Effect of Phytophthora cinnamomi on Microbial Populations Associated With the Roots of Forest Flora

1978 ◽  
Vol 26 (2) ◽  
pp. 153 ◽  
Author(s):  
G Weste ◽  
K Vithanage
Keyword(s):  
Phytophthora Cinnamomi ◽  
Severe Disease ◽  
Plant Cover ◽  
Microbial Populations ◽  
Aerobic Bacteria ◽  
Winter Period ◽  
Forest Communities ◽  
Seasonal Periodicity ◽  
Soil Rhizosphere ◽  
Microbial Numbers

The effect of Phytophthora cinnamomi Rands on the microbial populations associated with plant roots of three forest communities was investigated by the dilution plate method. Rhizosphere and rhizoplane populations for susceptible and tolerant hosts and soil microflora were compared for diseased and unaffected areas. Populations of P. cinnamomi were determined concurrently from the same root and soil material. Samples were collected every three months over a 2-year period from sites for which rainfall, soil water potentials and soil temperature were continuously recorded. Independently of the pathogen, microbial numbers from soil, rhizosphere and rhizoplane from the dry shrubby sclerophyll forest of the Brisbane Ranges were significantly lower than those from the savannah woodlands of Wilson's Promontory and one-tenth of those from wetter sclerophyll forests of Narbethong. Microbial populations from soil and roots of the three forest communities exhibited statistically significant seasonal periodicity with maxima in the autumn-winter period and minima in the spring-summer seasons. This contrasts with P. cinnamomi populations, which decreased almost to zero in winter and became maximal in spring-summer. The susceptible roots examined were associated with smaller populations of microorganisms, particularly aerobic bacteria and aerobic sporing bacteria in both rhizosphere and rhizoplane compared with tolerant roots. Disease due to P. cinnamomi did not affect the relative microbial numbers occurring in soil, rhizosphere and rhizoplane, but was always associated with a reduction in numbers of actinomycetes on all sites. Severe disease in the Brisbane Ranges was associated with a significant increase in total microorganisms, particularly aerobic bacteria, in the rhizoplane and rhizosphere of both susceptible and tolerant plants, coincident with the production of decayed and dead root tissue. Anaerobic bacteria increased and actinomycetes decreased in number from all rhizospheres sampled from diseased sites. Finally in areas of severe disease in the Brisbane Ranges there was a subsequent highly significant reduction in numbers of soil microorganisms associated with a decrease of plant cover.

Microbial populations of three forest soils: seasonal variations and changes associated with Phytophthora cinnamomi

1977 ◽  
Vol 25 (4) ◽  
pp. 377 ◽  
Author(s):  
G Weste ◽  
K. Vithanage
Keyword(s):  
Forest Soils ◽  
Phytophthora Cinnamomi ◽  
Severe Disease ◽  
Organic Content ◽  
Microbial Populations ◽  
Garden Soil ◽  
Soil Temperatures ◽  
Disease Extension ◽  
Pathogen Populations ◽  
Soil Microbial Population

Microbial populations of three forest soils were assayed by a dilution plate procedure and compared with garden soil. The forest soils were selected from areas subjected to die-back disease caused by Phytophthora cinnamomi Rands, and were from sites for which pathogen populations, soil temperatures, rainfall and soil water potentials were concurrently recorded. Forest soils showed low microbial populations compared with garden soil. This was associated with low organic content, low nitrogen status and poor water-holding capacity. Areas with severe disease and rapid disease extension had a small soil microbial population, particuarly of actinomycetes, compared with soil from areas with moderate disease and slow disease extension. Microbial populations were lowest in spring and autumn when P. cinnamomi was most active, and zoospore production, dispersal and infection was maximal. Microbial populations of forest soil were reduced following die-back; and the reduction of disease was highly significant (P < 0.01) for the Brisbane Ranges where plant mortality was high and the percentage of bare ground increased.

UV Irradiation of Shell Eggs: Effect on Populations of Aerobes, Molds, and Inoculated Salmonella typhimurium

1997 ◽  
Vol 60 (6) ◽  
pp. 639-643 ◽  
Author(s):  
FUENG-LIN KUO ◽  
JOHN B. CAREY ◽  
STEVEN C. RICKE
Keyword(s):  
Salmonella Typhimurium ◽  
Uv Radiation ◽  
Uv Light ◽  
The Other ◽  
Uv Exposure ◽  
Microbial Populations ◽  
Aerobic Bacteria ◽  
Fluorescent Light ◽  
Uv Treatment ◽  
Shell Eggs

The effects were investigated of 254-nm UV radiation on populations of Salmonella typhimurium, aerobes, and molds on the shells of eggs. In the first experiment, the CFU of attached S. typhimurium cells on unwashed clean shell eggs were determined after 0, 1, 3, 5, and 7 min of UV treatment (620 μW/cm2) on both ends of the egg. All UV treatments significantly reduced S. typhimurium CFU (P &lt; .01). UVtreatment (620 μW/cm2) in 1-min alternating light and dark cycles for 5 min (three light and two dark) was compared to 0, 3, and 5 min of UV treatment. No significant differences in microbial populations were observed among light and dark cycles and the other UV treatments. In a subsequent experiment, the same UV treatments were utilized to evaluate photoreactivation. After UV exposure, eggs were exposed to 1 h of fluorescent light or I h of darkness or cultured immediately. S. typhimurium CFU were significantly (P &lt; .01) reduced by the UV treatments. However, no significant differences between microbial populations exposed to UV treatment and UV radiation plus photoreactivation were detected. For studies of aerobic bacteria and molds, different UV treatment times (0, 15, and 30 min) at the intensity of 620 μW/cm2 and different intensities (620, 1350, and 1720 μW/cm2) for 15 min were evaluated. Mold CFU per egg were either 0 or 1 for all UV treatments and a 99% reduction of CFU of aerobic bacteria per egg were observed for all UV treatments. It appears from these studies that UV light can significantly reduce populations of S. typhimurium, aerobes, and molds on shell eggs.

Effects of potassium azide on soil microbial populations and soil enzymatic activities

1975 ◽  
Vol 21 (4) ◽  
pp. 565-570 ◽  
Author(s):  
W. D. Kelley ◽  
R. Rodriguez-Kabana
Keyword(s):  
Soil Enzyme ◽  
Soil Microflora ◽  
Microbial Populations ◽  
Bacterial Populations ◽  
Soil Microbial ◽  
Fungal Populations ◽  
Potassium Azide ◽  
Time Changes ◽  
Bacteria And Fungi ◽  
Microbial Numbers

Preplant applications of potassium azide (KN3) to pine nursery beds were evaluated for effect on the soil microflora and on soil enzyme activity where either plastic-sealing or water-sealing techniques were used. Two weeks after incorporation of azide (0–224 kg/ha), soil samplings revealed reduced populations of bacteria and fungi and a corresponding decline in invertase and amylase activities. These effects were proportionate to the amount of azide used and were more pronounced in plastic-sealed plots. Phosphatase activity was little affected. Five weeks after azide application, bacterial populations were higher in treated plots than in controls. Greater numbers of bacteria were recorded from plastic-sealed plots and highest populations coincided with plots receiving the highest rates of azide, regardless of the sealing technique. Fungal populations at this sampling were generally less in treated plots than in the controls, but were higher under plastic seal. At this time, changes in invertase and amylase activities did not correspond to increased microbial numbers. Sixteen weeks after applications of KN3, bacterial populations in treated plots did not differ significantly from controls, but remained higher in plastic-sealed than water-sealed plots. Fungal populations under plastic seal had changed little and remained significantly lower in treated water-sealed plots than in controls. The earlier recorded reduction in invertase and amylase activities was still evident at the final sampling.

Evaluation of Combination Treatment Processes for the Microbial Decontamination of Pork Trim†

2001 ◽  
Vol 64 (3) ◽  
pp. 335-342 ◽  
Author(s):  
MAURICIO M. CASTELO ◽  
DONG-HYUN KANG ◽  
GREGORY R. SIRAGUSA ◽  
MOHAMMAD KOOHMARAIE ◽  
ELAINE D. BERRY
Keyword(s):  
Lactic Acid ◽  
Storage Period ◽  
Hot Water ◽  
Microbial Populations ◽  
Aerobic Bacteria ◽  
Psychrotrophic Bacteria ◽  
C Storage ◽  
Combination Treatments ◽  
Treatment Processes ◽  
Hot Air

Combination treatment processes for the microbial decontamination of pork trim were developed and evaluated. Lean pork trim tissue (LPT) and fat-covered pork trim tissue (FPT) inoculated with swine feces were treated with intervention processes as follows: (i) control (untreated), (ii) water (15°C, 120 s), (iii) water followed by lactic acid wash (15°C, 75 s), (iv) combination 1 (water plus hot water [65.5°C, 15 s] plus hot air [510°C, 60 s] plus lactic acid), (v) combination 2 (water plus hot water [82.2°C, 15 s] plus hot air [510°C, 75 s] plus lactic acid), and (vi) combination 3 (water plus hot water [82.2°C, 45 s] plus hot air [510°C, 90 s] plus lactic acid). Populations of aerobic bacteria, psychrotrophic bacteria, coliforms, Escherichia coli, and lactic acid bacteria were determined before and after treatment and at days 2 and 7 of 4°C storage. Regardless of the intervention treatment, lower microbial populations were observed on FPT than on LPT immediately after treatment and during the 7-day storage period. Both LPT and FPT treated with water plus lactic acid, combination 1, combination 2, and combination 3 had lower remaining populations of all microbial groups immediately after treatment than did water-treated samples. Populations of aerobic bacteria, coliforms, E. coli, and lactic acid bacteria on either LPT or FPT did not statistically increase during the 7-day storage period. On LPT, populations of psychrotrophicbacteria grew during 4°C storage but remained lower at day 7 on LPT treated by combinations 2 and 3 (2.29 and 1.89 log10 CFU/cm2, respectively) than on LPT treated with water (4.07 log10 CFU/cm2) or water plus lactic acid (3.52 log10 CFU/cm2). Populations of psychrotrophic bacteria remained below detectable levels throughout the 7-day storage on FPT treated with water plus lactic acid or any of the three combination treatments. Treatment of pork trim with any of the combination treatments significantly (P &lt; 0.05) affected the color and emulsion stability of the ground pork. Water and water plus lactic acid were the most favorable treatments in reducing microbial populations on pork trim without affecting the quality attributes of the ground pork.

scholarly journals Variation in Disease Severity Caused by Phytophthora cinnamomi, P. plurivora, and Pythium cryptoirregulare on Two Rhododendron Cultivars

Plant Disease ◽  
2018 ◽  
Vol 102 (12) ◽  
pp. 2560-2570 ◽  
Author(s):  
Jerry E. Weiland ◽  
Carolyn F. Scagel ◽  
Niklaus J. Grünwald ◽  
E. Anne Davis ◽  
Bryan R. Beck ◽  
...  
Keyword(s):  
Disease Control ◽  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Severe Disease ◽  
Phytophthora Species ◽  
Relative Resistance ◽  
Inoculum Level ◽  
Phytophthora Root Rot ◽  
Mild Disease ◽  
Comparative Information

Rhododendrons are an important crop in the ornamental nursery industry, but are prone to Phytophthora root rot. Phytophthora root rot is a continuing issue on rhododendrons despite decades of research. Several Phytophthora species are known to cause root rot, but most research has focused on P. cinnamomi, and comparative information on pathogenicity is limited for other commonly encountered oomycetes, including Phytophthora plurivora and Pythium cryptoirregulare. In this study, three isolates each of P. cinnamomi, P. plurivora, and Py. cryptoirregulare were used to inoculate rhododendron cultivars Cunningham’s White and Yaku Princess at two different inoculum levels. All three species caused disease, especially at the higher inoculum level. P. cinnamomi and P. plurivora were the most aggressive pathogens, causing severe root rot, whereas Py. cryptoirregulare was a weak pathogen that only caused mild disease. Within each pathogen species, isolate had no influence on disease. Both P. cinnamomi and P. plurivora caused more severe disease on Cunningham’s White than on Yaku Princess, suggesting that the relative resistance and susceptibility among rhododendron cultivars might be similar for both pathogens. Reisolation of P. cinnamomi and P. plurivora was also greater from plants exhibiting aboveground symptoms of wilting and plant death and belowground symptoms of root rot than from those without symptoms. Results show that both P. cinnamomi and P. plurivora, but not Py. cryptoirregulare, are important pathogens causing severe root rot in rhododendron. This study establishes the risks for disease resulting from low and high levels of inoculum for each pathogen. Further research is needed to evaluate longer term risks associated with low inoculum levels on rhododendron health and to explore whether differences among pathogen species affect disease control.

Seasonal variation in nitrogen fixation, associated microbial populations, and carbohydrates in roots and rhizomes of Typha latifolia (Typhaceae)

1984 ◽  
Vol 62 (9) ◽  
pp. 1965-1967 ◽  
Author(s):  
David D. Biesboer
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
Anaerobic Bacteria ◽  
Typha Latifolia ◽  
Root Surface ◽  
Microbial Populations ◽  
Aerobic Bacteria ◽  
Free Sugar ◽  
Fixation Rate ◽  
Reduction Assay

Seasonal changes in nitrogen fixation, numbers of nitrogen-fixing bacteria associated with the roots, and rhizome–root carbohydrates were studied for the broad-leaved cattail, Typha latifolia L. Populations of anaerobic and aerobic diazotrophic bacteria were present on the root surface. Anaerobic bacteria predominated in the diazotrophic association, were more active in the acetylene reduction assay, and generally outnumbered aerobic bacteria by 2 to 1 during maximum rates of seasonal nitrogen fixation. The observed maximum nitrogen fixation rate coincided closely with reproductive development in Typha and peak microbial populations. Starch levels in rhizomes were nearly depleted during the middle of the growing season, whereas free sugar concentrations remained stable. Sugar concentrations in the roots increased rapidly during rhizome–root growth and decreased rapidly prior to peak nitrogenase activity.

scholarly journals Phytophthora Root Rot of Blueberry Increases with Frequency of Flooding

HortScience ◽  
1999 ◽  
Vol 34 (4) ◽  
pp. 693-695 ◽  
Author(s):  
Amal de Silva ◽  
Keith Patterson ◽  
Craig Rothrock ◽  
Ron McNew
Keyword(s):  
Disease Severity ◽  
Root Rot ◽  
Phytophthora Cinnamomi ◽  
Disease Incidence ◽  
Severe Disease ◽  
Vaccinium Corymbosum ◽  
Root Infection ◽  
Phytophthora Root Rot ◽  
Severity Rating ◽  
Linear Relationships

Phytophthora root rot is a severe disease on blueberry (Vaccinium corymbosum L.) in poorly drained soils. Little is known about how mulching and frequent waterlogging affect disease severity in blueberries. Phytophthora cinnamomi Rands was grown on rice hulls, which were incorporated into the soil at the rate of 10% (v:v). Waterlogging conditions were imposed for 48 hours 1 week after planting on mulched and nonmulched blueberry plants at weekly, biweekly, and monthly intervals for a total of 3 months. Control plants were not subjected to flooding. The severity of Phytophthora root rot increased with time. Significant linear relationships were found between flooding interval and disease severity rating of shoot, percentage of root infection, and shoot and root dry weights of plants. Disease symptoms were minimal in control plants, but shoot disease rating and percentage of root infection were high in mulched and nonmulched plants that were flooded every week. Shoot and root dry weights were higher in 1997 than in 1996. In 1996, mulched plants had higher shoot dry weights than did nonmulched plants. Disease incidence was higher with weekly and biweekly flooding than with monthly or no flooding. However, mulching did not affect root infection.

Reduction of Bacteria on Pork Carcasses Associated with Chilling Method

2003 ◽  
Vol 66 (6) ◽  
pp. 1019-1024 ◽  
Author(s):  
V. P. CHANG ◽  
E. W. MILLS ◽  
C. N. CUTTER
Keyword(s):  
Salmonella Typhimurium ◽  
Meat Products ◽  
Microbial Populations ◽  
Aerobic Bacteria ◽  
Campylobacter Coli ◽  
Test Results ◽  
Bacterial Populations ◽  
Layer Method ◽  
Agar Layer ◽  
Low Levels

In addition to reducing the temperature of pork carcasses immediately after slaughter and before fabrication, blast chilling (snap chill) or conventional chilling can reduce bacterial populations associated with fresh meats. However, there is little information on bacteria survival resulting from the freeze or chill injury of meat products. In this study, porcine fecal slurries with and without pathogens (Listeria monocytogenes, Salmonella Typhimurium, and Campylobacter coli) were inoculated onto skin-on and skin-off pork surfaces and subjected to industry-specific blast or conventional chilling conditions. A thin agar layer method was used for the recovery of freeze- or chill-injured cells. Test results indicated that there were no statistically significant (P &gt; 0.05) differences between blast and conventional chilling treatments with respect to the reduction of high and low inoculation levels of mesophilic aerobic bacteria, total coliforms, or Escherichia coli on either skin-on or skin-off surfaces. Chilling treatments did not differ significantly (P &gt; 0.05) with respect to their ability to reduce low (3 log10 CFU/cm2) levels of L. monocytogenes and Salmonella Typhimurium. However, C. coli was reduced to undetectable levels, even after enrichment, on pork surfaces inoculated with low levels (3 log10 CFU/cm2) and subjected to blast chilling. Blast and conventional chilling treatments were more effective against all pathogenic bacterial populations when pork surfaces where inoculated at high levels (5 log10 CFU/cm2). The effects of chilling techniques on microbial populations could provide pork processors with an additional intervention for pork slaughter or information to modify and/or improve the chilling process. The information obtained from this study has the potential to serve as a means of producing a microbiologically safer product.

Variations in External and Internal Microbial Populations in Shell Eggs during Extended Storage

2004 ◽  
Vol 67 (12) ◽  
pp. 2657-2660 ◽  
Author(s):  
D. R. JONES ◽  
M. T. MUSGROVE ◽  
J. K. NORTHCUTT
Keyword(s):  
Storage Period ◽  
Microbial Populations ◽  
Aerobic Bacteria ◽  
Microbial Quality ◽  
Shell Eggs ◽  
External Shell ◽  
Processing Line ◽  
Yeasts And Molds

The current project was conducted to determine the microbial quality of commercially processed shell eggs during extended storage. Unwashed eggs were collected at the accumulator before entering the processing line. Washed eggs were retrieved after placement in flats. All eggs were stored on pulp flats at 4°C for 10 weeks. Twelve eggs from each treatment were rinsed on the day of collection and during each week of storage. After rinsing, eggs were sanitized in ethanol, and contents were aseptically collected. Total aerobes, yeasts and molds, Enterobacteriaceae, and pseudomonads were enumerated from shell rinses and pooled egg contents. During storage, no differences were found between unwashed and washed eggs for Enterobacteriaceae and pseudomonads in either shell rinses or contents. No differences were found between treatments for population levels of total aerobes or yeasts and molds in the egg contents throughout the storage period. Significant differences between treatments were found at each week of storage for external shell contamination by total aerobes. The highest unwashed egg contamination occurred at week 8 of storage and the lowest was at weeks 0 and 1 of storage. The highest shell contamination with aerobic bacteria on the washed eggs was found at week 0 of storage and the lowest was at week 7. Yeast and mold contamination determined by shell rinses was also significantly different between treatments at each week of storage. Commercially washed eggs were significantly less contaminated than were unwashed eggs for the populations monitored.

Impact of Commercial Processing on the Microbiology of Shell Eggs

2005 ◽  
Vol 68 (11) ◽  
pp. 2367-2375 ◽  
Author(s):  
MICHAEL T. MUSGROVE ◽  
DEANA R. JONES ◽  
JULIE K. NORTHCUTT ◽  
MARK A. HARRISON ◽  
NELSON A. COX
Keyword(s):  
Microbial Populations ◽  
Aerobic Bacteria ◽  
Shell Eggs ◽  
E Coli ◽  
Processing Line ◽  
Commercial Processing ◽  
Egg Shell ◽  
Yeasts And Molds ◽  
Pooled Samples ◽  
Processing Steps

Shell egg microbiology has been studied extensively, but little information is available on how modern U.S. processing conditions impact microbial populations. As regulations are being drafted for the industry, such information can be important for determining processing steps critical to product safety. Five different shell egg surface microbial populations (aerobic bacteria, yeasts and molds, Enterobacteriaceae, Escherichia coli, and Salmonella) were monitored at 12 points along the processing line (accumulator, prewash rinse, washer 1, washer 2, sanitizer, dryer, oiler, scales, two packer head lanes, rewash entrance, and rewash exit). Three commercial facilities were each visited three times, a total of 990 eggs were sampled, and 5,220 microbiological samples were subsequently analyzed. Although variations existed in concentrations of microorganisms recovered from each plant, the patterns of fluctuation for each population were similar at each plant. On average, aerobes, yeasts and molds, Enterobacteriaceae, and E. coli prevalence were reduced by 30, 20, 50, and 30%, respectively, by the end of processing. The microbial concentrations (log CFU per milliliter) in the egg rinse collected from packer head lanes were decreased by 3.3, 1.3, 1.3, and 0.5, respectively, when compared with those of rinses collected from eggs at the accumulator. Salmonella was recovered from 0 to 48% of pooled samples in the three repetitions. Higher concentrations of Salmonella were recovered from preprocessed than from in-process or ready-to-pack eggs. These data indicate that current commercial practices decrease microbial contamination of egg shell surfaces.

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