| 英文摘要 |
"In Han Country Samsung Township, Nantou Country Tsaotun Township, Changhua Country Fangyuan Township and sihufa Town, there are a lot of Allium fistulosum dieing continually in these cultivate area. This is more serious in May and August and the winter with more rain. Phytophthora parasitica Dastur was isolated and inoculations were made with Zoospore suspension and mycelium block on Dahan, Small Han, Black leaf, hyphal of North onions root, and stem individually, it will be sick on the eighth day. The P. parasitica from the diseased plant can grow at 24-28°C, the colony culture in V-8 agar medium does not have special patterns, with aerial hyphae; the colony culture in PDA medium has rose petal-like pattern, there are 1-3 pyriform sporangia on the top of each sporangiphore, with papilate and non-deciduous. The sporangia release zoospore then it will inter- or nested proliferate, the sporangia size is 26.7-43.4×23.4-33.4μm, the mean is 27.6×34.6μm. The sporangia length/width (LIB) is 1.25μm, the papilate size is 3.3-10×3.3-10μm, the mean is 6.5×6.6μm, the papilate length/width (LIB) is 0.98μm. Chlamydospores and coralloid hyphal swellings, the chlamydospores size is 10.0-26.7μm, the mean is 18.6μm. The greenhouse inoculation prove P. parasitica with pathogenic to green onions variety, but different variety with different disease degree. The field survey of Small Han ＂' Black leaf diseases rate, after growing for 1 week are 8.1% and 2.5%, but in the 3 weeks the diseases rate are 67.8% and 8.1%. It means Black leafs resistance is stronger; it is be able to plant in the epidemic disease areas. Small Han is very susceptible, it only be able to plant in the unepidemic disease areas." |
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