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Phylogenetic analysis and Real Time PCR detection of a presumbably undescribed Peronospora species on sweet basil and sage

Published online by Cambridge University Press:  30 September 2005

Lassaad BELBAHRI ,
Gautier CALMIN ,
Jan PAWLOWSKI  and
Francois LEFORT
Lassaad BELBAHRI
Affiliation:
Laboratory of Applied Genetics, School of Engineering of Lullier, University of Applied Sciences of Western Switzerland, 150 Route de Presinge, 1254 Jussy, Switzerland. E-mail: lassaad.belbahri@etat.ge.ch
Gautier CALMIN
Affiliation:
Laboratory of Applied Genetics, School of Engineering of Lullier, University of Applied Sciences of Western Switzerland, 150 Route de Presinge, 1254 Jussy, Switzerland. E-mail: lassaad.belbahri@etat.ge.ch
Jan PAWLOWSKI
Affiliation:
Department of Zoology and Animal Biology, University of Geneva, Sciences III; 30, quai Ernest-Ansermet, 1211 Geneva, 4, Switzerland.
Francois LEFORT
Affiliation:
Laboratory of Applied Genetics, School of Engineering of Lullier, University of Applied Sciences of Western Switzerland, 150 Route de Presinge, 1254 Jussy, Switzerland. E-mail: lassaad.belbahri@etat.ge.ch
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Abstract

Downy mildew of sweet basil (Ocimum basilicum) has become a serious disease issue for the producers of sweet basil in Switzerland since it was first recorded in 2001. Reported in Africa in Uganda as early as 1933, major outbreaks of this disease in Europe were first noted in Italy in 1999 and in the USA from 1993. Previous reports have named the pathogen as Peronospora lamii. Its preferential hosts belong to the Lamiaceae family including basils (Ocimum spp.), mints (Menta spp.), sages (Salvia spp.) and other aromatics. This study investigated the taxonomic status of the downy mildew pathogen, using both morphological characters and molecular analysis of the ITS region of the rDNA. The inherent variability of conidial dimensions made species differentiation difficult. Sequence homology and phylogenetic analysis of nine collections of the Peronospora on sweet basil showed unique ITS sequences distinct from those of P. lamii and any other sequenced Peronospora species. This paper describes and illustrates the morphology of this presumably undescribed species of Peronospora. Its taxonomic position and relationships with other related species in the same genus are presented and discussed. In addition to this work, PCR primers for real time PCR analysis have been developed for the specific detection of this downy mildew pathogen from infected tissues or seeds. It is shown that these primers can also be used in classic PCR.

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Type
Research Article
Information
Mycological Research , Volume 109 , Issue 11 , November 2005 , pp. 1276 - 1287
Copyright
The British Mycological Society 2005

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