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GrainGenes Reference Report: AEM-67-4414

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Reference	AEM-67-4414
Title	Changes in populations of rhizosphere bacteria associated with take-all disease of wheat
Journal	Applied and Environmental Microbiology
Year	2001
Volume	67
Pages	4414-4425
Author	Gardener BBM Weller DM
Abstract	Take-all, caused by Gaeumannomyces graminis var. tritici, is one of the most important fungal diseases of wheat worldwide. Knowing that microbe-based suppression of the disease occurs in monoculture wheat fields following severe outbreaks of take-all, we analyzed the changes in rhizosphere bacterial communities following infection by the take-all pathogen. Several bacterial populations were more abundant on diseased plants than on healthy plants, as indicated by higher counts on a Pseudomonas-selective medium and a higher fluorescence signal in terminal restriction fragment length polymorphism analyses of amplified 16S ribosomal DNA (rDNA). Amplified rDNA restriction analysis (ARDRA) of the most abundant cultured populations showed a shift in dominance from Pseudomonas to Chryseobacterium species in the rhizosphere of diseased plants. Fluorescence-tagged ARDRA of uncultured rhizosphere washes revealed an increase in ribotypes corresponding to several bacterial genera, including those subsequently identified by partial 16S sequencing as belonging to species of alpha-, beta-, and gamma-proteobacteria, sphingobacteria, and flavobacteria. The functional significance of some of these populations was investigated in vitro. Of those isolated, only a small subset of the most abundant Pseudomonas spp. and a phlD(+) Pseudomonas sp. showed any significant ability to inhibit G. graminis var. tritici directly. When cultured strains were mixed with the inhibitory phlD(+) Pseudomonas strain, the Chryseobacterium isolates showed the least capacity to inhibit this antagonist of the pathogen, indicating that increases in Chryseobacterium populations may facilitate the suppression of take-all by 2,4-diacetylphloroglucinol-producing phlD(+) pseudomonads
External Databases	Pubmed: 11571137
Keyword	[ Hide all but 1 of 64 ] 2,4-diacetylphloroglucinol alpha ardra bacteria bacterial bacterial community bacterial populations bark compost media biocontrol capacity community count disease dna dominance field flavobacteria fluorescence fluorescent pseudomonads fragment length polymorphism fungal fungal diseases gaeumannomyces graminis graminis graminis var tritici healthy in vitro increase infection inhibit isolate length polymorphism media microbiology monoculture oct outbreaks pathogen polymorphism population pseudomonads pseudomonas rdna restriction restriction analysis restriction fragment length rflp rhizobacteria rhizoctonia damping-off rhizosphere ribosomal dna ribotype sequencing signal strain suppression take-all take-all disease terminal restriction fragment terminal restriction fragment length polymorphism tritici vitro washington worldwide

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