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Physiology and Biochemistry

Terpenoid Accumulation and Browning in Potato Sprouts Inoculated with Phytophthora infestans. N. Lisker, Department of Plant Pathology, University of Kentucky, Lexington, KY 40506; J. Ku(, Department of Plant Pathology, University of Kentucky, Lexington, KY 40506. Phytopathology 68:1284-1287. Accepted for publication 11 April 1978. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1284.

Zoospores of races 4 and 1,2,3,4 of Phytophthora infestans elicited browning and the accumulation of the terpenoids rishitin, lubimin, phytuberin and phytuberol in sprouts of Kennebec (R₁) Russet Burbank (r) and Red Pontiac (r) potatoes. There was little or no difference in the quantities of the terpenoids which accumulated in sprouts from potatoes inoculated with a compatible or incompatible race of P. infestans. Autoclaved, cell-free sonicates of P. infestans, Pythium aphanidermatum, Achlya flagellata, Phytophthora parasitica, and Aphanomyces euteiches also elicited browning and the accumulation of terpenoids. As with zoo spores, there was little or no difference in the extent of browning or quantities of terpenoids that accumulated in sprouts from tubers of a cultivar which lacked R genes for resistance and those from a cultivar with R₁. Kennebec potato sprouts treated with sonicates of P. infestans browned more intensely and accumulated more of the terpenoids at 19 C than at 14 or 25 C, but neither browning nor terpenoid accumulation were detected at 30 C and 36 C. Sprouts inoculated with zoospores of P. infestans browned first closest to the growing point and then over the length of the inoculated area. There was no difference in the appearance of browning on sprouts treated with cell-free sonicates of the fungi. Growth and sporulation of P. infestans were not apparent on inoculated sprouts. The steriod glycoalkaloid content in sprout sections 5 cm from the growing tip was threefold that in the 5 cm at the base.