Abstract
인삼 재배지에서 가장 큰 피해를 나타내고 있는 뿌리썩음병원균은 Cylindrocarpon destructans로 연작장해의 원인으로 작용하고 있다. 2011과 2012년에 걸쳐 인삼 뿌리썩음병 발병포장으로부터 뿌리를 수집하여 병징 구분 후 57종의 C. destructans를 분리하였다. 분리한 뿌리썩음병원균중에서 34균주(61%)는 병원성이 낮았으며, 21균주(37%)는 무상처 접종에서도 병반을 형성하여 강한 병원성을 나타내었다. 또한 이들 분리균들을 PDA 배지에서 15일 배양한 결과 최적의 생장온도는 <TEX>$20^{\circ}C$</TEX>였으며, <TEX>$35^{\circ}C$</TEX>에서는 병원성에 관계없이 모두 생장하지 못하였다. 병원성에 따라 균총의 색과 균사의 생장정도에 차이를 나타내었다. 강한 병원성 균주는짙은 갈색을 나타낸 반면 병원성이 약한 균주들은 베이지색 또는 옅은 갈색을 나타내었다. pH 변화에 따른 균사 생장에 미치는 효과 조사를 위해 수경 재배한 결과 pH 7.0에서 보다 pH 5.0에서 균사생장이 양호하였다. 뿌리에서의 상처는 pH 변화와 관계없이 발병도를 더욱 증가시켰다. 인위적으로 조성한 발병 토양에 1-4년생 인삼뿌리를 이식하여 재배한 결과 2년생 뿌리에서 가장 감수성이었으며, 발병률도 79.5%로 가장 높았다. 뿌리썩음병 발병정도는 토양 내 접종 병원균의 밀도에 따라 영향을 받는 것으로 나타났으며, 병원균 접종농도 <TEX>$3.5{\times}10^2cfu/g$</TEX> 처리구 보다 <TEX>$2.0{\times}10^3cfu/g$</TEX> 처리구에서 높았다. The fungus Cylindrocarpon destructans is the cause of root rot in many ginseng production areas in Korea. A total of 57 isolates of C. destructans were recovered from diseased roots in a survey of ginseng-growing fields from 2011-2012. Among these isolates, 37% were classified as highly virulent (causing lesions on unwounded mature roots) and 61% were weakly virulent(causing lesions only on previously wounded roots). Radial growth of highly and weakly virulent isolates on potato dextrose agar was highest at <TEX>$20^{\circ}C$</TEX> and there was no growth at <TEX>$35^{\circ}C$</TEX>. Mycelial mass production was significantly (P = 0.05) lower at pH 7.0 compared with pH 5.0. To study the effects of pH (5.0 and 7.0) and wounding on disease development, ginseng roots were grown hydroponically in nutrient solution. Lesions were significantly larger (P < 0.01) at pH 5.0 compared with pH 7.0 and wounding enhanced disease by a highly virulent isolate at both pHs. In artificially infested soil, 2-yearold ginseng roots were most susceptible to Cylindrocarpon root rot among all root ages tested (1 to 4 years) when evaluated using a combined scale of disease incidence and severity. Root rot severity was significantly (P<0.05) enhanced by increasing the inoculum density from <TEX>$3.5{\times}10^2cfu/g$</TEX> of soil to <TEX>$2.0{\times}10^3cfu/g$</TEX> of soil.
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