Influence of Pythium oligandrum Biocontrol on Fungal and Oomycete Population Dynamics in the Rhizosphere

Abstract

Fungal and oomycete populations and their dynamics were investigated following the introduction of the biocontrol agent Pythium oligandrum into the rhizosphere of tomato plants grown in soilless culture. Three strains of P. oligandrum were selected on the basis of their ability to form oospores (resting structures) and to produce tryptamine (an auxin-like compound) and oligandrin (a glycoprotein elicitor). Real-time PCR and plate counting demonstrated the persistence of large amounts of the antagonistic oomycete in the rhizosphere throughout the cropping season (April to September). Inter-simple-sequence-repeat analysis of the P. oligandrum strains collected from root samples at the end of the cropping season showed that among the three strains used for inoculation, the one producing the smallest amount of oospores was detected at 90%. Single-strand conformational polymorphism analysis revealed increases in the number of members and the complexity of the fungal community over time. There were no significant differences between the microbial ecosystems inoculated with P. oligandrum and those that were not treated, except for a reduction of Pythium dissotocum (ubiquitous tomato root minor pathogen) populations in inoculated systems during the last 3 months of culture. These findings raise interesting issues concerning the use of P. oligandrum strains producing elicitor and auxin molecules for plant protection and the development of biocontrol.

Transformation of the endochitinase gene Chi67-1 in Clonostachys rosea 67-1 increases its biocontrol activity against Sclerotinia sclerotiorum

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Soil pathogen communities associated with native and non‐native Phragmites australis populations in freshwater wetlands

“…), allowing some nonpathogenic species to induce positive PSFs by suppressing primary pathogenic species (Vallance et al. ), whereas other co‐occurring species may have no apparent impact on primary pathogens (Suffert and Guibert ). A more detailed understanding of the distribution and dynamics of pathogens, nonpathogens, and host‐associated mutualists and commensals will provide greater insights for understanding plant–microbe interactions, and the roles they play in plant community dynamics and plant invasions.…”

Use of QuantitativePCRDetection Methods to Study Biocontrol Agents and Phytopathogenic Fungi and Oomycetes in Environmental Samples

“…Authors presumed the existence of a balanced antagonism between the virulence of the colonizing endophyte and the plant defence response. Vallance et al (2009) studied the influence of a biocontrol agent (Pythium oligandrum) on fungal and oomycete population dynamics in the rhizosphere and, surprisingly, found that, with few exceptions, there were no significant differences between the microbial ecosystems inoculated with P. oligandrum and those that were not treated. In another study, qPCR proved to be more sensitive than dilutions on a selective media to detect and quantify a potential BCA (Plectosphaerella cucumerina) of potato cyst nematodes in soil (Atkins et al 2003).…”