Phenotypic And Genotypic Structure Of Phytophthora Infestans Population From Tomato In Hebei Province

Tomato late blight caused by Phytophthora infestans is one of the most devastating diseases in tomato production. The phenotype of 49 isolates collected in Baoding, Cangzhou and Tangshan cities of Hebei province during 2007 and 2008 were investigated for mating types and metalaxyl and metalaxyl-M resistance. The genotypes were also assessed for mitochondrial DNA haplotypes with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), simple sequence repeats (SSR) and amplified fragment length polymorphism (AFLP). At the same time, the preparation methods of the protoplasts from Phytophthora injestans were also studied. The results were as follows.1. Forty-nine isolates collected in Baoding, Cangzhou and Tangshan cities of Hebei province during 2007 and 2008 were investigated for mating types, the result showed that all the tested isolates were A1 mating type, and no isolate with A2 mating type was found.2. Forty-nine collected in Baoding, Cangzhou and Tangshan cities of Hebei province during 2007 and 2008 were investigated for metalaxyl resistance, the majorities were metalaxyl-sensitive and only seven isolates were metalaxyl-resistant. The EC50 values of the most insensitive strain was 100472 times of the the most sensitive strain.3. Forty-nine isolates collected in Baoding, Cangzhou and Tangshan cities of Hebei province during 2007 and 2008 were investigated for metalaxyl-M resistance, the number of strains with resistance, intermediate and sensitive to metalaxy were 3, 11 and 35,the EC50 values of the most sensitive strain was 0.002μg/mL and the EC50 values of the most insensitive strain was 8.7843μg/mL.4.The mitochondrial DNA haplotypes were assessed with polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), the genotype of all the strains tested were Ia.5. The SSR genotype of the 49 isolates collected in Baoding, Cangzhou and Tangshan cities of Hebei province during 2007 and 2008 were tested with the eight pairs of SSR primer which compared with 5 Phytophthora infestans reference isolates on potato and 4 reference Phytophthora infestans reference isolates on tomato which collected from different provience. Three SSR genotypes were determined. type II SSR genotype was correlative to metalaxy resistance and geographical origin.6. The genomic DNA of 58 isolates were amplified with 6 selective primer combinations. A total of 258 AFLP bands were obtained, and 107 of them, covering 41.4%, showed polymorphism. The population genetic analysis indicated that the genetic diversity level of Phytophtora infestans population in Hebei was low, potato late blight pathogen and tomato late blight pathogen possessed host specificity. The seven AFLP sub-clades were not associated with metalaxyl resistance and geographical origin.7. Protoplasts of Phytophthora infestans were formed from mycelium, sporangia, and zoospores. The result showed the methods of preparing protoplasts from mycelium and zoospores were more ideality, the integral protoplasts were obtained.