Ratios of cells with and without virulence genes in Rhodococcus fascians populations correlate with degrees of symptom development

Ekaterina V. Nikolaeva, Sook Young Park, Seogchan Kang, Tracey N. Olson, Seong H. Kim

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

Nikolaeva, E. V., Park, S.-Y., Kang, S., Olson, T. N., and Kim, S. H. 2009. Ratios of cells with and without virulence genes in Rhodococcus fascians populations correlate with degrees of symptom development. Plant Dis. 93:499-506. Rhodococcus fascians, a gram-positive phytopathogenic bacterium, causes fasciation and leafy galls on a wide range of monocotyledonous and dicotyledonous plants for which it requires the plasmid-borne fas operon. Strains isolated from symptomatic plants over a 20-year-period exhibited a high degree of variability when their virulence was assessed on garden pea seedlings. Polymerase chain reaction amplification of the fas-1 and fasR virulence genes from randomly chosen single colonies showed that many strains consisted of two subpopulations, of which one had lost these genes. Inoculation of pea seedlings with mixtures of fas-1-positive and -negative cells that originated from the same strain demonstrated a strong correlation (Pearson's r ≥ 0.9205) between the proportion of cells in the inoculum carrying the fas-1 gene and the severity of disease symptoms. The minimal concentration of fas-1-positive cells required for the development of small lateral shoots on pea seedlings was 2.5 × 10 4 CFU/ml (P ≤ 0.008), while the overall suppression of main stem growth was observed at 2.5 × 10 5 CFU/ml (P ≤ 0.019). These observations underline that care should be taken when the virulence of clinical R. fascians strains is evaluated.

Original languageEnglish (US)
Pages (from-to)499-506
Number of pages8
JournalPlant disease
Volume93
Issue number5
DOIs
StatePublished - May 1 2009

All Science Journal Classification (ASJC) codes

  • Agronomy and Crop Science
  • Plant Science

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