The present paper was designed to elucidate the mechanism of the specificity of susceptpathogen interrelationships in potato-Phytophthora, with special reference to the DNA fraction of potato varieties and the races of Phytophthora infestans.
1. Hypersensitive flecks and susceptible lesions were observed on the resistant interspecific hybrid 96-56 by an inoculation of P. infestans (Race 0) after applying the the crude sap juice, DNA fraction and purified DNA extracted from the susceptible cultivar Norin No. 1.
2. Hypersensitive flecks and susceptible lesions were also observed on the resistant
interspecific hvbrid 96-56 by an inoculation of P. infestans (Race 0) after applying the DNA fraction (Elution No. 24) through Sephadex G 200 and RNA extracted from the susceptible cultivar Norin No. 1.
3. Ethanol, sodium chloride and Tris-buffer solution have no effect on the appearance of different types of fleck and lesions on potato midribs infected with P. infestans.
4. The appearance of different types of flecks and lesions on potatoes infected with P. infestans decreased by the treatment of DNA heated over 90℃.
5. Scions of resistant interspecific hybrid 96-56 on the stocks of susceptible cultivar Norin
No. 1 and vice versa showed susceptible lesions and hypersensitive flecks by an inoculation of P. infestans after grafting. Plants grown up from tubers obtained from grafted plants also showed susceptible lesions and hypersensitive flecks.
6. When the DNA fraction extracted from the mycelium of P. infestans (Race 1) was applied to the conidial suspension of P. infestans (Race 0) at 12℃ (indirect germination) and vice versa, the change of pathogenicity to the suscept was not observed.
7. The appearance of different types of flecks and lesions were not observed on the interspecific hybrid 96-56 by an inoculation of zoospores of P. infestans (Race 0) treated with DNA extracted from the susceptible cultivar Norin No. 1 for 1 hour.