泡桐抗耐簇葉病之評估與健康管理研究

台灣泡桐早年曾被譽為台灣的綠色黃金，並且在1960-1970年代被廣泛種植。然而1980年代，台灣泡桐造林地普遍受到泡桐簇葉病 (Paulownia Witches' broom, PaWB)的為害，嚴重摧毀了泡桐產業。泡桐簇葉病的病原是植物菌質體 (phytoplasma)，屬蟲媒傳播之系統性病害，同時也可經由受感染的無性繁殖材料快速傳播。泡桐簇葉病目前尚無有效的藥劑防治措施，本計畫針對泡桐簇葉病開發了PCR診斷方法，配合專一性引子對，可用於簇葉病發病生態及抗病品種篩選的研究。針對不同泡桐品系苗木進行接種試驗，並使用PCR技術監測菌質體增殖的情形，結果顯示接種並確認感染的泡桐苗木不同部位的菌植體濃度以葉脈最高，其次為莖部、葉肉及皮層含量最低。接種測試結果顯示台灣泡桐完全不抗病，貴州泡桐以及白桐與貴州泡桐的雜交品系則呈現不同程度的耐抗病性。顯示接種測試配合PCR檢測，可以加速篩選耐抗病的雜交泡桐品系。為了解泡桐簇葉病四季發病情形，並監測菌質體在泡桐植株內的周年變化，自2014年2月開始至2015年6月為止，針對台東樣區17株樣木進行逐月採樣，PCR結果顯示菌質體數量在泡桐植株內有隨季節消長的情形。菌質體含量以及發病率在夏季達到高峰，且PCR檢測可以在病徵未出現前偵測到菌質體。經由田間採集以及人工餵蟲傳播試驗證實茶翅椿(Halyomorpha mista)是泡桐簇葉病的媒介昆蟲。田間族群調查發現，茶翅椿族群數量在一年中有兩個高峰期，分別出現在3至4月及8至10月間。此外在太麻里試驗區亦觀察到另一種可能的媒介昆蟲黃斑椿象（Erthesina fullo)。藉由PCR檢測技術進行田間泡桐林木及媒介昆蟲帶原率監測，並持續追蹤媒介昆蟲族群變化，可以做為防治最佳時機之判斷依據進而擬訂防治對策。雖然病蟲害監測可以協助早期防治泡桐簇葉病，然而，選育優良的抗耐病泡桐品系以及培育健康種苗，將會是建立健康泡桐產業更重要的關鍵。 Paulownia taiwaniana is a fast-growing timber species, which was earlier hailed as Taiwan’s green gold and planted extensively during the 1960s and 1970s. However, in the 1980s, paulownia witches’ broom (PaWB) infection destroyed paulownia plantations and resulted in significant economic losses. Phytoplasma is the causative agent of PaWB, which can be transmitted by vector insects and infected propagation materials. So far, no effective chemical treatment strategy is available for PaWB control. In this project specific and effective PCR primer of PaWB phytoplasma was designed and applied for PaWB detection, field research and resistant breeding. Phytoplasma was artificially inoculated onto healthy paulownia seedlings to evaluate resistance or tolerance of different paulownia clones to PaWB. PCR with specific PaWB primers was carried out to monitor the distribution and concentration of phytoplasma in inoculated paulownia seedlings. The PCR results indicated concentrations of PaWB in mesophyll, petioles, veins and bark of infected paulownia seedlings were from high to low, respectively. Artificial inoculation of test paulownia seedlings indicated P. taiwaniana plants were susceptible, however, seedlings of P. fortunei and P. kawakamii x P. fortunei hybrids showed varying degrees of tolerance to PaWB. The results showed artificial inoculation testing with PCR testing accelerate screening paulownia strains resistant or tolerant to PaWB. 17 paulownia plants in Taitung area were sampled monthly from February 2014 to June 2015 to evaluate the infection rate and variation of phytoplasma concentration in paulownia plants. PCR results indicated phytoplasma content in paulownia plants showed seasonal fluctuation. Phytoplasma content and incidence rate peaked in the summer, and the PCR test can detect the early presence of phytoplasma before symptoms occurred. The results of field collection, of artificial feeding test, and PCR test confirmed Halyomorpha mista as an insect vector could sucessfully transmitted phytoplasma. Field tracking indicated that the population of H. mista peaked in March to April and August to October, repectively. Meanwhile, a yellow-spotted stink bug, Erthesina fullo, was observed in Taitung sample area, and suspected as another possible insect vector of PaWB. Information provided by monitoring the population change of vector insects and using PCR technique to monitor phytoplasma infection rate of paulownia plantations and of vector insects can be used to judge the best time of prevention and to develop better disease and pest control strategies. Pest and disease monitoring can help early prevention of PaWB, however, to establish a healthy paulownia industry, breeding of elite disease-resistant paulownia clones and nurturing healthy seedlings, will be the more important key.

台湾泡桐（Paulownia taiwaniana）是一种速生用材树种，早年曾被誉为台湾的绿色黄金，并于1960至1970年代被广泛栽植。1980年代起，台湾泡桐造林地普遍遭受泡桐簇叶病（Paulownia Witches' broom, PaWB）为害，产业遭受重创。泡桐簇叶病的病原为植物菌质体（phytoplasma），属于虫媒传播的系统性病害，亦可通过受感染的无性繁殖材料快速扩散。目前针对泡桐簇叶病尚无有效的药剂防治手段。
本计划针对泡桐簇叶病开发了配套专一性引物对的PCR诊断方法，可用于簇叶病发病生态研究及抗病品种筛选。研究团队针对不同泡桐品系苗木开展接种试验，并借助PCR技术监测菌质体增殖情况。结果显示，经接种确认感染的泡桐苗木中，菌质体浓度以叶脉最高，其次为茎部，叶肉与皮层浓度最低。接种测试结果表明，台湾泡桐完全感病；贵州泡桐（Paulownia fortunei）以及白桐（Paulownia kawakamii）与贵州泡桐的杂交品系则表现出不同程度的耐病性与抗病性。由此可见，接种测试配合PCR检测，可加速耐抗病杂交泡桐品系的筛选工作。
为厘清泡桐簇叶病的年度发病规律，并监测菌质体在泡桐植株内的周年变化，研究团队于2014年2月至2015年6月期间，针对台东样区的17株样木开展逐月采样。PCR检测结果显示，菌质体在植株内的数量随季节消长：菌质体含量与发病率于夏季达到峰值，且PCR检测可在病征显现前检测出菌质体的存在。
通过野外采集与人工饲虫传播试验，证实茶翅椿（Halyomorpha mista）为泡桐簇叶病的媒介昆虫。野外种群调查发现，茶翅椿的种群数量一年存在两个高峰期，分别为3至4月及8至10月。此外，在太麻里试验区亦观测到另一种疑似媒介昆虫——黄斑椿象（Erthesina fullo）。借助PCR检测技术开展野外泡桐林木及媒介昆虫带原率监测，并持续追踪媒介昆虫的种群变化，可作为判断最佳防治时机的依据，进而制定防治策略。
尽管病虫害监测可助力泡桐簇叶病的早期防治，但要建立健康可持续的泡桐产业，选育优良抗耐病泡桐品系并培育健康种苗，才是更为关键的核心。