蓮霧黑腐病菌之鑑定與致病力比較

Identification and virulence comparison of pathogens cuasing fruit black rot of wax apple

蓮霧黑腐病為蓮霧上常見的病害，發病初期於果實上造成水浸狀病徵，而後水浸狀擴大至整顆果實，並在果實表面產生大量黑色柄子殼，使果實呈現黑色外觀，之後逐漸失水呈木乃伊狀。本研究收集了來自高雄、嘉義、南投及屏東等產地的罹病果實，並分離菌株，經人工接種後確認收集到的所有菌株皆有病原性，病原菌經形態鑑定為Lasiodiplodia屬及Neofusicoccum屬，並進一步利用核糖體核糖核酸內轉錄區間隔(rRNA-ITS)、β-微管蛋白(TUB2)、轉錄延伸因子1α（TEF1α）以及RNA聚合酶Ⅱ第二大次單元(RPB2)之序列，進行多基因序列鑑定所收集的菌株，分別有L. theobromae、L. pseudotheobromae及N. parvum等三種。以此三種菌之代表菌株進行比較，探討不同溫度下三種菌對於蓮霧果實的感染力。結果顯示32 ~ 37°C環境下L. theobromae與L. pseudotheobromae的感染較N. parvum快，且37°C下明顯不利於N. parvum的感染；三種菌在24°C下的感染能力相當，但在16°C下的感染能力皆顯著受到抑制，在8°C環境下則完全無法感染。其中L. pseudotheobromae及N. parvum引起蓮霧果實病害為世界首次紀錄。

Fruit black rot of wax apple is a common disease. The initial symptom is a water soaking lesion. Later, the lesion expands over the entire fruit. As a huge amount of black pycnidia is produced on the surface of infected fruits, the fruit become black. The diseased fruit graduately lose water and eventually become mummified. This study isolated pathogens of diseased wax apples collected from Kaoshung, Chiayi, Natou and Pintung. Artificial inoculation confirmed that all isolates were pathogenic. All pathogens were morphologially identified as members of Lasiodiplodia and Neofusicoccum. Further identification was carried out by multigene sequence analysis based on sequences of internal transcribed spacer (ITS),β-tubulin (TUB2), translation elongation factor 1-alpha (TEF1α), and RNA polymerase subunit II (RPB2). Three species were revealed: L. theobromae, L. pseudotheobromae, and N. parvum. Virulence of the representative isolates of each specie was compared at different temperatures. L. theobromae and L. pseudotheobromae colonized fruit faster than N. parvum at 32 - 37°C. Colonization of N. parvum was significantly impeded at 37°C. The three species displayed comparable virulence at 24°C, decreased colonization at 16°C, and complete loss of infection ability at 8°C. This is the first report globally that L. pseudotheobromae and N. parvum cause fruit rot of wax apple.