Study On Identification And Classification Of The Pathogen And Host Range Of Wheat Blue Dwarf

Wheat Blue Dwarf (WBD) caused by phytoplasma is first reported in China, which hasn't been reported in other countries.It is an important disease of winter wheat disseminated by Psammotettix striatus L. It often happens in semiarid and droughty regions of Northwest districts, which once happed in Shaanxi province for more than ten times, that caused economic losses in the wheat production. Economic losses range from partial reduction (20%～40%)in yield to nearly total crop loss. As the inability to culture phytoplasmas in vitro and their low content in plant tissue, moreover, the phytoplasmas can be transmitted only by leafhopper, for these reasons, the study on Wheat Blue Dwarf (WBD) was limited.In recent years, the phylogenetic position of phytoplasma of WBD has never been reported before, the primary infection and host range were only known a little, so, a systemic research was done to know more about Wheat Blue Dwarf, the results as following:The investigation on Wheat Blue Dwarf(WBD) in the field showed that:this disease was prevalent and serious in Shaanxi province, which resulted in large losses in yield. The occurrence of this disease is related to diseased plants, wheat variety, planting mode, density of insect vector and circumstances of wheat growth and so on, whereas, the enough diseased plants, susceptible wheat variety and high density of insect vector are very important for occurrence of Wheat Blue Dwarf disease. The pathogen and vector of Wheat Blue Dwarf(WBD) were identified according to the test of inoculation as well as the observation by electron microscope.No phytoplasma was found in the eggs of P. striatus L.,the results ascertained that they didn't disseminated the phytoplasma of Wheat Blue Dwarf .It's the first time to obseve the eggs of P. striatus L. by electron microscope.PCR assays were first used to amplified 16S rDNA and tuf gene(EF-Tu) of phytoplasma associated with Wheat Blue Dwarf(WBD),then sequenced the amplified fragments.The phylogenetic position of phytoplasma of WBD was determined by homology analysis of these sequence with those from typical phytoplasma in 16SrⅠsubgroup.The fragment amplified by primers R16mF2 /R16mR1 contained 1452 nucleotide, they had a high similarity on those of clover phyllody, the analysis result suggesed that the pathogen was in Aster yellows group (16SrⅠ),and 16SrⅠ-C subgroup, generally. In addition, the tuf gene fragment was 842 bp in length, which encoding 280 amino acids. Homology analysis for sequences of tuf gene...