• Korean Journal of Medicinal Crop Science
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• v.10 no.3
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• pp.155-161
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• 2002

Using semi-selective (SS-) and selective (Jee-) medium, we identified the pathogens isolated from the symptomatic plants and soils collected from different locations, such as Suwon, Andong, and Youngju, as P. drechsleri, which is Phytophthora root rot causal agent of A. macrocephala. At $25^{\circ}C$, these isolates were grown faster on 10% V8A (V8 juice agar) medium than on PDA (potato dextrose agar) with hyphal swelling, but no growing was observed at below $5^{\circ}C$ and over $40^{\circ}C$. In order to identify the pathogenicity of each isolate, seedlings of A. macrocephala were inoculated with mycelium -zoospore suspended inoculum, which was prepared by culturing on 10% V8A medium and homogenizing in distilled water. By this method, wide ranges of pathogenicity were observed as follows; $5.0%{\sim}26.4%$ of disease severities concerning the lesion areas of the top plants and $23.5%{\sim}72.2%$ of disease incidences. Therefore, this was considered as a efficient method to identify the pathogenicity of P. drechsleri in large scale screening. P-A200073, isolated from soils in Andong, and P-9755, from the root of symptomatic plant of A. macrocephala in Suwon, showed the highest degree of pathogenicity to the seedlings. By these isolates, lesion areas and disease incidences of the inoculated seedlings were occurred $26.4%{\sim}63.2%$ and $25.1%{\sim}72.2%$, respectively. However, no symptoms were observed in uninoculated control. Same pathogens were reisolated from roots and lower stems of the inoculated plants, but not from leaves.

• Korean Journal of Medicinal Crop Science
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• v.9 no.3
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• pp.211-219
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• 2001

The disease incidence rates of Phytophthora root rot of A. macrocephala caused by P. drechsleri were dramatically increased in two distinctive periods at experimental fields of National Crop Experiment Station(NCES), Suwon, in 1999 and in 2000 ; one was in the period of 30 to 45 days old seedling stage in spring and the other was just after heavy rainy season in late summer or in early fall. The disease was occurred at seedling stage under the conditions of ${{\geq}15^{\circ}C}$ of average temperature with ${{\geq}100mm}$ rainfalls for 20 days and the tendencies were similar in both year. By the disease, rhizome propagated field was more damaged(18.6%) than seed propagated field(56.0%). Comparing the disease incidence rates at five different fields in Suwon, Youngju and Andong, the damages at soil improving fields and non-mulching fields were less severe than those at continuous cropping fields without soil improvement and mulching fields and occurrence. Expansion of the disease were seemed to be highly related with the populations of P. drechsleri in soils depend on the cultivation method and field conditions. Although the populations of the pathogen in soils collected from Andong and Youngju, in which rhizome were continuously propagated for two and three years respectively, were comparably less than that from Suwon, in which rhizome were propagated for one year, however, the damages by the disease were more severe in Andong and Youngju. So, two or more years of cultivation at the same field may not be useful for Atractylodes plants..