- 學位論文
木黴菌降解草酸能力與抑制白絹病菌之間的相關性研究
Study on Correlation between The Capacity of Oxalic Acid Degradation of Trichoderma spp. and Their Growth Inhibition of Sclerotium rolfsii
摘要
引起作物白絹病的Sclerotium rolfsii Sacc.，其寄主範圍非常廣泛，約可為害100科500種以上的農作物。白絹病菌在感染作物時會分泌草酸降低植物表面的pH導致植物鬆軟潰爛。本研究主要在探討Trichoderma分解草酸能力與其抑制S. rolfsii生長之間的相關性。利用無添加草酸的modified potato dextrose broth (mPDB)培養不同寄主來源的S. rolfsii，Sr170 (來至文心蘭)、Sr P-1 (來至花生)、Sr 140 (來至毛豆)、Sr200 (來至姜黃)，在25℃、100rpm下培養，經3、5、7、11、14天之培養濾液，分別用過錳酸鉀滴定檢測S. rolfsii草酸分泌的濃度，結果顯示不論寄主是否同科，S. rolfsii草酸分泌的濃度都不同，草酸濃度範圍在9.88~29.5mM。利用添加草酸的mPDB培養T2 (Trichoderma harzianum)、T3 (T. virens)、ETS332 (T. harzianum)、KS-CO R6-1 (T. harzianum)測試分解草酸的能力，加入草酸最終濃度分別為20mM、35mM、50mM，在25℃、100rpm下培養5天，結果顯示在固定草酸濃度為20mM時T2及ETS332能最快分解全部的草酸，只需要3天。當培養時間固定為5天時ETS332比其他木黴菌株更能分解35mM、50mM的草酸，分解率分別為9.46％、6.13.％。利用添加草酸的modified potato dextrose agar (mPDA)進行4株Trichoderma與不同寄主來源的S. rolfsii作對峙培養，加入草酸最終濃度為20mM，結果顯示4株Trichoderma菌落都能生長覆蓋到S. rolfsii，但隨著草酸濃度上升，Trichoderma的生長速率會下降，因此若使用citric buffer將pH維持在5.4時，會提高了Trichoderma在有添加草酸的mPDA上的生長速率。用花生進行溫室試驗發現S. rolfsii的致病性與草酸生成量並無正相關性，反而是草酸生成力最弱的Sr170有最高的致病性。根據不同處理方式觀察到的結果顯示，測試的Trichoderma能有效的抑制草酸生成力低的Sr170，其中最有效的方式是在花生播種時接種Trichoderma及同時接種Trichoderma和S. rolfsii，表示欲利用Trichoderma有效防治白絹病的前提是，在土壤中需先定殖一定量的Trichoderma；同時也證明抑制S. rolfsii生成草酸確實可以防治病害的發生。
並列摘要
Southern blight caused by the soilborne fungus Sclerotium rolfsii Sacc. Was one of the most destructive diseases in the world. The host range of this pathogen was at least 500 species in 100 families. Oxalic acid secreted by S. rolfsii reduced the pH of infected plant’s surface, and finally infected plant became fester and die quickly. In this study, the correlation between antifungal capability of Trichoderma spp. and its degradation of oxalic acid from S. rolfsii was tested. Four strains S. rolfsii which were isolated from different hosts, Oncidium, peanuts, soybeans, turmeric, respectively, were used in this research. They were cultured on modified potato dextrose broth (mPDB) without of oxalic acid at 25oC, 100rpm rotation and then using the potassium permanganate titration to detect the oxalic acid secretion from S. rolfsii at the 3rd, 5th, 7 th, 11 th,14 th day of incubation. The results showed that concentration of oxalic acid secretion were different with different strains of S. rolfsii, in the range of 9.88 ~ 29.5mM. The oxalic acid degradation of Trichoderma spp. were studied using four strains, T2 (Trichoderma harzianum), T3 (T. virens), ETS332 (T. harzianum) and KS-CO R6-1 incubated on the mPDB added oxalic acid. These four strains were incubated five days at 25oC, 100rpm. With the same concentration of oxalic acid, 20mM, T. harzianum strain T2 and ETS332 showed the fastest degraded capability after three days incubation. Both strains could degrade all oxalic acid presented in the medium. When using the different concentration of oxalic acid, 35mM and 50mM, among all of studied strains, T. harzianum strain ETS332 also showed the highest ability to degrade oxalic acid, 9.46%, 6.13%, respectively, after 5 days incubation. Four strains of Trichoderma spp. and four strains of S. rolfsii were co-cultured on the in the modified potato dextrose agar (mPDA) added different concentration's oxalic acid. The result showed that all of four strains of Trichoderma spp. could grow cover the mycelium of S. rolfsii but with the higher oxalic acid concentration, the growth rate of Trichoderma spp. became slower. The pH of medium was maintained at 5.4 by using citric acid buffer could improve the tolerance of Trichoderma spp. to oxalic acid. For greenhouse experiment carried on peanut, the results indicated that pathogenic capacity and production of oxalic acid of S. rolfsii were not positive associated. The weakest producer of oxalic acid , Sr170, had the highest pathogenicity to peanut among 4 strains. Under different treatment with Trichoderma strains, the most effective method to reduce the disease severity of Sr170 was inoculation of Trichoderma at sowing stage or inoculation of Trichoderma and S. rolfsii at the same time. The result showed that to take effective disease control of S. rolfsii treated by Trichoderma spp., it was necessary to provide a certain amount of Trichoderma in the soil first. It also demonstrated that the inhibition of OA secretion from S. rolfsii could prevent the occurrence of southern blight disease of agricultural crops.
參考文獻
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延伸閱讀
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