Detection and Identification of the Causal Agents of Dothistroma Needle Blight

Abstract

Dothistroma needle blight (DNB) is one of the most damaging foliage diseases of pine in plantations and natural forests worldwide and is caused by two closely related fungi: Dothistroma septosporum and D. pini, which are virtually impossible to differentiate from each other based on morphology. Although diagnosis of DNB based on symptoms is relatively reliable in the later stages of the disease when fruit bodies (conidiomata) are formed, for diagnosis in the early stages, as well as identification of the causal agent at species level, molecular methods are required. In addition, reliable and sensitive diagnostics before sporulation is a prerequisite for early detection to minimize accidental introductions of disease through movement of infected plant materials, especially seedlings. While amplification and sequencing of the ITS region of the rDNA alone is not reliable to differentiate the two species, conventional PCR (cPCR) using species-specific primers or mating type-specific primers and quantitative PCR (qPCR) are widely used and accepted molecular methods to identify and differentiate the DNB pathogens, either from cultures or directly from needles.