Responses of potato tuber to infection by Fusarium sambucinum

Fusarium sambucinum causes dry rot in tubers of Solanum tuberosum. Since relatively little is known about the nature of dry rot disease development, infection off. sambucinum on tissue discs prepared from tubers of potato varieties that are susceptible or moderately resistant to this disease was studied. Increases in lignin content, and polyphenol oxidase and peroxidase activities were detected after infection. Peroxidase increased most strongly in tuber tissue that was just ahead of the advancing hyphae. Constitutive polyphenol oxidase activity was highest in the more resistant as compared to susceptible varieties. Polyphenol oxidase and peroxidase activities as well as content of chorogenic acid and the sesquiterpenes rishitin, lubimin, phytuberin and phytuberol increased as a result of infection. These increases correlated with the amount of tissue infected rather than the resistance of the tuber tissue to infection. (C) 1998 Academic Press.