First report of 'candidatus Phytoplasma asteris' from Gerbera jamesonii in Apulia, Southern Italy

Gerbera jamesonii, an economically crop in the Italian cut flower market is reported to be affected by phytoplasmas of two 16S ribosomal groups from different parts of the world: 16SrII from Australia (Siddique, 2005), and 16SrI from Italy (Bertaccini and Bellardi, 1998). Gerbera plants with virescence, phyllody and abnormal flower colour, indicative of phytoplasmal infection, were observed in Apulia (southern Italy) in January 2010. Disease incidence was near 100% in cv. Maxima while no apparent symptom were seen in cv. Fuego. For phytoplasma detection, total DNA was extracted from the leaves of three symptomatic and one symptomless plant of each cultivar and used in nested PCR with primers P1/P7 (Schneider et al., 1995) and R16F2/R2 (Lee et al., 1993). DNA fragments of 1.2 kb, corresponding to 16S rDNA, were amplified only from DNA of the three symptomatic samples. When digested with MseI, amplicons showed identical RFLP patterns, which were indistinguishable from those produced by the European aster yellows strain of the "Candidatus Phytoplasma asteris". The 1,803 bp amplicon from P1/P7 PCR amplification was cloned into pGEM vector, and plasmid DNAs from two transformed clones were sequenced (BioFab Research, Italy). Both clones showed the same sequence (GenBank accession No. JF795864) and ClustalW2 alignment confirmed that 16S rDNA of gerbera phytoplasma shared 99.9% identity with Oenothera phytoplasma 86-7 [GenBank accession No. M30790; Lim and Sears (1989)], and 99.0% identity to several "Ca. P. asteris" isolates of different ribosomal subgroups (A, B, D, E, F, K, and P. GenBank accession Nos. HQ589187, EF634457, AY265206, AY265213, AY265211, U96616, AF503568, respectively). "Ca. P. asteris" is widely spread in Italian cut flower crops but this is its first report from gerbera in Apulia.