Genetic Diversity Of The Super Physiological Race Of Phytophthora Infestans

The super physiological race could overcome all of the 11 resistance genes R1-R11, which would cause a great difficulties for resistant breeding and the management of late blight disease on potato planting. In this research, the analysis of the genetic diversity of the super physiological race in Phytophthora infestans could reveal its rule of genetic variation and character, which would give the directions for the strategy of resistant varieties breeding and the management of late blight disease on potato planting.1. The results showed that 21 strains were A1 mating type, 14 self-fertile and only 5 A2 mating type among the 40 tested isolates of the super physiological race. The numbers of high resistant and sensitive isolates to metalaxyl were 26 and 14, respectively.2. By using an in vitro radial growth assay, virulences of two fungicides （azoxystrobin and fluopicolide-propamocarb） to super physiological race were measured. The result showed that the EC50 values of azoxystrobin and fluopicolide-propamocarb in 40 field isolates of super physiological race were 0.07-0.22μg·mL^-1 and 2.05-4.75μg·mL^-1, respectively. This shows that super physiological race were remain susceptible sensitive to both azoxystrobin and fluopicolide-propamocarb.3. Different super physiological race isolates had inequable infecting potential and the disease index between 1-4. That suggests the most complex strains did not receive more aggressive.4. The mtDNA haplotypes of all the 40 super physiological race were assessed with polymerase chain reaction-restriction fragment length polymorphism （PCR-RFLP）, the test showed a nearly 1-to-1 ratio betweenⅠa andⅡa.5. Among 40 isolates of the super physiological race, 16 SSR genotypes were identified and nominated by use of ten loci （contain five international common SSR loci and five other SSR loci have been independently developed by my laboratory ）.6. The 6 fluorescence labeled AFLP primers generated 204 polymorphic bands within a total of 258 bands and revealed 72% polymorphism and could differentiate almost all of 40 isolates. In total, the phenotypic and genotypic data indicated that the genetic diversity of the super physiological race was very rich and complex.