Effects of Potato Tuber Age and Storage on Sesquiterpenoid Stress Metabolite Accumulation, Steroid Glycoalkaloid Accumulation, and Response to Abscisic and Arachidonic Acids

Publisher Website
Google Scholar
Abstract
Incompatible races of Phytophthora infestans elicited a hypersensitive response in potato slices from tubers stored at 4.degree. C. The response was characterized in part by the rapid accumulation of the fungitoxic sesquiterpenes, rishitin and lubimin. Compatible races grew and sporulated on slices from stored tubers and elicited little or no sesquiterpene accumulation. Potato slices from unstored tubers harvested in July, Aug. and Sept., however, accumulated low levels of rishitin and lubimin after inoculation with an incompatible race. Sesquiterpene accumulations in inoculated potato slices from tubers before cold storage were 10-20% of those from tubers after cold storage. Sesquiterpene accumulations were not different in slices from unstored tubers inoculated with a compatible or incompatible race, even though the disease reactions to these races were similar to those observed in slices from stored tubers. Storage at 4.degree. C generally increased the accumulation of sesquiterpenes in slices treated with crude elicitor preparations from the fungus. Abscisic acid (ABA), which inhibits rishitin and lubimin accumulation and enables incompatible races to grow and sporulate on slices from tubers stored at 4.degree. C, was ineffective in this regard in the unstored tubers. ABA increased sesquiterpene accumulations in the unstored tuber slices subsequently inoculated with an incompatible race and did not enable incompatible races to grow and sporulate. Storage of the tubers for at least 5 mo. was required for ABA to reduce sesquiterpene accumulations and to induce compatibility to an incompatible race in potato slices. The pattern of accumulation of steroid glycoalkaloids apparently did not change dramatically in slices from tubers before or after cold storage. The results raise questions about the role of sesquiterpenoid phytoalexins as the sole determinants of resistance in the reaction of potato tubers to infection with P. infestans.