キク褐斑病菌,Septoria obesaの分生胞子の発芽に影響を及ぼす要因

Inoculum concentration, age of cultures from which conidia were taken and light conditions were examined as factors affecting condium germination of S. obesa. Conidia for inoculation were taken from cultures which were started by streaking the conidia to vegetable juice agar plates and incubated under continuous light. When the concentration of the inoculum was 10^6 conidia/ml (= 3500 conidia/ <cm>^^^2 agar plate), germination of conidia was suppressed strongly even the conidia were taken from young cultures. At a lower concentration of <10>^^^5 conidia/ml (= 350 conidia/<cm>^^^2 agar plate), conidia germinated well. Germination of conidia which were taken from cultures with one-week incubation under continuous irradiation of near ultraviolet radiation (NUV) was not suppressed by light during germination. However, conidia which were taken from cultures with 4-week incubation under continuous NUV irradiation were completely inhibited to germinate by light. Effective wavelengths for suppression of conidium germination were NUV region shorter than 357 nm. Near ultraviolet radiation also suppressed the growth of germ tubes. From these observations it will be concluded that viability of conidia of S. obesa decreased by continuous irradiation of NUV and germination of conidia is suppressed by the same wavelengths of radiation.