Host-related variation among isolates of the Sirococcus shoot blight pathogen from conifers

Summary Variation among isolates of the Sirococcus shoot blight pathogen (attributed to Sirococcus conigenus, Sirococcus sp., or one of many synonyms) was studied. Inter-simple-sequence-repeat-anchored polymerase chain reaction fingerprints, nuclear rDNA internal transcribed spacers and 5.8S sequences, and 18S rDNA sequences were analysed. In addition, culture morphology as well as sizes and shapes of conidia produced on seed cone scales in culture were compared. Two main groups were distinguished based on both genetic markers and cultural characteristics. The P group consists of isolates mostly from pine and spruce from Europe and both eastern and western North America; the T group consists of isolates mostly from hemlock from western North America. Results provide a benchmark for comparison of other isolates of these fungi and indicate the need for additional sampling and comparative research of these pathogens. Resume L’etude porte sur la variabilite entre isolats de Sirococcus (Sirococcus sp., S. conigenus, et nombreux synonymes), agent de dessechement de pousses. Des empreintes moleculaires obtenues par amplification de sequences encadrant des motifs microsatellites (ISSR) ainsi que les sequences de l'ITS, 5.8S et 18S de l'ADN ribosomal nucleaire ont ete analysees. De plus, la morphologie culturale ainsi que la forme et la taille des conidies produites sur ecailles de cones en culture ont ete comparees. Deux groupes principaux ont ete definis sur la base des marqueurs genetiques et des caracteristiques culturales. Le groupe P est constitue d'isolats provenant majoritairement de pin et epicea d'Europe et de l'ensemble de l'Amerique du Nord, Est et Ouest; le groupe T est constitue d'isolats provenant majoritairement de Tsuga d'Amerique du Nord-Ouest. Ces resultats constituent une reference pour la comparaison d'autres isolats de ces champignons et montrent la necessite d'un echantillonnage plus large et d’etudes comparees sur ces pathogenes. Zusammenfassung Es wurde die Variation zwischen Isolaten des Erregers des Sirococcus- Triebsterbens (benannt als Sirococcus conigenus, Sirococcus sp. oder eines von vielen Synonymen) anhand folgender Marker untersucht: ISSR-PCR-Fingerprints, ITS, 5.8S und 18S Sequenzen der nuklearen rDNA. Zusatzlich wurde die Kulturmorphologie sowie die Grosse und Form von Konidien, die auf Zapfenschuppen in Kultur gebildet wurden, erfasst. Aufgrund der genetischen Marker sowie der Kulturmorphologie liessen sich zwei Hauptgruppen unterscheiden: Die P-Gruppe besteht vorwiegend aus Isolaten von Kiefern und Fichten aus Europa und aus dem Westen und Osten Nordamerikas, die T-Gruppe besteht hauptsachlich aus Isolaten von Tsuga aus dem westlichen Nordamerika. Diese Ergebnisse bilden eine Vergleichsbasis fur weitere Isolate aus dieser Pilzgruppe und zeigen, dass weitere Untersuchungen dieser Pathogene notwendig sind.

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