Effects of soluble silicon on development powdery mildew(Sphaerotheca fuliginea) in cucumber plants

규소 시용에 의한 오이 흰가루병 발병억제

Effects of silicon application on development of colonies of Sphaerotheca fuliginea were examined. Cucumber plants were applied with nutrient solutions amended with different concentrations of soluble silicon and selected leaves were inoculated with known concentrations of conidia of the pathogen. Colony number per leaf, colony area per leaf, and germination rate of conidia of S. fuliginea collected from the inoculated leaves were reduced as silicate concentrations in the nutrient solutions increased from 0.05 to 4.10 mM. The increase in resistance of plants to mildew infection was apparently due to silicate accumulation in leaves, and there was no correlation between cation or ionic strength effects and the silicate treatments. Silicate treatment in growth medium remarkably suppressed powdery mildew development on cucumber. Colonies of mildew fungus were visible with over approx. 38.3% of the mature leaf surface, while that of the leaves in high Si plants was 2.3% observed at 51 days after transplanting. No significant differences were observed between 1.7 mM and 3.4mM silicate treatments. Conidial germination rates were significantly reduced by increasing Si amendments. Conidial germination ranged from 14.7 to 20.3% for plants grown in low Si solution(<1.40 mM), and from 9.0 to 12.4% for plants grown in high Si solution(>1.8 mM). Foliar applications of Si with ${\geq}$ 17.0 mM decreased the number of powdery mildew colonies. Persistence of Si foliar sprays effects on cucumber demonstrated that the 17 mM Si spray applied 4 days before inoculation with S. fuliginea reduced mildew colony formation. The relationship was positive and linear.

본 시험은 오이 양액재배시 배양액내 규산칼륨($K_{2}SiO_{3}$) 처리에 의한 흰가루병 방제여부를 검토하기 위하여 규산 칼륨($K_{2}SiO_{3}$, $25{\sim}27%$의 $SiO_{2}$ Kanto)을 0.85 mM(50 $mg{\cdot}L-^{-1}$), 1.7 mM(100 $mg{\cdot}L-^{-1}$) 및 3.4 mM(200 $mg{\cdot}L-^{-1}$)의 농도로 배양액에 처리하고 1.7 mM, 8.5 mM, 17 mM 및 34 mM의 농도로 엽면살포하였다. 생육중기(정식 51일)에 규산 3.4 mM 배양액 처리구는 흰가루병 병반면적율이 2.3%로 0.95 mM 처리구의 38.3%에 비해 현저히 억제되었다. 그러나 1.7 mM과 3.4 mM 처리간에는 현저한 차이가 없었다. 배양액내 규산의 농도를 0.05 mM에서 4.10 mM까지 증가시켰을 때 잎당 병반수, 병반면적 및 발아관 길이는 규산의 농도 증가에 따라 감소하였다. 규산을 처리한 잎에서의 분생포자 발아율은 처리농도가 높아질수록 현저하게 감소하였으며, 저농도 처리구(1.40 mM 이하)에서는 $14.7%{\sim}20.3%$, 고농도처리구(1.85 mM 이상)에서는 $9.0%{\sim}12.4%$였다. 2% 물한천 배지에서의 농도시험에서는 발아율이 $1.1%{\sim}2.0%$로 일정한 경향을 나타내지 않았다. 규산칼륨을 17 mM의 농도로 희석하여 엽면살포한 결과 무처리에 비하여 흰가루병 발생이 현저히 억제되었으며, 방제효과 지속기간은 병원균 접종후 4일까지였다.