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Applied and Environmental Microbiology, January 2006, p. 185-191, Vol. 72, No. 1
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.1.185-191.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Genetic Variability and Distribution of Mating Type Alleles in Field Populations of Leptosphaeria maculans from France

Lilian Gout,1,2 Maria Eckert,3 Thierry Rouxel,1 and Marie-Hélène Balesdent1*

Phytopathologie et Méthodologies de la Détection, INRA, F-78026 Versailles, France,1 Protection des Plantes, INA-PG, F-78850 Thiverval-Grignon, France,2 Rothamsted Research, Harpenden AL5 2JQ, United Kingdom3

Received 7 April 2005/ Accepted 3 October 2005

Leptosphaeria maculans is the most ubiquitous fungal pathogen of Brassica crops and causes the devastating stem canker disease of oilseed rape worldwide. We used minisatellite markers to determine the genetic structure of L. maculans in four field populations from France. Isolates were collected at three different spatial scales (leaf, 2-m2 field plot, and field) enabling the evaluation of spatial distribution of the mating type alleles and of genetic variability within and among field populations. Within each field population, no gametic disequilibrium between the minisatellite loci was detected and the mating type alleles were present at equal frequencies. Both sexual and asexual reproduction occur in the field, but the genetic structure of these populations is consistent with annual cycles of randomly mating sexual reproduction. All L. maculans field populations had a high level of gene diversity (H = 0.68 to 0.75) and genotypic diversity. Within each field population, the number of genotypes often was very close to the number of isolates. Analysis of molecular variance indicated that >99.5% of the total genetic variability was distributed at a small spatial scale, i.e., within 2-m2 field plots. Population differentiation among the four field populations was low (GST < 0.02), suggesting a high degree of gene exchange between these populations. The high gene flow evidenced here in French populations of L. maculans suggests a rapid countrywide diffusion of novel virulence alleles whenever novel resistance sources are used.

* Corresponding author. Mailing address: INRA, Unité PMDV, Route de Saint Cyr, 78026 Versailles Cedex, France. Phone: 33 1 30833229. Fax: 33 1 30833195. E-mail: mhb{at}versailles.inra.fr

Applied and Environmental Microbiology, January 2006, p. 185-191, Vol. 72, No. 1
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.1.185-191.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Plantegenest, M., Le May, C., Fabre, F. (2007). Landscape epidemiology of plant diseases. J R Soc Interface 4: 963-972 [Abstract] [Full Text]  


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