Detection and identification of 'Candidatus Phytoplasma prunorum'in Prunus germplasm

M J Rubio-Cabetas,S Sancho

doi:10.5424/sjar/2009072-1503

Abstract

The molecular characterization of the causal agent of diseases associated with several symptoms such as decline, yellowing,leaf roll and off-season growth in stone fruits made it possible to determine a common etiology, and the name ´European stone fruit yellows´ phytoplasma was proposed. Recently, the new taxonomical species description within the genus is 'Candidatus Phytoplasma prunorum'.A 2-yr survey was carried out in two different Prunus collections of the Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA) including European and Japanese plum genotypes of various species and several interspecific hybrids used as rootstocks. Both off-season growth in winter and decline were observed. In order to identify the phytoplasma suspected as a causal agent, two different PCR methods were applied to all inspected trees. The first method was a nested PCR with 16Sr X group-specific primers followed by RFLP analysis. Thesecond method was a direct PCR with specific primers for 'Ca P. prunorum' (Eca1/Eca2). In the most symptomatic treesthe presence of this phytoplasma was confirmed by at least one of the methods; negative results were obtained in asymptomatic trees. The nested PCR-RFLPs analysis was confirmed as a reliable method for routinary diagnosis rather than direct PCR.

Highlights

Several fruit species are affected by decline, yellowing, leaf curl, and floral virescence, diseases associated with phytoplasmas
In order to identify the phytoplasma suspected as a causal agent, two different PCR methods were applied to all inspected trees
European stone fruit yellows' (ESFY) was firstly described as a decline of Japanese plum in Italy (Goidanich, 1933) and it has been reported in several countries in Europe, as a serious problem in some Mediterranean countries, such as Spain (Sánchez Capuchino and Forner, 1973; Torres et al, 2004), France (Desvignes and Cornaggia, 1982; Jarausch et al, 1998), and Italy (Carraro et al, 1998), where apricot and Japanese plum, the most sensitive species, are widespread

Summary

Introduction

Several fruit species are affected by decline, yellowing, leaf curl, and floral virescence, diseases associated with phytoplasmas. These diseases include three economically important disorders of temperate fruit trees, 'pear decline' (PD), 'apple proliferation' (AP) and 'European stone fruit yellows' (ESFY). Until Lorenz et al (1994) determined the common etiology of these diseases and proposed the single name 'European stone fruit yellows' (ESFY), the disease had been designated according to the symptoms observed in stone fruit trees such as 'apricot chlorotic leaf roll' (ACLR) (Morvan, 1977), 'plum leptonecrosis' (PLN) (Giunchedi et al, 1978), and 'peach yellowing' (Poggi Pollini et al, 1993). These studies have shown the need for advancement in the detection methods for an early diagnosis of the phytoplasma diseases affecting stone fruits, avoiding the confused diagnosis often observed at very advanced status. A test was conducted to ascertain the reliability of both methods, with the aim of selecting the most adequate for routine diagnosis in a new collection where new rootstocks and cultivars should be planted

Material and methods

Results

Discussion