This paper deals with the results of invastigations on the application of Ethrel(2 halo-ethanephosphonic acid) in relation to the resistance of the suscept against the invasion of Phytophthora infestans. Peroxidase activities in potatoes treated with ethrel by means of polyacrylamide gel electrophoresis were also investigated.
1. The epinasty of leaf midrib was recognized after spraying the Ethrel on potatoes (Cultivar Norin No. 1). Lower leaves turned yellow 72 hrs. after spraying 100 ppm solution of the Ethrel.
2. Fifty ppm solution of the Ethrel inhibited the conidial germination of Phytophthora infestans. Abnormal germination of conidia of Phytophthora infestans was found in 25 ppm solution of the Ethrel.
3. Activities of all isozymes of peroxidase were significantly enhanced in the hypersensitive reaction(Interspecific hybrid 96-56-Race 0, Interspecific h brid SH-469-Race 0, Interspecific hybrid-1506(b)9-Race 0, Race 1, Race 4).
4. Activities of isoenzymes tended to degrade in the susceptible reaction(Interpecific hybrid-Race 4, Norin No. 1-Race 0, Race 1)at 6 or 10 hours after inoculation, but enhanced at 24 hours after an inoculation. In any case. all isozymes did not change qualitatively.
5. Activities of all isozymes enhanced in interspecific hybrids treated with Ethrel.
6. Activities of peroxidase enhanced 2 or 3 times in petioles and tubers of interspecific hybrids treated with Ethrel, as compared with the control. Hypersensitive reactions of Interspecific hybrid SH-469 to the infection of compatible Race 4 and Interpecific hybrid 96-56-Race 1 tended to be in tensitied by the Ethrel treatment.