SUMMARY: Ungerminated microconidia of Fusarium oxysporum have a mean cell DNA content of 0·134 × 10−12 g/cell with a guanine-plus-cytosine composition (% GC) of 50·75%. During germination, the first dry weight increase of the spore population was detected after 3 h incubation and the first germ tube appeared after 4 h. The total DNA of the culture sharply increased after 5 h, followed by a pause at 6 h. At this time the DNA content per nucleus was maximal and the first nuclear divisions were detected. Pauses in the rise of total DNA of the culture and in the [14C]adenine incorporation pattern suggest that there is partial synchrony in DNA synthesis at the beginning of incubation. This is also supported by the fact that until 8 h, only hyphae with 1, 2 and 4 nuclei were observed. [14C]adenine incorporation into DNA averaged 2·68% of the total taken up in 10 h incubation.
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