VIEW ARTICLE

Physiology and Biochemistry

Effect of Abscisic Acid on Rishitin and Lubimin Accumulation and Resistance to Phytophthora infestans and Cladosporium cucumerinum in Potato Tuber Tissue Slices. J. W. D. M. Henfling, Department of Plant Pathology, University of Kentucky, Lexington 40546, Present address of senior author: The International Potato Center, Apartado Postal 5969, Lima, Peru; R. Bostock(2), and J. Kuc(3). (2)(3)Department of Plant Pathology, University of Kentucky, Lexington 40546. Phytopathology 70:1074-1078. Accepted for publication 14 May 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-1074.

A number of terpenes similar to the potato sesquiterpenoid stress metabolites (SSM) were tested for their effect on the accumulation of rishitin and lubimin in potato tuber slices treated with an elicitor preparation from cultures of Phytophthora infestans. Abscisic acid (ABA) was found to be the only compound that consistently and strongly inhibited rishitin and lubimin accumulation. ABA also markedly inhibited the accumulation of rishitin and lubimin in slices inoculated with incompatible races of P. infestans. Incompatible races grew and sporulated on slices treated with ABA prior to inoculation, and the reaction was indistinguishable from that induced by compatible races. ABA did not affect the accumulation of rishitin and lubimin or fungal growth in slices inoculated with compatible races of the fungus, and it did not stimulate fungal growth in defined media. Cladosporium cucumerinum, a pathogen of cucumber but not of potato, grew well and sporulated abundantly on tuber slices treated with ABA prior to inoculation. ABA, however, increased the accumulation of rishitin and lubimin in slices inoculated with C. cucumerinum. The reduced accumulation of rishitin and lubimin in potato slices treated with ABA did not appear to be responsible for the conversion of incompatible to compatible interactions with P. infestans. The data cast some doubt on the role of the SSM as primary agents responsible for containing the fungus in incompatible interactions of potato and P. infestans.