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.

Phytophthora cinnamomi: Population Densities in Forest Soils

1977 ◽  
Vol 25 (5) ◽  
pp. 461 ◽  
Author(s):  
G Weste ◽  
P Ruppin
Keyword(s):  
Environmental Factors ◽  
Soil Water ◽  
Phytophthora Cinnamomi ◽  
Soil Water Potential ◽  
Forest Community ◽  
Population Densities ◽  
Sclerophyll Forest ◽  
Soil Temperatures ◽  
Disease Extension ◽  
Pathogen Populations

Population densities of Phytophthora cinnamomi, associated disease and environmental factors were studied concurrently during a 2-year period in three different forest ecosystems. Pathogen populations showed seasonal variation, low values being obtained for winter months associated with soil temperatures less than 10°C. Populations increased with warmer temperatures for spring and summer, but declined during dry periods in late summer or early autumn when the soil water potential was lower than -9 bars, although at that period soil temperatures were favourable. High populations were recorded in autumn, then declined with decrease in soil temperatures during winter. Correlation coefficients indicated a highly significant relationship between pathogen populations and soil temperatures from autumn to early summer, and between soil moisture and pathogen population for summer and autumn, in the Brisbane Ranges independently of site. The same pattern was evident in wetter forests at Narbethong and savannah woodlands at Wilson's Promontory, although results were not significant. Disease was evident wherever the pathogen occurred among susceptible hosts. The savannah woodland, the dry shrubby sclerophyll forest and the wetter sclerophyll forest all contained susceptible dominants; consequently disease was associated with changes in the forest community such as early death of the understorey, later die-back and death of the trees, and an increase in sedges and in bare ground. Symptoms and deaths increased with time from invasion. The severity of disease and its rate of extension, apart from spread by free water, were associated with environmental factors such as shallow soil, poor drainage and low soil water-holding capacity. These were characteristic of the Brisbane Ranges, where destruction of the forest community was severe and the rate of disease extension rapid. In the deep krasnozem at Narbethong and the deep sands of Wilson's Promontory, destruction was confined to the most susceptible hosts, disease extension was continuous but slow, and deaths occurred in a mosaic throughout the infected zone.

Production of Sporangia by Phytophthora cinnamomi in Forest Soils

1979 ◽  
Vol 27 (6) ◽  
pp. 693 ◽  
Author(s):  
G Weste ◽  
K Vithanage
Keyword(s):  
Seasonal Variation ◽  
Forest Soils ◽  
Phytophthora Cinnamomi ◽  
Sandy Soils ◽  
Garden Soil ◽  
First Year ◽  
Soil Sterilization ◽  
Pilot Survey ◽  
Significant Seasonal Variation ◽  
Soil Temperatures

Sporangial production by Phytophthora cinnamomi was investigated during a 3-year period for three types of conducive forest soils. A pilot survey conducted during the first year included garden soil and demonstrated that all forest soils tested stimulated sporangial production, that the stimulus was reduced by soil sterilization, and that soils without P. cinnamomi provided a greater stimulus than soils from diseased sites. For the final 2 years of the investigation soil and root samples were collected from diseased plants at 3- monthly intervals, and soil filtrates were tested for their ability to stimulate sporangial production. Soil matric water potentials and soil temperatures were recorded concurrently. Three factors which influenced the soil and indirectly affected sporangial formation were soil temperature, soil matric water potential and the presence of a stimulus produced by certain living microorganisms. Sporangial production showed highly significant seasonal variation with maxima in spring. No sporangia were produced in summer. Differences in the numbers of sporangia produced in response to the different soil filtrates were also highly significant, the highest numbers being formed in response to sandy soils of Wilson's Promontory. These results, particularly the large release of zoospores during spring, are of great importance in the spread of disease, and should be considered in relation to roadmaking and forestry in diseased areas.

Seasonal Variation in Numbers of Chlamydospores in Victorian Forest Soils Infected With Phytophthora cinnamomi

1978 ◽  
Vol 26 (5) ◽  
pp. 657 ◽  
Author(s):  
G Weste ◽  
K Vithanage
Keyword(s):  
Seasonal Variation ◽  
Soil Water ◽  
Forest Soils ◽  
Phytophthora Cinnamomi ◽  
Soil Water Potential ◽  
Native Forest ◽  
Forest Sites ◽  
Significant Seasonal Variation ◽  
Different Types ◽  
Soil Temperatures

Chlamydospore numbers were counted for 2 years on replicated soil samples from three different types of naturally infected Victorian native forest. Soil temperatures and soil water potentials were recorded concurrently. A highly significant seasonal variation in chlamydospore numbers was observed with maxima from summer to autumn and minima from winter to spring. There was little variation either between replicates or between different forest soils in winter and spring counts, but there was highly significant variation between different forest sites during the large summer and autumn counts. At this period sandy soil contained five to 12 times the number of chlamydo- spores found in other soils. For example, in autumn 1977,286 chlamydospores were recorded per 50 g sample from deep sandy soils compared with 31 for krasnozem and 17 for shallow duplex soils. At this period soil temperatures were similar but the soil water potential for the duplex soil was very low (-82 bars).

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.

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

Forests ◽  
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.

scholarly journals Pathogenicity of four Phytophthora species on kauri in vitro and glasshouse trials

2014 ◽  
Vol 67 ◽  
pp. 54-59 ◽  
Author(s):  
I.J. Horner ◽  
E.G. Hough
Keyword(s):  
Plant Growth ◽  
Forest Soils ◽  
Phytophthora Cinnamomi ◽  
Phytophthora Species ◽  
The Other ◽  
Root Damage ◽  
Soil Inoculation

In kauri forest soils surveys Phytophthora taxon Agathis (PTA) P cinnamomi P multivora and P cryptogea were detected frequently In vitro and glasshouse studies determined that all four Phytophthora species produced lesions on excised kauri leaves and stems Lesion advance was significantly slower with P cinnamomi P multivora and P cryptogea than with PTA When 2yearold kauri seedlings were trunkinoculated lesion spread was rapid with PTA trunks were girdled and all trees died within 46 weeks Phytophthora cinnamomi P multivora and P cryptogea produced substantially smaller lesions than PTA no trees died and plant growth was only slightly suppressed Following soil inoculation with PTA all kauri seedlings died within 10 weeks There were no deaths following soil inoculation with P cinnamomi P multivora or P cryptogea although feeder root damage was observed and the respective pathogens were reisolated Results suggest that PTA is an aggressive pathogen and the other three species are weaker pathogens of kauri

scholarly journals Long-term effects of timber harvesting on hemicellulolytic microbial populations in coniferous forest soils

2015 ◽  
Vol 10 (2) ◽  
pp. 363-375 ◽  
Author(s):  
Hilary T C Leung ◽  
Kendra R Maas ◽  
Roland C Wilhelm ◽  
William W Mohn
Keyword(s):  
Forest Soils ◽  
Coniferous Forest ◽  
Timber Harvesting ◽  
Microbial Populations ◽  
Long Term Effects

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.

scholarly journals 285 CONTROL OF SOILBORNE ONION DISEASES WITH SOIL SOLARIZATION, FUMIGATION AND RESISTANT VARIETIES

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 471a-471
Author(s):  
Michael K. Thornton ◽  
S. Krishna Mohan
Keyword(s):  
Disease Incidence ◽  
Soil Solarization ◽  
Disease Development ◽  
Disease Resistant ◽  
Resistant Varieties ◽  
Soil Temperatures ◽  
Clear Plastic ◽  
Pathogen Populations ◽  
Metham Sodium

Pathogen populations, disease development and onion yield were compared in solarized, fumigated and non-treated plots during 1992 and 1993. Soil solarization was accomplished by covering plots with clear plastic for six weeks beginning in mid-August, prior to the year of onion production. Solarization was also combined with metham sodium, a plied prior to covering with plastic. Soil temperatures reached a maximum of 48°C at the 10 cm depth in solarized plots, and were consistently 10 to 15°C higher than in non-solarized plots. Disease resistant (Bravo) and susceptible (Valdez) onion cultivars were planted the following spring. Only the solarization + metham sodium treatment significantly controlled pink root and plate rot in 1992. In 1993, all solarization and fumigation treatments controlled pink root. Solarization and fumigation did not significantly increase yield in comparison to the check, except for the solarization + metham sodium treatment in 1992. Bravo exhibited lower disease incidence than Valdez in both years of the study. Bravo produced 32.7 t/ha and 6.2 t/ha higher yield than Valdez in 1992 and 1993, respectively.

Sign in / Sign up

Export Citation Format

Share Document