The Screening Of Tobacco Germplasm Resources For Resistance To Potato Late Blight

Potato(Solanum tuberosum) is the fourth crop in the world. Late blight, caused by Phytophthora infestans de Bary, is the most destructive disease. Nonhost resistance is an important type of plant disease resistance which governs defense responses to a broad spectrum of potential pathogen species. The nonhost resistance is more effective and durable resistance than host resistance in plant. Nicotiana tabacum is belong to Solanaceae plants as Solanum tuberosum. It was reported as non-host plant for Phytophthora infestans de Bary.In this study, we have screened out of potato late blight resistance varieties from a resource populations of tobacco, and characteration of different types of resistance and susceptible varieties which will help to clone the resistance genes by using combinated methods of genetic and molecular biology. Futher, these genes will provide as a resistance resource stock for potato breeding.By using Nicotiana tabacum and Phytophthora infestans as a nonhost plant-oomycete interaction system, we tested340species tobacco germplasm resources our laboratory own with six P. infestans isoltates with detached leaf method. The selected results can be divided in five phenotype:the susceptible species、the species with yellow and watermarks、the species with infection spot、the species with yellow、the disease-resistant species, one clones、 ten clones、six clones、eight clones and three hundred and fifteen clones respectively. We stained part species of four kind phenotypes with trypan blue, the susceptible species(Nicotiana glutinosa) can be observed lots of hyphae, the species with yellow and watermarks、the species with yellow can be observed a few of hyphae, the species with infection spot can be observed HR response.After inoculated Phytophthora infestans isolates at different seedling ages of3or4,7or8leaves Nicotiana glutinosa,we found that the susceptible sympton was decreased as the leaf age increase. Results indicated that this type of nonhost resistance is age-dependent. Also, this age-dependent resistance suggested to test the inoculation system better at3or4leaves age.The methanol extracts from leaves of the tobacco、benthamian、tomato、potato were examined for antibacterial activity on potato late blight. This suggested that nonhost resistant to P. infestans was not assoiciated with the secondary metabolic products.Crossing between the susceptible species(Nicotiana glutinosa) and some selected resistance varieties, we generated F2populations which lay a foundation to map and clone the R genes in the future.In general, we set up a nonhost plant-oomycete interaction system between Nicotiana tabacum and Phytophthora infestans with detached leaf assay. And chactered24partial susceptible varieties and1completely susceptible variety, which available to clone the nonhost R gene, Also, we excluded that this nonhost resistance directly related to plant metabolic products, provide evident to support the caused agent with mainly R gene as normal host resistance.