篩選能產生次級代謝物以誘導植物抗病毒病害的土壤微生物

Abstract

近年來，社會意識逐漸開始關心化學農藥的使用對於環境與非病原生物所產生的負面影響，因而促進其他植物病害防治替代方法的發展。土壤微生物能夠產生許多具有廣泛生物活性的次級代謝物，其中有些具有發展成農藥替代物的潛力以對抗植物病害。先前研究指出某些土壤微生物的次級代謝物可以誘導植物抗性以減弱植物真菌病原及細菌病原所引起的病害，但是目前對於是否可以利用這些土壤微生物的次級代謝物來對抗植物病毒病害仍不清楚。植物病毒病害每年都在世界各地造成嚴重農業損失，因其無法以化學農藥防治，造成在防治上的困難。有鑑於土壤微生物的代謝物具有高度的抗病發展潛力，若能以這些代謝物誘導植物產生對病毒病害的抗病或耐病能力，則可為病毒病害防治提供一個良好策略。為了釐清這個議題，本篇論文建立一個篩選土壤微生物並且檢測其代謝物是否具有抗病毒病害能力的系統。首先，我們從台灣不同地區收集土壤並且分離能夠利用蔬菜混合物生長的土壤微生物，接著使用植物病毒Tobacco mosaic virus (TMV) 及其寄主 Nicotiana glutinosa 建立了分析抗病毒之系統。此外，我們也利用產生的病斑數目和葉片壞疽面積這兩個指標來判斷病徵的嚴重程度，並且使用水楊酸作為病毒病徵下降的正對照組以驗證兩個指標。研究結果中，我們檢驗了55種不同的土壤微生物及其代謝物之抗病毒病害能力，其中發現來自土壤樣本NTU1的真菌菌株F8最具抗TMV的潛力（減低60% 以上的病徵表現）。我們的研究成果提供了一個簡單而且快速的方式去篩選土壤微生物產生的天然代謝物質來對抗植物病毒病害。

The use of chemical pesticides has increased public concern about the negative impacts on the environment and non-specific targets, resulting in the development of alternative disease control strategies. Soil microorganisms produce a remarkable array of metabolites with broad bioactivity, some of which are potential alternatives for their anti-phytopathogenic ability. Previous studies have shown that metabolites of soil microorganisms effectively reduced plant fungal and bacterial disease symptoms by inducing plant resistance. However, the application of soil microbial metabolites on viral disease control remains largely to be explored. Plant viral diseases cause severe agricultural losses worldwide every year for the lack of effective chemical control methods. Given that bioactive metabolites of soil microorganisms are promising resources for disease control, the application of microbial metabolites may probably confer resistance or tolerance on plant to control plant viral diseases. To address this issue, we established an assay system for testing the anti-viral activity of soil microbial metabolites on plants, and isolated soil microorganisms by method described in Ko et al. (2010b). First, we collected several soil samples from different regions in Taiwan and then isolated the target soil microorganisms which can utilize vegetable mixture for growth. Second, we established a virus-plant inoculation system with Tobacco mosaic virus (TMV) and local-lesion tobacco, Nicotiana glutinosa. We used salicylic acid (SA) as positive control for symptom reduction and determined two distinct parameters including lesion number and necrotic area to quantify symptom severity. We have examined 55 metabolites derived from soil microorganisms candidates for their anti-viral activity, and found that a fungus candidate, NTU1-F8, was the best to induce resistance against TMV (about 60% of symptom redaction). The results of this study may provide a simple and effective way to discover natural substances that can induce plant resistance against various viral pathogens.