Effects of Temperature on the Conidium Germination and Appressorium Formation of Botrytis cinerea Pers.

Abstract

Effects of temperature upon the conidium germination and appressorium formation of Botrytis cinerea Pers. were investigated on glass slides.
1) Conidia of this fungus were able to germinate in the range of 5-32°C. At 10°C, however, germination was so much delayed that only 60 per cent of conidia germinated within 48 hours.
2) The optimum temperature for the conidium germination was between 20 and 30°C, and the maximum temperature was 35°C. The minimum temperature seemed to be lower than 5°C.
3) Appressorium formation occurred between 10 and 30°C, the optimum temperature being in the range of 15-20°C. Appressoria were formed fairly well even at 10°C, despite the delay of conidium germination. At 25°C or above, both the germination and germ tube elongation were favored, but appressorium formation was poorly detected.At 30°C the germ tube elongation was markedly accelerated, but no formation of appressoria was recognized.
4) Young conidia, 2 days after their formation, commenced to germinate after 2 hours at 20°C on glass slides. Most of the conidia formed an appressorium at the tip of the germ tube after 4-6 hours of incubation. After 8-12 hours of incubation, most of the appressoria thus formed germinated again with elongating hyphae which branch ed during further incubation.
5) At 15°C, conidia germinated well, but elongation of hyphae and appressorium formation were not conspicuous within 24 hours. Appressoria were formed after 48 hours. At 20°C, conidia germinated well and the elongation of germ tubes was vigorous accompanying marked formation of appressoria. At 25°C, two germ tubes sometimes protruded from a single conidium. In this case, appressorium was usually formed only on one of the germ tubes, while the other elongated as a vegetative hypha. The germ tube elongation was most prominent at 25°C. At 30°C, conidia germinated usually without forming appressoria.