title: Isolation and characterization of two strains of Fusarium oxysporum causing potato dry rot in Solanum tuberosum in Colombia.
abstract: BACKGROUND
  Fusarium oxysporum has worldwide distribution and causes severe vascular wilt or root rot in many plants. Strains are classified into formae speciales based on their high degree of host specificity, of which multilocus sequence typing provides a fairly good estimate.
  
  
  OBJECTIVE
  The main aim of this study was to identify the causal agent of an infected potato tuber in Colombia.
  
  
  METHODS
  Two F. oxysporum isolates were recovered from a potato tuber showing symptoms of dry rot. Both macroscopic and microscopic morphology differences were observed between the two isolates. Koch's postulates were verified and in quantitative tuber pathogenecity trials, both isolates induced moderate dry rot. Ribosomal internal transcribed spacer (ITS) and partial intergenic spacer region (IGS) sequences were PCR-amplified, sequenced and shown to be identical for the two isolates. A maximum parsimony phylogeny was created using F. oxysporum IGS sequences available in the Genebank database, which does not include sequences from the formae speciales tuberosi.
  
  
  RESULTS
  Our two isolates were most closely related to a red clover (Trifolium pratense) pathogenic isolate and two non-pathogenic F. oxysporum isolates from birdsfoot trefoil (Lotus corniculatus) and Lycopersicon sp. rhyzosphere (99% identity).
  
  
  CONCLUSIONS
  These experiments showed that our isolates are not restricted to potato and that a molecular marker is needed to differentiate the formae speciales since the IGS and EF-1α do not have the power to do it.
authors.affiliation: Laboratorio de Micología y Fitopatología LAMFU, Universidad de los Andes, Bogotá, Colombia.
authors.forename: Leonor
authors.initials: L
authors.lastname: García Bayona
authors.forename: Alejandro
authors.initials: A
authors.lastname: Grajales
authors.forename: Martha Emiliana
authors.initials: ME
authors.lastname: Cárdenas
authors.forename: Roberto
authors.initials: R
authors.lastname: Sierra
authors.forename: Gabriel
authors.initials: G
authors.lastname: Lozano
authors.forename: Manuel Fernando
authors.initials: MF
authors.lastname: Garavito
authors.forename: María Caridad
authors.initials: MC
authors.lastname: Cepero de García
authors.forename: Adriana
authors.initials: A
authors.lastname: Bernal
authors.forename: Pedro
authors.initials: P
authors.lastname: Jiménez
authors.forename: Silvia
authors.initials: S
authors.lastname: Restrepo
mesh_terms: D003105:Colombia; D005670:Fusarium / Q000302:isolation & purification*; D010935:Plant Diseases / Q000382:microbiology*; D011198:Solanum tuberosum / Q000382:microbiology*