水稻種子病原菌 Monographella Albescens 之分離及生理研究

Studies of Isolation and Physiology of Monographella Albescens Pathogen from Rice Seeds

臺灣地處亞熱帶，屬於高溫多濕的海島型氣候，適合一些稻作病原菌之繁殖及生長，因此導致每年因稻作病害引起的經濟損失達 6%左右。本研究自台東縣池上鄉新興育苗場之高雄 139 號水稻種子，獲得一株代號為 Ma-1027 之分離菌株。並針對 此菌株進行觀察與研究。首先以光學顯微鏡觀察 Ma-1027 之孢子，得知其外觀呈現透明橢圓之紡綞形，具有 1-2 隔膜，孢子大小約為 11-21×4-8μm2 。再以分子生物技 術鑑定，分別使用 18S-F/28S-R 和 A1-16S-23S-F/A1-16S-23S-R 引子對，進行 Ma-1027 genomic DNA 之聚合酶連鎖反應（Polymerase chain reaction, PCR）增幅及水平電泳膠體分析。結果顯示，Ma-1027 的 PCR 核酸產物之大小約為 650 bp。將 PCR 產物之核 苷酸序列進行譯讀與比較，結果顯示 Ma-1027 與 NCBI 中的 Monographella albescens isolate CIAT 11(AJ132506.1)之 5.8S rRNA gene、internal transcribed spacer 1 (ITS1) 及 internal transcribed spacer 2(ITS2)核苷酸序列相同度達 100%。將 Ma-1027 可以 接種至高雄 139 號水稻葉面，可以產生相同之病徵，顯示此分離培養菌株之穩定性。 在 Ma-1027 菌株之生理研究方面，培養條件為培養溫度 20℃，培養基添加果糖（fructose）作為碳素源，硝酸鈉為氮素源，pH 6，對菌絲的生長條件最佳。以 39 個水 稻品種進行感病性測試，結果顯示，全部皆對 Ma-1027 不具抗病性。最後以藥劑進 行室內篩選，結果顯示，以 25%撲克拉乳劑(Prochloraz)稀釋 1000 倍、34%殺紋滅達 樂溶液（Hymerxazol+Metalaxy）稀釋 1000 倍、40%亞賜圃乳劑（Isoprothiolane）稀釋 1000 倍及 10%菲克利乳劑（Hexaconazole）稀釋 1500 倍之處哩，對 Ma-1027 菌絲生長之抑制性較強。

Taiwan is located at tropical and subtropical areas belonging to island weather with high temperature and humility which is suitable for pathogens propagation and infection to rice crop. Every year the economic loss caused by rice diseases is about 6%. A fungal isolate named as Ma-1027 was isolated and cultured from seeds of Kaohsiung 139 rice variety at Hsing-sing rice seedling production station in Chihshang area of Taitung county. Under microscope observation, conidia of Ma-1027 were observed as rhombusshaped conidia with 1-2 septa and size of 11-21×4-8μm2 . Genomic DNA of Ma-1027 were further identified and analyzed by PCR amplification with 18S-F/28SR primer. Sizes of PCR DNA products were estimated about 650bp. The results of comparison of nucleotide sequences of PCR DNA products indicated that Ma-1027 was close to Monographella albescens isolate CIAT 11(AJ132506.1) in NCBI with 100% identity and this is a first report in Taiwan. Infectivity of Ma-1027 was confirmed by inoculation on Kaohsiung 139 rice variety. The optimal physical conditions for mycelial growth of Ma-1027 were determined at 20℃, and medium with fructose carbon source, NaNO3 of nitrogen source and pH 6 value. Thirty nine rice varieties determined by Ma-1027 inoculation showed that no resistant variety was found. The result of agrochemicals screening in laboratory indicated that 25% prochlorage, 34% Hymerxazol+Metalaxy, and 40% Isoprothiolane with 1,000 time dilution, 10% Hexaaconazole with 1,500 time dilution had good inhibition on mycelial growth of Ma-1027.