| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1993: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1992: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
Ectoparasitic powdery mildew fungi produce all vegetative and reproductive organs except haustoria on the surface of their host plants. In the literatures there are contradictory evidences concerning the effects of water on growth of powdery mildew fungi. For example, some researchers reported harmful effects of water on these fungi, such as bursting of conidia or damage of secondary hyphae. In contrast, some researchers successfully inoculated grasses with powdery mildew conidial suspensions in water. However, all of the latter researchers adopted water just for medium ingredient for spore suspension, and thus it is plausible that the water disappears soon by evaporating from the surface of leaves after inoculation before the water gives harmful effects, if any. Thus, no report is available concerning the effects of water on the differentiation process from spore germination to sporulation of powdery mildew fungi. In this stude, it is shown that water has no effect on the viability of Erysiphe graminis if ther are incubated in water without being fried, and the fungus eventually formed conidia 120 h after the onset of incubation. Moreover, it is reported that the viability of E.pisi is also unaffected by immersing in water after inoculation to barley coleoptile. However, immersed E.pisi formed abnormally elongated germ tubes at higher frequency that of unimmersed ones. This phenomenon was explained as follows ; the emerging sites of germ tubes were affected by environment conditions to which conidia had been exposed ; if the conidia were incubated in air, more than 60% of germ tubes emerged from lower sites of conidium equater, while the emerging sites of germ tubes were at random when the conidia had been incubatedin water. Moreover, short germ tubes of E.graminis were formed at high frequency and they tried to penetrate barley coleoptile cells in air condition, while their formation frequency in water condition was much lower, and even if they were formed, their
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