Abstract
Length of time from inoculation to hypersensitive death of infected potato cells can be taken as an indication of the degree of hypersensitive reactivity. The earlier the hypersensitive cell death after inoculation, the higher the hypersensitive reactivity. In this study, observation was made of the time until hypersensitive cell death of potato tuder tissues, which had been inoculated with an incompatible race of Phytophthora infestans at intervals after cutting. The results showed that fresh disks having low or no reactivity attained about half of the maximum hypersensitive reactivity at 8-9hr and the maximum reactivity at about 16-20hr, after cutting. In a second experiment, the disks were treated with 5ppm of blasticidin S (BcS), an inhibitor of protein synthesis, for 15min at various times after cutting, and then all the treated ones were inoculated at the same time after cutting, namely, at 16.5hr. The microscopic observations showed that, the longer the time from cutting to BcS treatment, the earlier the hypersensitive death of the infected cells. It was also observed that the time until cell death reached the maximum when the disks were treated with BcS at 16hr after cutting. Findings indicated that the treatment with BcS can fix and maintain the hypersensitive reactivity to almost the level the cells have attained up to the treatment. The analysis using BcS treatment disclosed that there was a lag of about 4hr before the reactivity began to develop.
