This paper deals with the response of potato tuber and leaves invaded by Phytophth ora infestans, with special reference to the application of DNA fraction of resistant interspecific hybrid to the susceptible cultivars.
1) Potato tuber discs interspecific hybrid(R_1, R_4, R_1R_4 genes) and cultivars(r gene) were treated with the culture filtrate of P. infestans.(Race 0 and Race 1). Much more spots on the discs of interspecific hybrids having R gene were observed than those of cultivars having r gene 24 hours after the treatment of culture filtrate. Nature of the cuiture filtrate was examind by means of salting-out with ammonium sulfate and fractionation by organic solvents.
2) An increase in the brown spots was observed on the discs of the cultivar Benimaru which was applied with the DNA fraction of the interspecific hybrid 96-56 before treating with the culture filtrate of P. infestans. An increase in peroxidase activity was observed on the discs of cultivar Benimaru 3 hours after applied with the DNA fraction from interspecific hybrid 1506-b(9) before the treatment of the culture filtrate of P. infestans.
3) The amount of RNA in potato tubers (cultivar Benimaru) decreased 6-12 hours after inoculation of P. infestans. (Race 0), but the amount of RNA in the resistant interspecific hybrid 1506-b(9) increased 6-12 hours after inoculation. After treating with the DNA fraction from the interspecific hybrid 1506-b(9), the amount of RNA in the cultivar inoculated by P. infestans increased 3 times at 12 hours after inoculation compared with the cultivar Benimaru without the treatment of DNA fraction from the hybrid.
4) Rishitin was detected in the calli of the interspecific hybrid 1506-b(9) tuber infected with P, infestans but not detected in that of the cultivar Benimaru calli infected with the fungus or non-infected control plot. An amount of rishitin was recognized in the tuber of cultivar Benimaru treated with the DNA fraction from interspecific hybrid before the inoculation of P. infestans.
5) The conidial germination of P. infestans was inhibited in the water diffusate from the tuber of the interspecific hybrid SH-469 on which P. infestans was inoculated for 9 hours.