Exposing the Enigma of Dothistroma Needle Blight Using Molecular Markers – a Progress Report

Abstract

Dothistroma septosporum is a fungal pathogen causing a disease known as either red band needle blight or Dothistroma needle blight (DNB) on Pinus species worldwide. The three morphological varieties of this pathogen originally recognized based on differences in conidial length (Thyr – Shaw 1964, Ivory 1967) have not been supported by DNA sequence analyses (Barnes et al. 2004). However, phylogenetic relationships of Dothistroma isolates from various countries, based on DNA sequences for portions of the rDNA ITS, β-tubulin and TEF 1-α gene regions, revealed that DNB is caused by two distinct fungal species (Barnes et al. 2004). One species, Dothistroma septosporum, has a world-wide distribution and a very wide host range (Barnes et al. 2004, Bradshaw 2004, Bednárová et al. 2006). It is the pathogen responsible for the devastating losses to pine plantations in many Southern Hemisphere countries (Gibson 1974). The teleomorph state of this fungus is Mycosphaerella pini (Funk – Parker 1966). In contrast, Dothistroma pini is known only from the non-native Pinus nigra in the North-Central U.S.A and from P. pallasiana plantations in Ukraine and South-Western Russia, outside the natural range of this pine species (Barnes et al. 2004, Barnes et al. 2007).