Purification of the Phytoplasma Associated with China‐tree (Melia azedarach L.) Decline and the Production of a Polyclonal Antiserum for its Detection

China‐tree or paraiso ( Melia azedarach ) decline, caused by a phytoplasma, is a disease in Argentina for which hitherto no diagnostic reagents were available. The production of a polyclonal antiserum using a purification protocol involving a double Percoll gradient is reported. The antiserum was used successfully in immuno‐dot blot assay to discriminate between infected and healthy plants. It also recognized, although less reliably, other phytoplasmas present in garlic ( Allium sativum ), peach ( Prunus persica ) and tona ( Tona cilliata ). Organisms that by their size and morphology resembled phytoplasmas were detected by immuno‐electron microscopy and immunogold labelling. The ability of the antiserum to discriminate between healthy and infected plants was confirmed by PCR amplification of fragments only from infected plants.