Identification of phytoplasma belonging to X-disease group in cherry in Chile.

Abstract

Abstract During summer 2006 sweet cherry ( Prunus avium L.) trees, exhibiting disease symptoms suggestive of possible phytoplasma in-fection were observed in the Libertador General Bernardo O’Higgins region of Chile. Branches were collected from ten plants (five with and five without symptoms) and nucleic acid extracted from leaf midribs and phloem scrapings was used for phyto-plasmas testing. Nested polymerase chain reaction (PCR) amplification allows the detection of phytoplasmas in samples from plants that showed symptoms, but not in those from asymptomatic ones. Restriction fragment length polymorphism, cloning, and sequencing allowed identification of phytoplasmas into ribosomal subgroup 16SrIII-J. Key words: cherry, nested-PCR, phytoplasmas, RFLP, sequencing. Introduction Production of sweet cherry ( Prunus avium L.) in Chile is concentrated in three regions: Libertador General Bernard O'Higgins (VI), Maule (VII) and Bio-Bio (VIII) and the fruit is for fresh consumption or for processing. In one orchard located in the VI region a decay, low vigor and even death of plants in the variety Basler Langstieler (for processing), especially when grafted onto the rootstock Colt, were observed. The symptoms appear on plants of at least three years: the vigor reduc-tion has been moderate to strong, and in most cases, removing the bark, phloem necrosis was observed in trunk or branches. No fungal or bacterial isolation was obtained. Through the observation of symptoms phytoplasma presence was suspected and molecular analyses were carried out both in healthy and symptomatic plants to verify the presence of these prokaryotes.