title: Effect of long-term vineyard monoculture on rhizosphere populations of pseudomonads carrying the antimicrobial biosynthetic genes phlD and/or hcnAB.
abstract: The impact of repeated culture of perennial plants (i.e. in long-term monoculture) on the ecology of plant-beneficial bacteria is unknown. Here, the influence of extremely long-term monocultures of grapevine (up to 1603 years) on rhizosphere populations of fluorescent pseudomonads carrying the biosynthetic genes phlD for 2,4-diacetylphloroglucinol and/or hcnAB for hydrogen cyanide was determined. Soils from long-term and adjacent short-term monoculture vineyards (or brushland) in four regions of Switzerland were baited with grapevine or tobacco plantlets, and rhizosphere pseudomonads were studied by most probable number (MPN)-PCR. Higher numbers and percentages of phlD(+) and of hcnAB(+) rhizosphere pseudomonads were detected on using soil from long-term vineyards. On focusing on phlD, restriction fragment length polymorphism profiling of the last phlD-positive MPN wells revealed seven phlD alleles (three exclusively on tobacco, thereof two new ones). Higher numbers of phlD alleles coincided with a lower prevalence of the allele displayed by the well-studied biocontrol strain Pseudomonas fluorescens F113. The prevalence of this allele was 35% for tobacco in long-term monoculture soils vs. >60% in the other three cases. We conclude that soils from long-term grapevine monocultures represent an untapped resource for isolating novel biocontrol Pseudomonas strains when tobacco is used as bait.
authors.affiliation: Plant Pathology, Institute of Integrative Biology, Zürich, Switzerland.
authors.forename: Miroslav
authors.initials: M
authors.lastname: Svercel
authors.forename: Danilo
authors.initials: D
authors.lastname: Christen
authors.forename: Yvan
authors.initials: Y
authors.lastname: Moënne-Loccoz
authors.forename: Brion
authors.initials: B
authors.lastname: Duffy
authors.forename: Geneviève
authors.initials: G
authors.lastname: Défago
mesh_terms: D000383:Agriculture / Q000379:methods*; D000898:Antibiosis; D001426:Bacterial Proteins / Q000235:genetics; D044822:Biodiversity; D050891:Oxidoreductases Acting on CH-NH2 Group Donors / Q000235:genetics; D012150:Polymorphism, Restriction Fragment Length; D011549:Pseudomonas / Q000235:genetics / Q000302:isolation & purification*; D012988:Soil Microbiology; D013557:Switzerland; D014026:Nicotiana / Q000382:microbiology; D027843:Vitis / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; C096183:PhlD protein, Pseudomonas; D050891:Oxidoreductases Acting on CH-NH2 Group Donors; C112800:glycine dehydrogenase (cyanide-forming)