Isozyme Variation and Species Delimitation in the Ceratocystis coerulescens Complex

Nineteen electrophoretic phenotypes (unique combinations of electromorphs) were found among 98 isolates of Ceratocystis coerulescens and morphologically similar species using 10 isozymes. Analysis of the isozyme data and morphological comparisons suggested that there are five variants of C. coerulescens found on conifers: three are associated with blue-stain of Picea or Pinus, one (C. coerulescens f. douglasii) with blue-stain of Pseudotsuga, and one associated with the bark beetle Dendroctonus rufipennis on Picea. Ceratocystis polonica and C. laricicola, associated with bark beetle species in the genus Ips on Picea and Larix, respectively, had similar isozymes, are morphologically indistinguishable from each other, and should probably be synonymized. Ceratocystis virescens, cause of stain of hardwoods and sapstreak disease of Acer saccharum, is distinct from the conifer species of Ceratocystis in isozyme electromorphs and anamorph morphology. Isozymes of C. virescens show some similarity to those of two Australian species, an undescribed species of Ceratocystis from Eucalyptus and Chalara australis. The Chalara states of these three hardwood species and Chalara neocaledoniae are morphologically similar.