Ten polymorphic microsatellite loci identified from a small insert genomic library for Peronospora tabacina

Abstract

Ten polymorphic microsatellite loci for the obligate biotrophic, oomycete pathogen of tobacco, Peronospora tabacina, were identified from a small insert genomic library enriched for GT motifs. Eighty-five percent of the 162 loci identified were composed of dinucleotide repeats, whereas only 4% and 11% were tri-and tetra-nucleotide repeats respectively. About 82% of all the microsatellites were perfect and within the library; only about 7% of the loci were duplicated. Primers were designed for 63 loci; 10 loci were polymorphic, 19 were monomorphic and 34 either failed to amplify or produced ambiguous/inconsistent results. The 10 polymorphic loci were characterized with 44 isolates of P. tabacina collected from tobacco plants growing in Europe, the Near East and North and South America. The number of alleles per locus was either three or four with a mean of 3.2, and the mean number of genotypes per locus was 3.6. Observed heterozygosity was 0.32–0.95, whereas expected heterozygosity was 0.44–0.69 for these loci. All loci except PT054 did not conform to the Hardy-Weinberg distribution. Polymorphic information content (PIC) for the loci was 0.35–0.69 with a mean of 0.50. These microsatellite loci provide a set of markers sufficient to perform genetic diversity and population studies of P. tabacina, and possibly other species of Peronospora.

• blue mold
• downy mildew
• genetic diversity
• Oomycete
• Peronosporales
• plant disease
• simple sequence repeats
• SSRs
• tobacco

Acknowledgments

This study was supported by the US Department of Agriculture grant No. 58-6404-7-213.

Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the University of Tennessee or the United States Department of Agriculture. MT and ST are supported by the research program LOEWE (Landes-Offensive zur Entwicklung Wissenschaftlich-ökono-mischer Exzellenz) of Hessen’s Ministry of Higher Education, Research, and the Arts. FR is supported by a fellowship from the Ministry of Science and Education of Baden-Württemberg. We gratefully acknowledge support to O.S. from the European Association for Tobacco Research and Experimentation (AERET) in sampling P. tabacina field isolates from Europe and Near East.