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Physiology and Biochemistry

Optimal Conditions for In Vitro Growth, Asexual Spore Release, and Germination of Thyronectria austro-americana. W. R. Jacobi, Assistant professor, Department of Botany and Plant Pathology, Colorado State University, Fort Collins 80523; Phytopathology 74:566-569. Accepted for publication 31 January 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-566.

Growth of the honeylocust pathogen Thyronectria austro-americana on solid and liquid media was assessed at various temperatures, on carbon and nitrogen sources, and on other nutrients. Spore release from excised naturally formed pycnidia was practically instantaneous when water was added at temperatures between - 15 and 40 C after storage at 25 C and 35- 45% RH for 12 mo. Spore germination occurred from 15 to 40 C with optimal germination at 25- 35 C. Germination was delayed at 96- 75% RH over that found at 100% RH and completely inhibited at 62%. Carbon and organic nitrogen compounds promoted, but were not necessary for, germination. Water extracts of honeylocust wood stimulated germination. The fungus appears to be very well adapted for growth and dissemination in the varied climates where the host is planted.