European Journal of Plant Pathology

, Volume 126, Issue 2, pp 175–185

Pectobacterium carotovorum subsp. brasiliensis causing blackleg on potatoes in South Africa

  • Johanna J. van der Merwe
  • Teresa A. Coutinho
  • Lise Korsten
  • Jacqueline E. van der Waals
Original Research

DOI: 10.1007/s10658-009-9531-2

Cite this article as:
van der Merwe, J.J., Coutinho, T.A., Korsten, L. et al. Eur J Plant Pathol (2010) 126: 175. doi:10.1007/s10658-009-9531-2

Abstract

In South Africa during the 2006/2007 potato growing season, outbreaks of blackleg occurred, causing severe economic losses in commercial potato production fields. Symptoms were initially observed on only one stem per plant, on which the top leaves rolled upwards, wilted and became necrotic. As symptoms progressed to the lower leaves with subsequent leaf desiccation, a light to dark brown discolouration of the vascular system at the stem base developed, followed by external darkening. Under prevailing wet and humid conditions stems became slimy and pale. In the stems, the pith became necrotic and hollow. These symptoms were similar to those described in Brazil, where the causal agent was identified as a new subspecies, Pectobacterium carotovorum subsp. brasiliensis (Pbcb). Isolations from plants showing typical blackleg symptoms were made on CVP medium. Sequences and phylogenetic analysis of the partial 16S–23S rDNA intergenic spacer region indicated that the isolates were Pbcb. Comparison of PCR-RFLP patterns of the 16S–23S rDNA of isolates to reference cultures confirmed the identity of the South African blackleg strains as Pbcb, identical to strain 8 isolated in Brazil. This is the first report of Pbcb in South Africa and it appears to be the most important causal agent of blackleg in South Africa. The disease poses a major potential threat to the South African potato industry especially in terms of seed exports, tuber quality and yield.

Keywords

Blackleg-like symptomsSoft rotEconomic yield losses

Copyright information

© KNPV 2009

Authors and Affiliations

  • Johanna J. van der Merwe
    • 1
    • 2
  • Teresa A. Coutinho
    • 3
  • Lise Korsten
    • 1
  • Jacqueline E. van der Waals
    • 1
  1. 1.Department of Microbiology and Plant PathologyUniversity of PretoriaPretoriaSouth Africa
  2. 2.Syngenta South Africa (Pty) Ltd.Halfway HouseSouth Africa
  3. 3.Department of Microbiology and Plant Pathology, Forestry and Agricultural Institute (FABI)University of PretoriaPretoriaSouth Africa