A DNA-based method for detection ofPeridermium harknessii, the causal agent of western gall rust

Abstract

Peridermium harknessii is not present in the southern hemisphere yet it poses a serious threat to Pinus radiata cultivation in exotic forest plantations there. If a suspected incursion were to occur, it would be necessary to rapidly confirm the presence of P. harknessii within non-sporulating galls. With this in mind, we have developed a DNA-based identification system, using the first intergenic spacer region (IGS-1), that is able to detect the presence of the pathogen within galled tissue. The PCR primers are highly specific and with the exception of the closest relative, Cronartium quercuum f. sp. banksianae, they did not cross react with any of the 11 species within the closely related genera Cronartium and Peridermium that were tested. Phylogenetic analysis of the IGS-1 region confirmed that C. quercuum f. sp. banksianae is the closest relative to P. harknessii. The PCR primers and protocol reported here should prove useful in the event of a suspected western gall rust disease outbreak in exotic P. radiata plantations.