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Intraspecific and within-isolate sequence variation in the ITS rRNA gene region of Pythium mercuriale sp. nov.

Lassaad Belbahri1, Adèle McLeod, Bernard Paul

  • 1Plants and Pathogens Group, Research Institute Earth Nature and Landscape, School of Engineering of Lullier, University of Applied Sciences of Western Switzerland, Jussy, Switzerland.

FEMS Microbiology Letters
|May 16, 2008
PubMed

Insights

Genetic analysis of Pythium isolates revealed significant internal sequence variations, challenging previous assumptions. These findings led to the identification of a new species, Pythium mercuriale, with unique genetic characteristics.

Area of Science:

  • Mycology
  • Molecular Biology
  • Plant Pathology

Background:

  • Previous studies suggested limited genetic variation within Pythium isolates.
  • Morphological and internal transcribed spacer (ITS) rRNA gene sequences were used to investigate Pythium isolates.

Purpose of the Study:

  • To investigate genetic variations within and between Pythium isolates.
  • To characterize a novel Pythium species based on genetic and morphological data.

Main Methods:

  • Sequencing of the internal transcribed spacer (ITS) region of rRNA genes.
  • Analysis of nuclear genes (elongation factor 1 alpha, beta-tubulin) and a mitochondrial gene (nadh1).
  • Phylogenetic analyses using maximum likelihood.

Main Results:

  • Significant sequence and length polymorphisms were found within and between isolates in ITS regions, contrary to expectations.
  • High levels of heterozygosity and multiple alleles were observed in nuclear genes.
  • A new species, Pythium mercuriale, was identified, characterized by specific morphological features.
  • Phylogenetic analyses placed P. mercuriale in a distinct clade between Pythium and Phytophthora.

Conclusions:

  • Pythium isolates exhibit substantial genetic diversity, including within single isolates.
  • Pythium mercuriale represents a novel species with a unique genetic and morphological profile.
  • The genetic findings necessitate a re-evaluation of Pythium species identification and classification.

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