Mitochondrial DNA diversity and lineage determination of European isolates of Fusarium graminearum (Gibberella zeae) M. La´day 1 ,A ´ . Juha´sz 2 , G. Mule` 3 , A. Moretti 3 ,A ´ . Sze´csi 1 and A. Logrieco 3 1 Plant Protection Institute of the Hungarian Academy of Science, P.O. Box 102, 1525 Budapest, Hungary (Fax: +3614877-555; E-mail: mlad@nki.hu); 2 Department of Microbiology, Faculty of Sciences, University of Szeged, P.O. Box 533, H-6701 Szeged, Hungary; 3 Institute of Sciences of Food Production, CNR, Viale Einaudi 51, 70125 Bari, Italy Key words: identification, lineage distribution, mtDNA RFLP, scab Abstract Restriction fragment length polymorphisms (RFLPs) were used to assess genetic diversity of mitochondrial DNA (mtDNA) among standard isolates of seven lineages of Fusarium graminearum. The mtDNA patterns within each lineage were very similar (>89%), whereas significant differences were observed between the isolates belonging to different lineages, with the exception of lineages 1 and 4 where strong similarity was found between the RFLPs. Analysis of different band patterns resulted in characteristic HhaI and HaeIII bands that were suitable for identification of members of lineages 7, 6, 5, 3 and 2. Investigation of lineage distribution of 144 European isolates revealed that 142 belong to lineage 7. These data, therefore, confirmed the hypothesis that members of lineage 7 are predominant in Europe. Further analysis of isolates belonging to lineage 7 resulted in five haplotypes. These haplotypes have arisen as different combinations of three RFLP patterns for both HaeIII and HhaI restriction enzymes. Two isolates from Hungary, however, shared the same mtDNA RFLP profiles with a standard isolate of lineage 3, indicating that members of lineage 3, at a lower frequency, may also occur in Europe. Introduction Fusarium graminearum (teleomorph Gibberella zeae) causes serious foot rot and head blight dis- eases of small-grain cereals, grasses, and ear and stalk rot of maize (Snijders, 1990; Bottalico, 1998). Severe Fusarium head blight (FHB) epidemics have been reported in the United States (McMul- len et al., 1997), Europe (Bottalico, 1998) and East Asia (Chen et al., 2000). Grain is often contami- nated with trichothecene and oestrogenic myco- toxins, making it unsuitable for food and feed (Bottalico, 1998). Investigation of the global diversity of F. graminearum based on the DNA sequence of six single-copy nuclear genes has revealed the exis- tence of seven distinct phylogeographic lineages that appear to be reproductively isolated (O’Donnell et al., 2000). Because each lineage is represented by two to seven isolates only, addi- tional data is needed to further characterise the geographic distribution of the seven F. graminea- rum lineages. In the work of Gale et al. (2002), 225 isolates of F. graminearum from wheat were investigated using restriction fragment length polymorphisms (RFLPs). Diagnostic RFLP markers established that all isolates belonged to F. graminearum lineage 6 (‘Asian clade’). Lineage 7 is geographically more widespread and appears to be the dominant or sole lineage found in the Ameri- cas and in European countries (‘Pan-Northern Hemisphere clade’), but to date there are limited data on lineage distribution of F. graminearum isolates. The phylogeographic lineages of F. graminea- rum cannot be differentiated on the basis of mor- phological traits. Gale et al. (2002) identified nuclear DNA fragments that could be used for developing diagnostic RFLP markers for identifi- cation of F. graminearum lineages. Mitochondrial European Journal of Plant Pathology 110: 545–550, 2004. Ó 2004 Kluwer Academic Publishers. Printed in the Netherlands.