Population development within the coffee wilt pathogen Gibberella xylarioides reflects host-related divergence

Variation of 45 Gibberella xylarioides cultures isolated from coffee trees in Africa was assessed by sequencing the partial translation elongation factor gene, by A + T rich DNA restriction fragment length polymorphism (RFLP) analysis and by inter-simple sequence repeat polymerase chain fingerprinting. Results were analysed in relation to host plant species and mating compatibilities to determined biological species (BS). Additionally, five “historical” strains isolated prior to the 1990s, and considered to belong to G. xylarioides , were obtained from internationally-recognised culture collections and a further 10 strains of various Gibberella / Fusarium spp., isolated from Coffea spp., were included to provide contextual comparisons. Ribosomal intergenic spacer (IGS) sequencing was undertaken for representatives of the suggested BS. Results confirmed all strains as G. xylarioides and that strains of sterile group 4 (SG4) may represent one or more additional “cryptic” species. ISSR fingerprints showed a single host correlated difference, suggesting stable clonal spread and this was supported by consistent A + T rich DNA band patterns for all strains. In contrast the IGS sequences identified potential phylogenetic events correlated to BS.