洛神葵癌腫病菌特性分析及防治策略開發

2016 年首次於臺東縣太麻里鄉多良村洛神葵 （Hibiscus sabdariffa Linn.） 栽培田區的植株根基部發現異常腫瘤，而後陸續於金峰鄉歷坵村、臺東市知本里與大武鄉大竹村發現類似病徵，涵蓋範圍在臺東知本以南，且經由柯霍氏法則確認此病由 Agrobacterium tumefaciens 造成。本研究進一步瞭解洛神葵癌腫病菌之特性，發現其於 20、28 和 37°C 下均能生長，較適合生長於中性偏酸性 （pH 6-7） 之環境。除了洛神葵之外，此菌尚能感染番茄、玫瑰和黃秋葵，以及田間常見野草金午時花（Sida rhombifolia Linn.） 與白花虱母子 （Urena lobata Linn.）。當接種菌量低於 106 cfu/mL 時，無法穩定地在接種部位觀察到腫瘤形成，而腫瘤大小隨接種菌量提高而增加；若將此病原菌接種於洛神葵莖頂分生組織時，可觀察到顯著大於接種其他部位所形成的腫瘤，且會造成植株矮化。以 75 % 酒精或 3 % 次氯酸鈉 （NaOCl） 溶液進行器具消毒，可以有效降低模擬摘心動作造成的癌腫病發病率。此外，透過提前施用或是在接種病原菌時同時施用四環黴素與拮抗菌 Pseudomonas protegens XH1-2a，均能有效降低腫瘤生長。本研究透過進一步分析洛神葵癌腫病菌特性，有助於瞭解洛神葵癌腫病的發病生態；篩選出的防治資材與器具消毒的方式，可用以規劃出一害物整合管理策略，未來可提供給農民作為應對此病害發生時參考，以降低此病害可能造成之損失。

Since 2016, a new crown gall disease was discovered in the commercial plantations of roselle (Hibiscus sabdariffa) in Taimali Township and later spread to Jinfong, Ziben and Dawu, covering areas in Taitung County south of Ziben. The causal agent of the disease was identified as Agrobacterium tumefaciens (Beijerinck and van Delden 1902) Conn 1942 in a previous study. Here, we found that A. tumefaciens TD1-24, the bacterial strain used in this study, was able to grow at 20, 28 and 37°C. The optimal growth pH for this bacterium was around 6-7. Other than roselle, it can also cause galls on tomato, rose and okra as well as weeds commonly found in the field, including Sida rhombifolia and Urena lobata. When A. tumefaciens TD1-24 was inoculated on the meristem of the roselle plants, significantly bigger galls were formed, leading to stunted plants. Gall formation was not stable if the inoculum was lower than 106 cfu/mL, and the size of the galls is dependent on the inoculum levels. We also found that incidence of crown gall disease can be reduced if tools used for prunning were disinfected with 75 % ethanol or 3 % NaOCl. Furthermore, gall formation was inhibited when the inoculated roselle seedlings were pretreated with tetracycline or Pseudomonas protegens XH1-2a 7 days before inoculation or treated at the time of inoculation. Therefore, characterization of the causal agent of roselle crown gall could help us further understand its ecology and epidemiology. The chemical and biological agents identified as well as the cultural control method developed in this study could be used to generate an integrated pest management strategy as references for farmers to manage this disease and reduce the potential economic loss in the future.