Abstract
By inoculating cut surface of potato-tubers with an incompatible race of Phytophthora infestans, relations between the degree of resistance and time course of rishitin accumulation were studied. In highly resistant tissues, rishitin became detectable earlier after inoculation than in tissues with medium and low levels of resistance, and also the increase in rishitin content was more rapid and reached maximum earlier as the disease development stopped. As a result, the maximum rishitin content was relatively low in the case of highly resistant tissue, as compared with the one with medium resistance. With medium resistance, rishitin began to be chemically detectable later, but the increase was as rapid as with the highly resistant tissue. In this case the rishitin content reached the highest amount as compared with tissues with both high and low resistance. With the tissue with a low level of resistance, on the contrary, the time of onset of rishitin accumulation was late and the increase in rishitin content was slow. These phenomena suggest that rishitin plays an important role in the resistance of potato to late blight.
