During field surveys in 1999 and 2000 of peach orchards in Northern‐Central Italy, plants of different cultivars were observed with symptoms of early leaf reddening, abnormal thickening of midribs and primary veins, autumnal growth of latent buds which produce tiny chlorotic leaves and sometimes flowers, and early phylloptosis; such symptoms, rarely seen previously on peach, are associated with European stone fruit yellows phytoplasma (ESFYP). In the orchards inspected, 1–4% of trees were affected and most were grafted on cv. G.F. 677. In most of the symptomatic samples (130 of 157 tested), only ESFYP was detected using different diagnostic methods [4′,6′‐diamidino‐2‐phenilindole, 2HCl (DAPI), polymerase chain reaction (PCR) with ribosomal and non‐ribosomal primer pairs, PCR‐enzyme‐linked immunosorbent assay, nested‐PCR]. The immunoenzymatic detection of PCR products with a pathogen‐specific probe ensured fast, sensitive and specific detection of ESFYP. This is the first survey to assess the occurrence of phytoplasmas in peach orchards in Northern‐Central Italy.

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Phytoplasmas were constantly detected by the DAPI technique and by PCR amplification of DNA from European plums (Prunus domestica) cv ‘Susina di Dro’ with symptoms similar to those reported for Japanese plum leptonecrosis. These symptoms included upward rolling of the leaves, which also became bronzed‐reddish, thick and brittle, growth of normally dormant axillary buds, off‐scason growth during November January and phloem necrosis. Trees with symptoms showed progressive decline. RFLP analysis, revealed that the phytoplasma isolated from the affected plum trees is closely related to the other phytoplasmas present in Prunus species in Europe and can be included in the apple proliferation cluster. Although Japanese plum leptonecrosis is common in Europe. this is the first report of a wide‐spread phytoplasma‐induced decline in a cultivar of European plum.

Polymerase chain reaction (PCR, with universal and specific primers designed on rRNA genes) provides a rapid, reliable method of diagnosing phytoplasmas (formerly mycoplasma-like organisms) in plants. However, to attain a better identification of these prokaryotes, it is often necessary to digest the PCR products with restriction endonucleases or to hybridize them with specific probes. The present study compared routine procedures for detecting PCR products against a new system, PCR-ELISA (Boehringer Mannheim), which enables immunoenzymatic detection of PCR products. The results show that this new system provides fast and highly sensitive detection of several phytoplasmas associated with certain trees and shrubs. Optimization of all parameters involved in the PCR-ELISA procedure and its advantages are reported and discussed. ZusammenfassungImmnnenzymatischer Nachweis von PCR-Produkten znr Idendfizierung von Phytoplasmen in Pflanzen Die Polymerase-Kettenreaktion (PCR, durchgeftihrt mit universellen und spezifischen, an rRNA-Genen erzeugten Primern) ist ein schnelles, zuverlassiges Verfahren zur Diagnose von Phytoplasmen (fruhere Bezeichnung: mykoplasmenahnliche Organismen) in Pflanzen. Um diese Prokaryonten besser identifizieren zu konnen, ist es jedoch oft notwendig, die PCR-Produkte mit Restriktionsendonucleasen zu spalten oder mit spezifischen Sonden zu hybridisieren. Die vorliegende Arbeit verglich Routineverfahren zum Nachweis von PCR-Produkten mit dem neuen System PCR-ELISA (Boehringer Mannheim), das eine immunenzymatische Detektion von PCR-Produkten ermoglicht. Die Ergebnisse zeigen, daB dieses neue System einen raschen und hochempfindlichen Nachweis verschiedener Phytoplasmen erlaubt, die mit bestimmten Baumen und Strauchem assoziiert sind. Die Optimierung aller Parameter der PCR-ELISA und die Vorteile des Verlahrens werden vorgestellt und diskutiert.

In the Sarca valley (Trento, north Italy) the presence of olive trees (Olea Europea L.) with yellow symptoms in a few branches was observed. Some leaves showed diffuse chlorotic mottling affecting almost all the blade, while others showed mottling with green and yellow areas: leaf deformation was also sometimes present. Phytoplasmas were only detected in olive trees with yellow leaves by polymerase chain reaction (PCR) amplification and subsequent restriction fragment length polymorphism (RFLP) analysis. The results obtained suggested a high similarity between this phytoplasma and the elm yellows phytoplasma. This is the first time that a phytoplasma has been reported in the genus Olea.