Association of Candidatus Phytoplasma asteris with little leaf disease of desert rose

Abstract

Desert rose ( Adenium obesum ) of the Apocynaceae family, is an exotic ornamental plant from warm climates, grown for its attractive fleshy stem, leaves and bright colourful flowers. Little leaf-like symptoms were observed in May‐August 2006 on two plants being maintained in a house garden at Lucknow, India. Symptoms included phyllody and excessive development of internodes resulting in little leaves. To assay for the association of phytoplasma with the little leaf symptoms, total DNA was isolated from infected leaf tissues and from an apparently healthy plant. PCR was performed with P1/P6 universal primers specific to the 16S rRNA gene (Deng & Hiruki, 1991). In addition, nested PCR was carried out with primers R16F2n/R16R2n (Gundersen & Lee, 1996) using the first round PCR product as the template. DNA fragments of the expected sizes (~1·5 kb and 1·2 kb respectively) were obtained from the infected plant samples but not from the apparently healthy one. The identity of the PCR amplicons was confirmed by Southern blot hybridization using a probe prepared from a clone of the chilli little leaf phytoplasma reported earlier (GenBank Acc. No. DQ343288), which showed strong hybridization under high stringency conditions. The 1·2 kb amplicon was sequenced and the sequence data deposited in GenBank Acc. No. EF159729. The sequence shared 99% similarity with the 16S ribosomal RNA gene of Barley deformation, Aster yellows,