DNA extraction from arborescent monocots and how to deal with other challenging hosts

Detection of pathogen DNA by polymerase chain reaction (PCR) assays is the most widely used method for diagnosing phytoplasma diseases. Reliable and efficient detection of phytoplasmas, especially in woody perennial plants, is challenging due to the unusually low abundance and sporadic distribution of phytoplasmas within infected host tissues. Detection success depends largely upon the host species and sampling procedures and, to a lesser extent, on the protocol used for DNA extraction. Here we describe a simple, straightforward, nondestructive stem sampling protocol to confirm phytoplasma infection of palms and other arborescent monocots of large stature. The protocol requires minimal processing of excised tissues and yields phytoplasma DNA preparations in suitable quantity for reliable detection by nested PCR assays.