Diversity And Vector Transmission Characterization Of Praxelis Witches’ Broom Phytoplasma

Praxelis clematidea, as one of seriously invasive weeds, invades farmland, forests, not only causes bad effect on economy, also threatens diversity of eco-environment in Hainan. Up to now, there is no methods good enough to control it. Thus, the research on how to use Praxelis clematidea witches’broom as a biotic-control method is very important.In this survey, we investigated the status of Praxelis clematidea witches’broom in Hainan, primed the genetic sequence of16SrDNA of phytoplasma in Praxelis clematidea witches’broom through polymerase chain reaction (PCR) and Nested-polymerase chain reaction using universal primers P1/P7and R16F2n/R16R2respectively, identified the vector of phytoplasma in Praxelis clematidea witches’broom, and tested its characterization of vectoring phytoplasma.The general results show that:(1) Praxelis clematidea has presented in all kinds of habitats in every town of Hainan, and formed advantage community mainly in roadside, slope land, grassland, and artificial forests with lower canopy density. Praxelis clematidea witches’broom exists in many habitats in Hainan. The disease incidence ranges from0.37%to3.01%, and disease index ranges from0.31～2.59. The height of Praxelis clematidea infected by witches’broom is as only33.3%～63.5%as that of the healthy, which indicates that Praxelis clematidea witches’broom can depress the growth of Praxelis clematidea.(2) One sequence fragment as1248bp long as other reported phytoplasmas was primed by Nested-PCR from the DNA extracted from Praxelis clematidea infected by witches’ broom, and from aphides. Through transmission test, aphid was determined as the vector of pathogen of Praxelis clematidea witches’ broom.(3) The patterns of restriction fragment length polymorphism analysis of16SrDNA sequence primed from phytoplasma associated with Praxelis clematidea witches’broom and peanut witches’broom are basically same, which indicates that phytoplasma associated with Praxelis clematidea should arrange to16SrRNAⅡ-A group.(4) Sequencing the gene of phtoplasma associated with Praxelis clematidea witches’ broom, and comparing it with sequences of other phytoplasmas, the result was basically as same as RFLP. The homology index between Praxelis clematidea witches’broom-phtoplasma and phtoplasmas of16SrRNAⅡ-A group are all over90%, which indicates Praxelis clematidea witches’broom-phtoplasma really belongs to involving branch of16SrRNA Ⅱ-A group.(5) The transmission results show that, aphid could transmit Praxelis clematidea witches’broom-phtoplasma after a minimum acquisition-period of5minutes, after a minimum transmission-period of15minutes, and with a minimum amount of10individuals.To be concluded, this survey revealed phytoplasma is the pathogen associated with Praxelis clematidea witches’broom, identified its status in the Phylogenic tree and its vector, which supplied theoretical fundamental for searching an efficient biotic-control method.