Skip to main content

Molecular variability of sunflower downy mildew, Plasmopara halstedii, from different continents

Buy Article:

$50.00 plus tax (Refund Policy)

Abstract:

Downy mildew of sunflower (Helianthus annuus L.), caused by the pathogen Plasmopara halstedii, is a potentially devastating disease. Seventy-seven isolates of P. halstedii collected in twelve countries from four continents were investigated for RAPD polymorphism with 21 primers. The study led to a binary matrix, which was subjected to various complementary analyses. This is the first report on the international genetic diversity of the pathogen. Similarity indices ranged from 89% to 100%. Neither a consensus unweighted pair group method with arithmetic means (UPGMA) tree constructed after bootstrap resampling of markers nor a principal component analysis based on distance matrix revealed very consistent clusterings of the isolates, and groups did not fit race or geographical origins. Phylogenies were probably obscured by limited diversity. Analysis of molecular variance (AMOVA) and Nei's genetic diversity statistics gave similar conclusions. Most of the genetic diversity was attributable to individual differences. The most differentiated races also had the lowest within-diversity indices, which suggest that they appeared recently with strong bottleneck effects. Our analyses suggest that this pathogen is probably homothallic or has an asexual mode of reproduction and that gene flow among countries can occur through commercial exchanges. Knowledge of the downy mildew populations' structure at the international level will help to devise strategies for controlling this potentially devastating disease.Key words: RAPD, Helianthus annuus, genetic diversity, plant pathogen.

Le mildiou du tournesol (Helianthus annuus L.), causé par Plasmopara halstedii, est une maladie potentiellement dévastatrice. Le polymorphisme RAPD de 77 isolats de P. halstedii recueillis dans 12 pays de quatre continents a été étudié à l'aide de 21 amorces. L'étude a généré une matrice binaire qui a été soumise à diverses analyses complémentaires. Il s'agit ici de la première description de la diversité génétique internationale de ce pathogène. Les indices de similitude se situaient entre 89 % et 100 %. Ni un arbre consensus de groupe de paires non-pondérées en utilisant la moyenne mathématique (UPGMA) construit après ré-échantillonnage circulaire de marqueurs, ni une analyse en composantes principales basée sur une matrice des distances n'ont révélé de véritables regroupements des isolats, et les groupes ne correspondaient pas aux origines raciales ou géographiques. Les phylogénies ont probablement été obscurcies par une diversité limitée. L'AMOVA, statistiques de diversité génétique de Nei, a mené à des conclusions semblables. Les races les plus différenciées démontraient également les indices de diversité intrinsèque les plus bas, ce qui indique qu'elles sont apparues récemment avec d'importants effets d'étranglement. Nos analyses suggèrent que ce pathogène est probablement homothallique ou a un mode de reproduction asexuée, et que le flux génétique entre les pays peut se faire par le biais d'échanges commerciaux. Une connaissance de la structure des populations de mildiou au niveau international facilitera la mise au point de stratégies visant à contrôler cette maladie potentiellement dévastatrice.Mots clés : RAPD, Helianthus annuus, diversité génétique, pathogène végétal.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: 2003-08-01

More about this publication?
  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
  • Information for Authors
  • Submit a Paper
  • Subscribe to this Title
  • Terms & Conditions
  • Sample Issue
  • Reprints & Permissions
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free ContentFree content
  • Partial Free ContentPartial Free content
  • New ContentNew content
  • Open Access ContentOpen access content
  • Partial Open Access ContentPartial Open access content
  • Subscribed ContentSubscribed content
  • Partial Subscribed ContentPartial Subscribed content
  • Free Trial ContentFree trial content
Cookie Policy
X
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more