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Peach (Prunus persica) is in many countries severely affected by yellows and decline diseases of phytoplasmal etiology. These diseases are caused by phylogenetically different phytoplasmas. X-disease is one of the most serious diseases of peach. It is widespread in North America and has not been observed elsewhere. This disease is induced by a distinct phytoplasma, the X-disease agent ‘Candidatus Phytoplasma pruni’, which is a member of the X-disease phytoplasma group or 16SrIII group, subgroup 16SrIII-A. ‘Ca. P. pruni’ is, at the level of 16S rDNA sequences, a homogeneous pathogen. Peach rosette, peach red suture, and peach yellows, also called little peach, are three other diseases which are mainly known from eastern North America. These diseases are currently of minor importance. They are also caused by the X-disease phytoplasma. Peach yellow leaf roll (PYLR) is a major disease of peach that occurs in California. The causative agent, the PYLR phytoplasma, is a member of the apple proliferation (AP) group and is most closely related to the pear decline phytoplasma. In Europe, peach is affected by an economically important disorder known as European stone fruit yellows. This disorder is induced by ‘Ca. P. prunorum’ which is a member of the AP group, subgroup 16SrX-B. ‘Ca. P. prunorum’ is closely related to other important temperate fruit tree phytoplasmas including the PYLR agent. In Lebanon and Iran, peach is affected by almond witches’-broom, a lethal disease that is induced by ‘Ca. P. phoenicium’. This phytoplasma is a member of the 16SrIX group, subgroup 16SrIX-B. Phytoplasmas of other phylogenetic groups, which are known to infect a wide range of plant hosts, have been identified in declining peach trees in several fruit growing areas worldwide. However, the pathological relevance of these non-peach phytoplasmas needs to be investigated in many cases.

The molecular identification and characterization of phytoplasmas infecting grapevine in four locations of different grape-growing regions of Serbia is reported. Samples from symptomatic and asymptomatic grapevine plants were collected during 2002 and 2003. Detection and identification of phytoplasmas were done by the restriction fragment length polymorphism analysis (RFLP) of polymerase chain reaction (PCR) amplified 16S rDNA. Grapevine yellows were associated with three molecularly distinguishable phytoplasmas. Flavescence dorée phytoplasmas (elm yellows group - 16SrV-C subgroup) were present only in the Župa Aleksandrovac region; in other surveyed regions Bois noir phytoplasmas (stolbur group - 16SrXII-A subgroup) were detected; a mixed infection of European stone fruit yellows (apple proliferation group - 16SrX-B subgroup) and Bois noir phytoplasmas was identified in one sample. A finer molecular characterization by the RFLP analysis on rpS3 and SecY genes of Flavescence dorée phytoplasmas from Župa Aleksandrovac allowed to verify that the Serbian genotype is indistinguishable from a strain from the Veneto region, Italy. Characterization performed on tuf gene of Bois noir phytoplasmas showed lack of amplification of samples from Erdevik. The identity of HpaII profiles on the tuf gene PCR products was observed between samples from Palić and Radmilovac, this pattern appears indistinguishable from one of the two profiles obtained in samples from the Italian grapevines used as reference strains.