The Identification Of The Pathogen Of Tobacco Root And Stem Fungal Diseases And The Physiological Race Of Phytophthora Parasitica Var. Nicotianae In Henan

In order to identify the species of tobacco root and stem fungal diseases and thephysiological race of phytophthora parasitica var. nicotianae in Henan province, weinvestigated in15tobacco-growing areas of Dengfeng, Dengzhou, Jiyuan and so on.The pathogens were isolated and purified with the method of tissue separation, and thepathogenicity of one’s were determined by Koch’s postulates, the taxonomic status wasidentified based on the morphological characteristics and the sequence of rDNA-ITS.Then, we identified the physiological race of p. parasitica var. nicotianae, which wereisolated from all the15areas in Henan, by the differential hosts and the reaction ofTTZ.(1) According to the field investigation, the symptomatic diagnosis and theidentification of pathogens, we testified the pathogen of tobacco southern blight isSclerotium rolfsii Sacc, and of tobacco gray mold is Botrytis cinerea Per. et Fries, oftobacco brown spot is Alternaria alternate (Freis) Kissler.(2) The morphological characteristics and the sequences of rDNA-ITS and thepathogenicity identification showed the pathogen of tobacco black shank isphytophthora parasitica var. nicotianae (Breda de Hean) Tuker, of tobacco damping-offare Pythium aphanidermatum (Edson) Fitzpatrick and Pythium vexans de Bary, oftobacco root rot is always shows Fusarium solani (Martius) App. et Wr and tobaccofusarium wilt is always shows Fusarium oxysporum Schlecht, of tobacco lowerblack-head is Colletotrichum capsici (syd) Butler&Bisby, of tobacco anthracnose isColletotrichum gloeosporioides (Penz.) Sacc, of tobacco ascochyta stem wilt isDidymella ligulicola (K. F. Baker, Dimock&L. H. Dacis) von Arx(anamorph:Ascochyta chrysanthemi F. L. Stevens), of tobacco phoma disease is Phoma sp., oftobacco phomopsis stem wilt is Phomopsis sp.. To be sure, the tobacco ascochyta stem wilt and the tobacco phomopsis stem wilt are all the new diseases of tobacco, and the P.vexans de Bary is the new pathogen of tobacco damping-off, and the tobacco phomadisease is the first report in Henan.(3) We have acquired36strains of P. parasitica var. nicotianae in the15tobacco-growing areas in Henan, and the results of the two methods of identificationshowed that the race1is the dominated race, accounts for88.9%of the36strains. Butthe rest of four strains showed different reaction on the hosts: one strain is resisted byL8, two strains are weak pathogenic to it, one strain has no pathogenic to NC1071, thesefour strains cannot be determined at present.In this study, tobacco root and stem fungal diseases are further identified based onthe morphological characteristics and the sequences of rDNA-ITS. The results showed anew pathogen each of tobacco damping-off and tobacco phoma disease, and came upwith two new diseases, which were tobacco ascochyta stem wilt and tobacco phomopsisstem wilt. In addition, the race1is identified as the dominated race of P. parasitica var.nicotianae in Henan. This study will provide theory evidence on the accurate diagnosisand effectively prevent of the tobacco disease.