Construction of a mitotic linkage map of Fusarium oxysporum based on Foxy-AFLPs

Construction of the first mitotic linkage map of the asexual fungus Fusarium oxysporum, based on a population of 32 parasexual fusion products, is reported. Molecular markers were developed using a modified AFLP technique which combines a Foxy-specific primer with standard adapter primers. The retroposon Foxy is abundantly present and highly variable in location in F. oxysporum isolates: 43% of the Foxy-AFLP markers tested appeared to be polymorphic between the strains Fol004 and Fol029. Of the 102 Foxy markers obtained, 83 segregated in a 1:1 ratio. The remaining fragments showed a skewed segregation pattern in which the Fol004 derived Foxy fragments were overrepresented. Foxy markers were observed to be clustered, suggesting that active Foxy elements may not transpose very far from their initial insertion sites, or that hotspots for insertion may exist. Linkage analysis revealed 23 linkage groups. Physical linkage between segregating markers predicted to be 20 cM apart was confirmed, indicating that the mitotic linkage map is reliable.