| Phytoplasmas are a group of cell wall less, uncultured prokaryotes that obligated parasites of plant phloem tissue and transmitted by phloem-feeding insects, mainly leafhopper and psyllids. It associated with thousands of plant disease in the world, and above one hundred in China. The research here detected and identified four phytoplasma diseases found in Guanzhong, Shaanxi Province using molecular biology techniques and electron microscope. The main finding are as follow:1)We collected clove leaves with symptoms of leaf roll from Xi'an, Xian yang, Bao ji and Yang ling, Shaanxi Province and found phytoplasma bodies localized in the phloem cells of clove mid leaf with electron microscopy. We speculated the disease was caused by phytoplasma.16S rRNA gene was cloned and used for phylogenetic and RFLP analysis. According to the results, we classified the phytoplasma in clove with symptom of leaf roll into subgroup 16Sr I-B. And phytoplasmas in cloves collected from Xi'an, Xian yang, Bao ji and Yang ling could be condidered as the same one.2)1.2 kb fragment was amplified from clover with symptoms of phyllody and petiole enlargement. Sequencing results certified the pathogen was phytoplasma. RFLP and phylogenetic analysis follow revealed the phytoplasma caused clover phyllody in China was a member of 16SrV-B. Comparasion with sequences of other phytoplasma strains in Genbank showed the phytoplasma shared 99.6% homology with Jujube witches' broom (JWB) FJ154844, a represent strain of 16SrV-B.3)Berberis phyllody disease caused virescence of young leaves and phyllody.16S rRNA gene was cloned and used for RFLP and phylogenetic analysis. It showed highest homology 99.8% and clustered one branch in phylogenetic tree with JWB phytoplasma. Combined with the collective patterns of RFLP digestion, we confirmed the phytoplasma was a member of 16SrV-B and had a close relationship with JWB phytoplasma. For the first time we confirmed Berberis phyllody disease was a phytoplasma disease and described the molecular characteristics of the phytoplamsa.4)Phytoplasma universal primer pairs were adopted for 16S rRNA gene amplification by nested-PCR.1.2 kb length fragment was amplified from total DNA of spirea sample with yellowing symptom. Sequencing results revealed the phytoplasma in yellowing spirea should be classified into 16SrV-B subgroup.Berberis phyllody and clove leaf roll diseases are reported for the first time in the world, while spirea yellowing and clover phyllody diseases in China. |
