Variation in culture and rDNA among isolates of Sphaeropsis sapinea from Ontario and Manitoba

Abstract

Three morphotypes were recognized among Manitoba and Ontario isolates of Sphaeropsis sapinea. Variation in culture was assessed based on overall culture morphology, growth rates, and conidial characteristics. Morphotypes A and B conform to previously described morphotypes, but an intermediate morphotype with smooth conidia was designated as morphotype I. Morphotype A isolates were collected from a number of Pinus species as well as Picea pungens. Morphotype B was only recovered from Picea mariana on stressed sites in Ontario, and Pinus banksiana and Pinus resinosa in Manitoba. Morphotype I was recovered from Pinus species and Picea glauca. Restriction fragment length polymorphism analysis of the ribosomal repeat unit grouped the isolates into three classes, or ribotypes, which appear to correspond to the A, B, and 1 morphotypes. All three morphotypes have been collected in Ontario. Restriction fragment length polymorphism analysis of the rDNA repeat unit may therefore be useful in distinguishing Lhe different types of this tree pathogen and might be applied to assess the occurrence and distribution of the different morphotypes.

Keywords:

• Sphaeropsis
• diplodia
• morphotypes
• RFLP