Resistance of storage roots of 46 sweetpotato cultivars to foot rot disease caused by

Despite the development of several cultural pest controls, foot rot disease has severely damaged sweetpotato crops in southern Japan since 2018. A more effective solution would be to breed resistant cultivars. To promote the breeding of cultivars whose stems are resistant to this disease, we previously developed a laboratory resistance test using sweetpotato stems. The laboratory test can indirectly evaluate the foot rot resistance of stems in the field test, which is usually used to evaluate cultivar resistance in breeding programs. In the present study, we improved laboratory test by using sweetpotato storage roots and investigated the resistance of storage roots of 46 cultivars. We analyzed the correlations of various indices of resistance of storage roots between the laboratory test and the field test, and found that the index of the laboratory storage root test correlated significantly with the proportion of severely rotted storage roots in the field test in some cases. This result indicated that the laboratory storage roots test could indirectly evaluate the foot rot resistance of storage roots in the field test. These two laboratory tests using stems and storage roots could help breed cultivars whose stems and storage roots are resistant to foot rot.