Molecular Detection And Identification Of Four Phytoplasmal Diseases

The phytoplasmas associated with chaste tree witches'-broom, Rosa multiflora Witches'-broom, Dragon juniper yellows, Purpus Privet dieback, and Japan Euonymus yellows were identified.The main results are as follows:The symptoms of chaste tree witches'-broom (CTWB) included stunting, yellowing, witches'-broom and dieback.The disease was graft-transmissible. Phytoplasma cells were observed in diseased phloem under electron microscopy. The 16S rRNA gene of the phytoplasma associated with CTWB was amplified with nested-PCR.The amplified fragment was sequenced and subjected to identity and phylogenetic analyses.CTWB shared identities of more than 99.0% with members of Aster yellows group (16SrI) in 16S rRNA genes. It had the highest identity of 99.8% with phytoplasmas associated with Maize bushy stunt (subgroup 16SrI-B), and formed a common branch with phytoplasmas of that subgroup in the phylogenetic tree constructed with 16S rRNA genes. These results indicated that phytoplasma associated with CTWB belonged to subgroup B of Candidatus Phytoplasma asteris (16SrI-B).A specific fragment of ca. 1.2 kb in length was amplified with PCR from Rosa multiflora plants with typical witches'-broom symptom. The fragment was sequenced and subjected to RFLP and phylogenetic analysis. The results showed that the phytoplasma associated with Rosa multiflora witches'-broom belonged to 16SrI-B subgroup.Phytoplasma-specific fragments of ca. 1.2kb in length were amplified by nested-polymerase chain reaction from samples of dragon juniper showing yellows and Purpus Privet plant with dieback symptom. RFLP and phylogenetic analysis showed that the phytoplasmas associated with these diseases belonged to 16SrI-B subgroup.This is the first report of chaste tree witches'-broom, Rosa multiflora witches'-broom, dragon Chinese juniper yellows, purpus privet dieback.in China.