2.2.126
INVESTIGATION OF THE GENETIC DIVERSITY OF ERYSIPHE SP. INFECTING RHODODENDRON SPP.
INVESTIGATION OF THE GENETIC DIVERSITY OF ERYSIPHE SP. INFECTING RHODODENDRON SPP.
DM KENYONl, J BRUNDIN2, GR DIXON3 and S. HELFER4
lNational Institute of Agricultural Botany, Huntingdon Road, Cambridge CB3 OLE, UK; 2 Department of Plant Breeding Research, Swedish University of Agricultural Sciences, 268 31 Sweden; 3Department of Bioscience & Biotechnology, University of Strathclyde, Glasgow GI IXQ, UK; 4Royal Botanic Garden, Edinburgh, Inverleith Row, Edinburgh EH3 5LR, UK
Background and objectives
Erysiphe sp. which causes powdery mildew on Rhododendron is the most serious foliar pathogen of this valuable horticultural crop [1]. In Europe this diseases was initial seen in Scotland from where it has subsequently spread throughout the UK and to other area's of Northern Europe [2]. Subsequently the disease has also been identified in North America and Oceania. In the UK over the last ten years the disease has increased in pathogenicity and developed resistance to certain fungicides. There is then a need for a detailed understanding of the structure of this pathogen population and how it relates to that found elsewhere in the world.
Materials and methods
Random amplified polymorphic DNA (RAPD) markers were used in this study to investigate the genetic diversity of the Erysiphe sp. causing Rhododendron powdery mildew. DNA from isolates collected throughout Britain were amplified by polymerase chain reaction (PCR), employing 20 random 10-mer primers, revealing a large number of polymorphisms. A second collection of Rhododendron powdery mildew isolates were collected from several sites in France, New Zealand and the United States of America. These isolates where studied using the same set of primers with their relative diversity calculated by principle component analysis.
Results and conclusions
The isolates from southern and northern England, respectively, formed two distinct groups with high internal relatedness, whereas the Scottish isolates formed a more diverse population, associating with both of the English clusters. This is explained by the presumed earlier establishment of the Scottish population, allowing greater time for diversification. Both English populations are thought to have originated from transfers of infected plant material from Scotland and would, therefore, be expected to show relatedness to this group. Isolates collected from Eire, France, New Zealand and the United States of America were analysed using the same set of markers and their diversity related to the UK populations.
References
I. Kenyon DM, Dixon GR, Helfer S, 1995. Plant Pathology 44, 350-54.
2. Kenyon DM, 1995 PhD Thesis, Strathclyde University.