Genetic diversity of Fusarium oxysporum populations isolated from different soils in France

The genetic diversity of soil-borne: populations of Fusarium oxysporum was assessed using 350 isolates collected from six different French soils. All isolates were characterised by restriction fragment analysis of the PCR-amp lified ribosomal intergenic spacer (IGS). Twenty-six IGS types were identif ied among the 350 isolates analysed. Five to nine different IGS types were detected in each soil. None of the IGS types was common to all of the soils . An analysis of the molecular variance based on IGS type relationships and frequency revealed that the genetic structure of the populations of F. oxy sporum varied widely among the soils. Some populations were both highly div erse within the soils and differentiated between the soils. A possible rela tionship between the intrapopulation or interpopulation level of diversity and some external factors such as the soil type or the crop history was eva luated. A subsample representative of the diversity of the six populations was further characterised by analysing the genomic distribution of two tran sposable elements, impala and Fotl.. One to 10 copies of the imlpala elemen t were present in most of the isolates, irrespective of their soil of origi n. The Fotl element was only detected in 40% of the isolates originating fr om the three populations less diverse in terms of IGS types, but in 82.6% o f the isolates originating from the three more diverse populations. (C) 200 1 Federation of European Microbiological Societies. Published by Elsevier S cience B.V. All rights reserved.