title: Bacterial diversity on the surface of potato tubers in soil and the influence of the plant genotype.
abstract: The surface of tubers might be a reservoir for bacteria that are disseminated with seed potatoes or that affect postharvest damage. The numbers of culturable bacteria and their antagonistic potential, as well as bacterial community fingerprints were analysed from tubers of seven field-grown potato genotypes, including two lines with tuber-accumulated zeaxanthin. The plant genotype significantly affected the number of culturable bacteria only at one field site. Zeaxanthin had no effect on the bacterial plate counts. In dual culture, 72 of 700 bacterial isolates inhibited at least one of the potato pathogens Rhizoctonia solani, Verticillium dahliae or Phytophthora infestans, 12 of them suppressing all three. Most of these antagonists were identified as Bacillus or Streptomyces. From tubers of two plant genotypes, including one zeaxanthin line, higher numbers of antagonists were isolated. Most antagonists showed glucanase, cellulase and protease activity, which could represent mechanisms for pathogen suppression. PCR-DGGE fingerprints of the 16S rRNA genes of bacterial communities from the tuber surfaces revealed that the potato genotype significantly affected the Pseudomonas community structure at one site. However, the genotypes showed nearly identical fingerprints for Bacteria, Actinobacteria, Alphaproteobacteria, Betaproteobacteria, Bacillus and Streptomycetaceae. In conclusion, tuber-associated bacteria were only weakly affected by the plant genotype.
authors.affiliation: Julius Kühn-Institut (JKI) - Federal Research Centre for Cultivated Plants, Institute for Epidemiology and Pathogen Diagnostics, Braunschweig, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Weinert
authors.forename: Remo
authors.initials: R
authors.lastname: Meincke
authors.forename: Christine
authors.initials: C
authors.lastname: Gottwald
authors.forename: Holger
authors.initials: H
authors.lastname: Heuer
authors.forename: Michael
authors.initials: M
authors.lastname: Schloter
authors.forename: Gabriele
authors.initials: G
authors.lastname: Berg
authors.forename: Kornelia
authors.initials: K
authors.lastname: Smalla
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000235:genetics; D044822:Biodiversity; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000032:analysis; D058645:Denaturing Gradient Gel Electrophoresis; D005838:Genotype; D010802:Phylogeny; D035281:Plant Tubers / Q000235:genetics / Q000378:metabolism / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D012988:Soil Microbiology; D011198:Solanum tuberosum / Q000235:genetics* / Q000382:microbiology; D024341:Xanthophylls / Q000378:metabolism; D065146:Zeaxanthins
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D024341:Xanthophylls; D065146:Zeaxanthins