. Waterhouse. Key to the species of Phytophthora de Bary. Mycol. Pap. 92. CMI. Kew, UK, 1963.

scholarly journals Phenolic Acid-Degrading Consortia Increase Fusarium Wilt Disease Resistance of Chrysanthemum

Agronomy ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 385
Author(s):  
Cheng Zhou ◽  
Zhongyou Ma ◽  
Xiaoming Lu ◽  
Lin Zhu ◽  
Jianfei Wang
Keyword(s):  
Microbial Community ◽  
Fusarium Wilt ◽  
Wilt Disease ◽  
Disease Suppression ◽  
Suppressive Soil ◽  
Soil Borne Pathogens ◽  
Fusarium Wilt Disease ◽  
Pseudomonas Species ◽  
Conducive Soil

Soil microbial community changes imposed by the cumulative effects of root-secreted phenolic acids (PAs) promote soil-borne pathogen establishment and invasion under monoculture systems, but the disease-suppressive soil often exhibits less soil-borne pathogens compared with the conducive soil. So far, it remains poorly understood whether soil disease suppressiveness is associated with the alleviated negative effects of PAs, involving microbial degradation. Here, the long-term monoculture particularly shaped the rhizosphere microbial community, for example by the enrichment of beneficial Pseudomonas species in the suppressive soil and thus enhanced disease-suppressive capacity, however this was not observed for the conducive soil. In vitro PA-degradation assays revealed that the antagonistic Pseudomonas species, together with the Xanthomonas and Rhizobium species, significantly increased the efficiency of PA degradation compared to single species, at least partially explaining how the suppressive soil accumulated lower PA levels than the conducive soil. Pot experiments further showed that this consortium harboring the antagonistic Pseudomonas species can not only lower PA accumulation in the 15-year conducive soils, but also confer stronger Fusarium wilt disease suppression compared with a single inoculum with the antagonistic bacteria. Our findings demonstrated that understanding microbial community functions, beyond the single direct antagonism, facilitated the construction of active consortia for preventing soil-borne pathogens under intensive monoculture.

Behaviour of Phytophthora cinnamomi in soils suppressive and conducive to root rot

1974 ◽  
Vol 25 (1) ◽  
pp. 121 ◽  
Author(s):  
P Broadbent ◽  
KF Baker
Keyword(s):  
Organic Matter ◽  
Forest Soil ◽  
Root Rot ◽  
Rain Forest ◽  
Phytophthora Cinnamomi ◽  
Nutrient Level ◽  
Soil Leachate ◽  
Suppressive Soil ◽  
Isolation Frequency ◽  
Calcium And Magnesium

Suppression of root rot in avocados caused by Phytophthora cinnamomi was demonstrated in soil from a grove at Tamborine Mt., Queensland. The addition of P. cinnamomi inoculum in amounts sufficient to cause severe root rot of plants in other soils, untreated or steam-air treated at 60°C for 30 min, produced little or no damage in the suppressive soil. Suppressive soil was found to have higher populations of bacteria and actinomycetes than soils conducive to root rot. Few sporangia were formed by P. cinnamomi and P. citrophthora in suppressive soil or soil leachate. The suppression of sporangium formation was found to be microbial and not related to the nutrient level of the soil leachate. Mycelium of P. cinnamomi grew through untreated conducive soils, but developed poorly in untreated suppressive soils. The fungus grew readily through all soils steam-air treated at 49, 60 and 100�C for 30 min. After 6 weeks the isolation frequency of P. cinnamomi had declined in the suppressive soil treated at 49 or 60°C for 30 min. Exchangeable calcium and magnesium, nitrogen, and organic matter were higher in soils suppressive to root rot than in conducive soils. Rain-forest soil, where the pathogen is not damaging, was comparable in this respect to the suppressive soil.

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