First report of Spartium witches’ broom disease in Spain

Abstract

Symptoms of witches’ broom and decline were observed on Spanish broom ( Spartium junceum ) in Catalonia, Spain. 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 aetiology (Marcone et al ., 1996). Samples from both affected and symptomless plants were analysed for phytoplasma infection by a nested polymerase chain reaction (PCR) assay employing rRNA gene primer pairs P1/P7 (Smart et al ., 1996) followed by U5/U3 (Lorenz et al ., 1995) or R16F2/R2 (Lee et al ., 1995). A PCR product of expected size (1·2 kb) was amplified by nested R16F2/R2-primed PCR from all nine affected plant sample DNAs, whereas no product was amplified from four symptomless plant samples. No products were obtained from either plants with or without symptoms 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 PCR using nested 16S rRNA gene primer pair R16(V)F1/R1 or R16(X)F1R1 (Lee et al ., 1995). A 1·1-kb product was obtained from both plants only with the apple proliferation phytoplasma (16SrX) group-specific primer pair. Identification and classification of S. junceum -infecting phytoplasmas as strains belonging to 16SrX group, subgroup D, were determined by restriction fragment length polymorphism analysis of R16F2/R2-primed rDNA products using six endonuclease enzymes. Phylogenetic analysis of 16S rDNA gene 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. This is the first report of a phytoplasma disease of S. junceum in Spain.