• 作者： 劉顯達
• 作者服務機構： 臺灣省立屏東農業專科學校
• 中文摘要： 病原菌分泌的體外酵素，為其引起疾病的致病物質之一。果膠物質為植物細胞之主成分，在病變過程中，病原菌分泌的果膠分解酵素可能佔重要地位。 由水稻紋枯病病組織分離出八個病原性強弱不同的菌株，在28℃培養於含2％（W/V）Pectin的Bateman氏培養基中經七天之培養，瀘液中發現Pectin trans-eliminase（PTE）活性和菌株之病原性成正相關（複相關係數r＝0.94）。紋枯病菌分別培養於以Carboxymethylcellulose（CMC）代替Batemans培養基中之Pectin為含2％（W/V）CMC的培養基，和豆瓣培養基中，測其培養濾液中纖維分解酵素及磷脂分解酵素，結果酵素活性與其菌株之病原性似為無關。 水稻植株（臺中65號）經接種紋枯病菌二天後，PTE活性隨病勢發展而增加，至第四天高達45個酵素活性單位，以後PTE活性逐漸下降。 PTE經硫酸銨鹽析及柱層分析純化後，其活性較原來培養濾液中PTE活性增加十五倍。且此等純化之PTE不合有纖維分解酵素及磷脂分解酵素。以經硫酸銨鹽析部份純化的PTE處理水稻葉片能引起黃化，褐化之病徵。 PTE作用之最適pH值為5.5。Ca （1 u mole ml）具促進PTE活性，但Mg ，K 則無此作用。PTE於100℃處理二十分鐘，失去69％活性。 由紋枯病菌菌株之病原性與PTE活性成正相關，在病變初期PTE活性增高等現象，推論PTE在紋枯病病變過程佔重要地位。
• 英文摘要： Sheath blight is one of the mostdestructive diseases of the rice plantin Taiwan. The disease is caused byThanatephorus cucumeris f. sp. sasakii. Eight isolates of this pathogen,namely K-1, K-2, K-3, A-1, A-4, 4-1,80-2, and 72-1, with different patho-genicity were chosen to study the rela-tionship between their pathogenicityand their ability of producing variousenzymes. Bateman's medium containingMgSO 0.5g, KH PO 1.0 g, CaCl 0.9g,FeCl 0.01 g, Na-asparagine 1.17 g,thiamine 50 ug, A-Z solution 1 ml andpectin 20 g per liter was used as abasic medium for the assay of pecto-lytic enzymes. When assay for cellulaseactivity, carboxymethyl cellulose(CMC) was used in the place of pectin.A bean cotyledon medium was chosenfor the purpose of producing phospha-tidases. Filtrates from 7-day-old culturesof both virulent and avirulent isolatesshowed that the pathogenicity of theseisolates was closely correlated withthe production of pectin trans-elimin-ase (PTE), but not cellulase or phos-phatidases. PTE activity was detectedby measurement of absorbance at 550nm of thiobarbituric acid reacted withthe unsaturated product formed in thepectin solution. Pectin trans-eliminase was detectedin T. cucumeris-infected rice tissues dur-ing the early phase of the disease de-velopment, its activity increased asdisease progressed, but declined in thelater phase of pathogenesis. Pectin trans-eliminase was purified15-fold from crude culture filtrate byprotein fractionation with ammoniumsulfate at 80-100% stauration and foll-owed by column chromatography withSephadex G-100. The purified enzymewas free of cellulase and phosphati-dases. The optimum pH for PTE is at 5.5.Ca (1 u mole/ml) but not Mg orK has a stimulating effect on PTEactivity. When detached leaves of rice weretreated with partially purified PTE,yellowing and browning discolorationsappeared on the leaves as symptoms. The parallelism found between thepathogenicity and the pectin trans eli-minase producing ability of these fun-gal isolates, as well as the coincidenceof the highest PTE activity at the earlystage of the disease development str-ongly suggest that PTE produced byT. cucumeris f. sp. sasakii might have animportant role in the pathogenesis ofrice sheath blight disease.
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