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Effect of Clove and Its Major Component on Control of Rhizoctonia Damping-off of Cabbage Seedlings
|關鍵字:||Cabbage;甘藍;Rhizoctonia damping-off;Botanical pesticide;Clove;Cinnamon;Eugenol;Culture medium;甘藍立枯病;中藥;植物保護劑;丁香;肉桂;丁香酚;栽培介質||出版社:||植物病理學系||摘要:||
甘藍立枯病菌( Rhizoctonia solani AG-4 )引起甘藍幼苗猝倒與死亡的現象，是甘藍幼苗栽培的主要限制因子之一。在培養基平板上篩選109種中藥對R. solani AG-4的抑制效果，發現丁香及肉桂具有完全抑制 R. solani AG-4菌絲生長的功效；高溫高壓滅菌過之丁香與肉桂亦具有抑制 R. solani AG-4菌絲生長的效果，顯示兩中藥的抑菌有效成分均具有熱穩定性。將丁香或肉桂添加於帶菌的介質中，結果僅有丁香可顯著地( p < 0.05 )降低甘藍幼苗之罹病率；至於肉桂則不具有防治甘藍立枯病發生的功效。在溫室進行大規模的防治試驗，顯示介質中添加0.5%( w/v )丁香可有效降低甘藍立枯病的發病率達52~60%。此外發現丁香油亦可有效防治甘藍立枯病。將丁香粉末利用不同溶劑萃取，並進行抑菌的生物分析，結果証明由正己烷萃取之萃出物可完全抑制R. solani AG-4菌絲生長。進一步，以管柱層析法純化正己烷萃取物並做活性測試，結果發現管柱層析純化之主要成分的2500倍稀釋液可完全抑制 R. solani AG-4菌絲的生長。此主要成分經核磁共振光譜儀NMR 300MHZ 分析，確定為丁香酚( eugenol )，其化學組成與結構分別為C10H12O2與 。此外丁香的抑菌物質具有揮發的燻蒸特性，在光學顯微鏡及掃描式電子顯微鏡下觀察，發現丁香燻蒸處理過之菌絲表面出現皺縮，細胞壁穿孔、原生質滲漏，菌絲或菌絲尖端腫脹破裂及菌絲分枝出現異常等現象，利用薄層色層分析檢測，發現丁香抑菌與殺菌的揮發性物質亦為丁香酚。綜合上述諸研究証明丁香添加於介質中防治甘藍立枯病的主要成分為丁香酚。
Damping-off disease caused by Rhizoctonia solani is a serious disease of cabbage, especially in seedlings grown in culture medium. In 2% ( w/v ) water agar plates 109 Chinese medicines were evaluated for their effect on mycelial growth of the pathogen. Among those, clove ( Eugenia caryophyllata Thunb. ) and cinnamon ( Cinnamomum cassia Blume ) inhibited completely the mycelial growth at the rate of 0.5% ( w/v ) whether they were autoclaved or not. Amendment of BVB No.4 peat moss medium infested by the pathogen with clove was significantly effective in reducing the disease incidence of damping-off. However cinnamon amendment wasn't effective in the disease control. Clove was added at each rate of 0, 0.25, 0.5, 0.75, and 1% ( w/v ) respectively to artificial infested medium. It at the rate of 0.5% ( w/v ) showed markedly reduction in the disease incidence of damping-off by 52~60% compared to non-treatment as a control. The similar results were also confirmed in three-time large-scale experiments in the greenhouse. The essential oil of clove emulsified by mechanical method was applied to control the damping-off of cabbage. The disease incidence was significantly reduced more than 50% by a 500-fold dilution of the emulsified clove oil compared to non-treatment as a control. The powders of clove flower buds were extracted with methanol for three times. The combination of extractives was partitioned with n-hexane and ethyl acetate. Finally, the rest was extracted with water. The extractives from different solvents were tested for their bioactivity on mycelial growth of the pathogen. The n-hexane extractives showed significant effect on suppression of mycelial growth at 2000-fold dilution. In advance, the n-hexane-soluble extractive was subjected to systemic separation and purification by column chromatography and thin layer chromatography. One major compound and two minor compounds were obtained and used to test their bioactivity. The mycelial growth of the pathogen was completely inhibited by 2500-fold dilution of the major compound of n-hexane-soluble extractive. This compound was characterized by 1H NMR spectrum as eugenol. In the study, the fumigation effect of clove powder solution on mycelial growth of the pathogen was observed and proved. The inhibition of mycelial growth by clove-fumigant was increased with increasing the concentrations of clove in water solution. Observations under light microscope and scanning electron microscope indicated that the hyphae or hyphal tips swelled, plasma seeped around the hyphae, plasma leaked out, cell wall distorted, branched abnormal or fused with main hypha, hyphal tips warped or looped, and surface of hyphae wrinkled were caused by clove-fumigant treatment for 24hr. The clove-fumigant was identified as eugenol by bioassay method and thin layer chromatography. The results suggest the major component inhibiting damping-off of cabbage seedlings with clove is eugenol.
|Appears in Collections:||植物病理學系|
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