Identification Of Pathogenic Species，Physiological Race And Biovar Of Major Tobacco Diseases In Jiangxi Province

There are many kinds of plant diseases found to infect tobacco presently in Jiangxiprovince, of which bacterial wilt, black shank and viral diseases occur most seriously. Inorder to ascertain the pathogenic species assignment and their physiological differentiationof main tobacco diseases in the province, and thus to provide theoretic basis for thebreeding and utilizing of disease-resistant tobacco varieties, pathogen of tobacco bacterialwilt, black shank and mosaic disease was identified by using a number of molecularbiological techniques including cDNA reverse transcription synthesis, polymerase chainreaction (PCR), target fragment cloning, and nucleotide sequencing in this study. Then,physiological race and biovar of pathogen of tobacco bacterial wilt and black shank wereidentified by using methods of inoculating differential host and biochemical reaction test.The results are as follows:(1) On the basis of determining the full length nucleotide sequence of16S rDNA gene(1500bp) and analyzing the homology, pathogen of tobacco bacterial wilt in Jiangxiprovince is identified as Ralstonia solanacearum. The differential host inoculation andbiochemical reaction results showed that Ralstonia solanacearum on tobacco in Jiangxibelonged to physiological race1, while in biovar division they belonged to biovar III-1. Itwas supposed that pathogenicity of the pathogen in Jiangxi were not significantlydifferentiated.(2) Based on sequencing and homology analysis of rDNA-ITS region, pathogen oftobacco black shank was identified as Phytophthora parasitica var. nicotianae.Biochemical test and differential host inoculation results indicated that all the testedisolates belonged to physiological race1.(3) By using gene cloning and sequencing, the complete nucleotide sequence of coatprotein (CP) gene of TMV、CMV、PVY was determined to be480bp,657bp and801bp,respectively. According to homology analysis of CP nucleotide sequence, the isolates ofCMV in Jiangxi province were classified in CMV subgroup I, whereas isolates of PVY inJiangxi were identified as strain N.(4) The phylogenetic tree showed that evolution and variation of Ralstoniasolanacearum, Phytophthora parasitica var. nicotiana, TMV, CMV and PVY on tobacco inJiangxi province were influenced by their geographical location, and not by their hosts.