Evidence for<i>Pythium</i>as a Pathogen of Direct-Drilled Wheat in the Pacific Northwest

Cook, Robert; Sitton, J. W.; Waldher, J. T.

doi:10.1094/pd-64-102

Cited by 66 publications

(26 citation statements)

References 3 publications

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“…has never been reported. The positive association of clay with CRRD should not be surprising since soils with high clay content are prone to long periods of water saturation, and Pythium root rot is prevalent in wet soils (Cook et al, 1980;Martin and Loper, 1999). Knudsen et al (2002) reported a similar effect of soil clay content on Pythium damping-off in sugar beet.…”

Section: Article In Pressmentioning

confidence: 92%

Variation of Pythium-induced cocoyam root rot severity in response to soil type

Adiobo

Oumar

Perneel

et al. 2007

Soil Biology and Biochemistry

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In Cameroon, andosols are suspected to be suppressive to cocoyam (Xanthosoma sagittifolium) root rot disease (CRRD) caused by the Oomycete pathogen Pythium myriotylum. To determine factors involved in disease suppressiveness, andosols were studied in comparison to ferralsols known to be disease-conducive. Soil samples were collected from six sites of which three were in andosols around Mount Cameroon (Boteva, Njonji, and Ekona) and the three others in ferralsols (Bakoa, Lapkwang, and Nko'o canane). Greenhouse plant experiments were used to assess soil suppressiveness. Soils were artificially infested with two levels of P. myriotylum inoculum (100 and 300 mycelia strands g À1 soil) prior to planting cocoyam. Disease severity was significantly higher in ferralsols than in andosols. Andosols partly lost their suppressiveness as a result of autoclaving and could recover suppressiveness following recolonisation by their original microflora. Soil microbial groups implicated in the disease suppression were investigated by assessing the effect of fungicide, bactericide, and pasteurisation on andosol suppressiveness. Andosols suppressiveness was significantly reduced following pasteurisation and treatment with fungicide and bactericide. The possible influence of microbial biomass on andosol suppressiveness was investigated by comparing microbial populations of suppressive andosols to those in andosols that had lost suppressiveness. A comparative analysis of suppressive and conducive soil properties was performed to identify soil variables, which may contribute to soil suppressiveness. Soil chemical analysis results showed that organic matter content was higher in andosols than in ferralsols. In addition, the content of mineral nutrients such as Ca, K, Mg and N, was higher in andosols than in ferralsols. These soil variables negatively correlated with disease severity. By contrast, sand and clay, which were higher in ferralsols than in andosols, were positively related to disease severity. This study has confirmed the suppressive nature of andosols from Mount Cameroon to CRRD. The results suggest that high organic matter content is likely mediating P. myriotylum suppression in andosols by improving soil structure, increasing soil nutrient content and microbial biomass, and sustaining microbial activity. r

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Section: Article In Pressmentioning

confidence: 92%

Variation of Pythium-induced cocoyam root rot severity in response to soil type

Adiobo

Oumar

Perneel

et al. 2007

Soil Biology and Biochemistry

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“…Folwell et al (1991) estimated that take-all disease caused 20% yield reduction on wheat, based on soil fumigation studies and grower surveys. Treatment with metalaxyl, a fungicide specific for oomycetes, resulted in wheat yield increases of 1-2 tons/acre, due to control of Pythium (Cook et al 1980). Treatment with soil fumigation increased wheat yields by 3-36% (Cook et al 1987).…”

Section: Economic Impacts Of Soilborne Pathogens and Root Diseasesmentioning

confidence: 99%

The rhizosphere: a playground and battlefield for soilborne pathogens and beneficial microorganisms

et al. 2008

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The rhizosphere is a hot spot of microbial interactions as exudates released by plant roots are a main food source for microorganisms and a driving force of their population density and activities. The rhizosphere harbors many organisms that have a neutral effect on the plant, but also attracts organisms that exert deleterious or beneficial effects on the plant. Microorganisms that adversely affect plant growth and health are the pathogenic fungi, oomycetes, bacteria and nematodes. Most of the soilborne pathogens are adapted to grow and survive in the bulk soil, but the rhizosphere is the playground and infection court where the pathogen establishes a parasitic relationship with the plant. The rhizosphere is also a battlefield where the complex rhizosphere community, both microflora and microfauna, interact with pathogens and influence the outcome of pathogen infection. A wide range of microorganisms are beneficial to the plant and include nitrogen-fixing bacteria, endo-and ectomycorrhizal fungi, and plant growth-promoting bacteria and fungi. This review focuses on the population dynamics and activity of soilborne pathogens and beneficial microorganisms. Specific attention is given to mechanisms involved in the tripartite interactions between beneficial microorganisms, pathogens and the plant. We also discuss how agricultural practices affect pathogen and antagonist populations and how these practices can be adopted to promote plant growth and health.

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“…(Cook, Sitton & Waldher 1980), both of which groups are pathogens, and some Pseudomonas spp. (Elliot & Lynch 1984;Simpfendorfer, Kirkegaard & Heenan 2001) which, while not pathogenic, nevertheless inhibit plant growth by releasing toxins.…”

Section: Interactions Between Soil Structure and Microbial Activity Tmentioning

confidence: 99%

‘Soil conditions and plant growth’

Passioura

2002

Plant Cell & Environment

332

179

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Plants can respond to soil conditions in ways that can not readily be explained in terms of the ability of the roots to take up water and nutrients. Roots may sense difficult conditions in the soil and thence send inhibitory signals to the shoots which harden the plants against the consequences of a deteriorating or restrictive environment, especially if the plants' water supply is at risk. Generally, this behaviour can be interpreted as feedforward responses to the soil becoming too dry or too hard, or to the available soil volume being very small as with bonsai plants, or to roots' becoming infected with pathogens. However, soil that is too soft or in which the roots are forced to grow in very large pores can also induce large conservative responses, the significance of which is unclear. The inhibitory signals may affect stomatal conductance, cell expansion, cell division and the rate of leaf appearance. Their nature is still under debate, and the debate is becoming increasingly complex, which probably signifies that a network of hormonal and other responses is involved in attuning the growth and development of a plant to its environment.

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Evidence forPythiumas a Pathogen of Direct-Drilled Wheat in the Pacific Northwest

Cited by 66 publications

References 3 publications

Variation of Pythium-induced cocoyam root rot severity in response to soil type

Variation of Pythium-induced cocoyam root rot severity in response to soil type

The rhizosphere: a playground and battlefield for soilborne pathogens and beneficial microorganisms

‘Soil conditions and plant growth’

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