The amino acid content of potato plant varieties and their resistance to attack by Phytophthora species

Abstract

AbstractNutritional experiments were carried out to determine the suitability of 22 amino acids as sole sources of nitrogen for the culture of Phytophthora infestans and Phytophthora erythroseptica. The results showed that whilst P. erythroseptica was able to utilise all amino acids supplied reasonably well with the exception of DL lysine, P. infestans was more exacting in its requirements producing reasonable growth on less than half the number supplied. Examination of the free amino acid pool in the tissues of 14 varieties of potato tuber and 8 varieties of leaf showed that approximately 15 readily utilisable amino acids were present as the basic complement in the tuber tissues; the leaf tissues contained a smaller number of amino acids. Additions of water‐soluble tuber extracts to a nitrogen‐limited medium improved the growth of both fungi but the growth response of P. infestans was more varied than that of P. erythroseptica. There was no apparent correlation between the amino acid content of the potato tissues and the amino acid requirements of the parasite in relation to differential varietal resistance.