E. Torres¹*, S. Botti², S. Paltrinieri², M.P. Martin³ and A. Bertaccini²

¹ Laboratori de Sanitat Vegetal, DARP, Generalitat de Catalunya, Barcelona, Spain
² DiSTA, Patologia Vegetale, University of Bologna, Italy
³ Real Jardín Botánico, CSIC, Madrid, Spain

* aetorgu@correu.gencat.es

Accepted for publication 22/07/02

Symptoms of witches’ brooms and decline were observed on Spanish broom (Spartium junceum L.) in Catalonia, Spain (Fig. 1). The appearance of witches’ brooms which developed from axillary buds on this woody perennial shrub was followed by a drying of foliage. Affected plants eventually withered and died within a few years. A similar disease of S. junceum described in Italy was attributed to a phytoplasma etiology (Marcone et al., 1996).

Figure 1. Witches’ broom symptoms on a Spanish broom plant in Catalonia.

Samples from both affected and symptomless plants were analysed for phytoplasma infection by a nested polymerase chain reaction (PCR) assay employing rRNA primer pairs P1/P7 (Smart et al., 1996) followed by U5/U3 (Lorenz et al., 1995) or R16F2/R2 (Lee et al., 1995). An rDNA product of expected size (1.2 kb) was amplified by nested R16F2/R2-primed PCR from all nine symptomatic plant sample DNAs whereas no product was amplified from four symptomless plant samples. No products were obtained from either symptomatic or symptomless plants by nested U5/U3-primed PCR. R16F2/R2 products from two S. junceum plants (T-500 and T-701) were analysed further by reamplification of products by PCRs using nested 16S rRNA primer pair R16(V)F1/R1 or R16(X)F1R1 (Lee et al., 1995). An rDNA product (1.1 kb) was obtained from both plants with the latter apple proliferation phytoplasma (16SrX) group-specific primer pair only.

Figure 2. Phylogenetic tree constructed by parsimony analysis under heuristic search of 16S rRNA gene sequences from 46 phytoplasma strains and Acholeplasma palmae as the out group. Branch lengths are proportional to the number of inferred character state transformations. Bootstrap (confidence) values are shown on the branches. GenBank accession numbers for sequences are given in parentheses.

Identification and classification of S. junceum-infecting phytoplasmas as strains belonging to 16SrX group, subgroup D was determined by restriction fragment length polymorphism analysis of R16F2/R2-primed rDNA products using six endonuclease enzymes. Phylogenetic analysis of 16S rDNA sequences also delineated phytoplasma strain T-701 (EMBL accession no. AJ430067) as a 16SrX group strain most closely related to the phytoplasma associated with Spartium witches’ broom in Italy (Fig. 2). This is the first report of a phytoplasma disease of S. junceum in Spain.

Lee I-M, Bertaccini A, Vibio M, Gundersen DE, 1995. Detection of multiple phytoplasmas in perennial fruit trees with decline symptoms in Italy. Phytopathology 85, 728-735.

Lorenz K-H, Schneider B, Ahrens U, Seemüller E, 1995. Detection of the apple proliferation and pear decline phytoplasmas by PCR amplification of ribosomal and nonribosomal DNA. Phytopathology 85, 771-776.

Marcone C, Ragozzino A, Schneider B, Lauer U, Smart CD, Seemüller E, 1996. Genetic characterization and classification of two phytoplasmas associated with Spartium witches’ broom disease. Plant Disease 80, 365-371.

Smart CD, Schneider B, Blomquist CL, Guerra LJ, Harrison NA, Ahrens U, Lorenz K.-H, Seemüller E, Kirkpatrick BC, 1996. Phytoplasma-specific PCR primers based on sequences of the 16-23S rRNA spacer region. Applied and Environmental Microbiology 62, 2988-2993.

The British Society for Plant Pathology