title: Assessment of diversity and genetic relationships ofNeonectria ditissima: the causal agent of fruit tree canker.
abstract: BACKGROUND
  Neonectria ditissimais one of the most important fungal pathogens of apple trees, where it causes fruit tree canker. Information about the amount and partitioning of genetic variation of this fungus could be helpful for improving orchard management strategies and for breeding apple cultivars with high levels of genetically determined resistance. In this study single-sporeNeonectriaisolates originating from both the same and from different perithecia, apple cultivars and apple orchards in Sweden and Belgium, were evaluated for AFLP- and SSR-based genetic similarity and for mating system.
  
  
  RESULTS
  Seven SSR loci produced a total of 31 alleles with an average of 4 alleles per locus, while 11 AFLP primer combinations produced an average of 35 fragments per primer combination and 71 % polymorphic fragments. An AFLP-based analysis of molecular variance (AMOVA) revealed that 89 % of the variation was found within orchards and 11 % between orchards. Genetic similarity among the studied isolates was illustrated with a principal coordinate analyseis (PCoA) and a dendrogram. AFLP-based Jaccard's similarity coefficients were the highest when single-ascospore isolates obtained from the same perithecium were compared, medium-high for isolates from different perithecia on the same tree, and lowest when isolates from different trees were compared.
  
  
  CONCLUSIONS
  Based on the results of PCoA and AMOVA analysis, isolates from the same or geographically close orchards did not group together. Since AFLP profiles differed also when single-ascospore isolates from the same perithecium were compared, the mating system ofN. ditissimais most likely heterothallic.
authors.affiliation: Department of Plant Breeding, Swedish University of Agricultural Sciences, Box 101, 230 53 Alnarp, Sweden.
authors.forename: Marjan
authors.identifier: 0000-0002-0600-2475
authors.initials: M
authors.lastname: Ghasemkhani
authors.affiliation: Department of Plant Breeding, Swedish University of Agricultural Sciences, Box 101, 230 53 Alnarp, Sweden.
authors.forename: Larisa
authors.initials: L
authors.lastname: Garkava-Gustavsson
authors.affiliation: Department of Plant Protection Biology, Swedish University of Agricultural Sciences, Box 102, 230 53 Alnarp, Sweden.
authors.forename: Erland
authors.initials: E
authors.lastname: Liljeroth
authors.affiliation: Department of Plant Breeding, Swedish University of Agricultural Sciences, Balsgård, Fjälkestadsvägen 459, 29194 Kristianstad, Sweden.
authors.forename: Hilde
authors.initials: H
authors.lastname: Nybom
mesh_terms: D000483:Alleles; D054458:Amplified Fragment Length Polymorphism Analysis; D001530:Belgium; D004271:DNA, Fungal / Q000235:genetics; D005819:Genetic Markers; D014644:Genetic Variation; D005828:Genetics, Population; D006999:Hypocreales / Q000235:genetics*; D027845:Malus / Q000382:microbiology*; D018895:Microsatellite Repeats; D010935:Plant Diseases / Q000382:microbiology*; D013548:Sweden; D014197:Trees / Q000382:microbiology*
chemical_list: D004271:DNA, Fungal; D005819:Genetic Markers
keywords: AFLP; Apple canker; Genetic variability; Heterothallism; Mating system; SSR