The effect of storage temperature, time and spore source on the germination of Cronartium flaccidum and Peridermium pini aeciospores in vitro

Authors: Kaitera, Juha
Journal: Karstenia, Volume 39 (1999), Issue 2, pages 69-75.
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Key words: Cronartium flaccidum, germination, Peridermium pini, pine stem rust, Pinus sylvestris, storage, temperature

Abstract:  The effect of temperature and time of storage on the germination of aeciospores of Cronartium flaccidum (one source) and Peridermium pini (5 sources) were studied on malt agar with added pine needle extracts, and water agar. The storage temperatures ranged from -160 °C to +25 °C, and the time of storage from 7 days to 2 years. The rate of aeciospore germination remained higher after storage at low temperatures than at high temperatures, as spores stored at high temperatures lost their viability within a few months after storage. The two-year period of storage, however, reduced the germinability of the aeciospores significantly even at low temperatures. Aeciospores of C. flaccidum lost their viability more rapidly than those of P. pini.
Storage strongly reduced the subsequent ability of germ tubes to form vesicles. No vesicles were formed on a water agar substrate after 3-6 month-storage at +4 – +25 °C. At lower temperatures, the ability to form vesicles decreased more slowly, but vesicles were formed in individual spore samples as abundantly as at the beginning of the experiment when these were stored at between -22 °C or -70 °C for 2 years. The results suggest that aeciospores should be stored at low temperatures when needed for future inoculations in order to retain the highest possible viability.