VIEW ARTICLE

Techniques

Use of Specific Repetitive Sequences in Peronospora tabacina for the Early Detection of the Tobacco Blue Mold Pathogen. Martin D. Wiglesworth, Ciba Plant Protection, 509 Scarlett Lane, Lansing, MI 48917; William C. Nesmith(2), Christopher L. Schardl(3), Daoxin Li(4), and Malcolm R. Siegel(5). (2)(3)(5)Department of Plant Pathology, University of Kentucky, Lexington 40546-0091; (4)Ohio State Biotechnology Center, 206 Rightmire Hall, 1060 Carmack Road, Columbus 43210. Phytopathology 84:425-430. Accepted for publication 13 January 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/Phyto-84-425.

A 232-bp DNA sequence was obtained from random amplified polymorphic DNA of Peronospora tabacina, the blue mold pathogen of tobacco. This sequence had homology to P. tabacina DNA but not to DNA of other downy mildew or oomycetous fungi tested. The fragment was determined to be part of a repetitive DNA sequence that was ubiquitous in a worldwide collection of P. tabacina. Oligonucleotides were designed for amplification of this sequence by polymerase chain reaction. The fragment was reliably amplified with amounts of DNA (1–10 fg) that are less than that contained in a single P. tabacina sporangiospore. Use of this technique enabled the detection of P. tabacina DNA directly in local lesions, systemic vascular infections, and other infected parts of tobacco plants. The use of spore traps followed by amplification of this fragment facilitated the prediction of a local disease epidemic. Use of this highly specific and reliable detection method could prove valuable for regulatory agencies and for epidemiological and etiological studies.