| Summary: | 碩士 === 國立臺灣大學 === 植物病理與微生物學研究所 === 101 === There were about 500 species in Cyatheaceae around the world, distributed in tropical and subtropical, and usually as important object for researching geobiography and evolution. Cyathea lepifera (J. Sm. ex Hook.) Copel.), also called scalty tree fern, member of Cyatheaceae, usually with erect and unbranched stem, and fronds arranged in a terminal crown. The world distribution of C. lepifera is centered in Taiwan, and radiated out to the surrounding areas, such as southeast part of China, Philippines, and Ryukyu . Recently, many wilted and dead trees of C. lepifera were discovered in Taiwan, called Cyathea lepifera wilt; however, the cause of the death was unknown. For the beginning of symptoms, a few of laminae turned to brownish red and withered, and withering spread with progress, until no frond remained on the terminal of stem. Dissected tree fern to reveal medulla in stem, brown and soft rot tissue was observed. C. lepifera wilt usually occurred in summer and it took about a month from symptoms revealed to dead. For researching etiology of C. lepifera wilt and choosing collection sites of diseased plants, we investigated population, information of habitat of C. lepifera, and epidemiology of wilting with geographic information system and orthophotography in Yangmingshan National Park where were native for C. lepifera. There were more than 40,000 trees estimated of C. lepifera, favor elevation between 200 and 600 meter high, middle slope, north to east aspects, and also prefers to grow in the valley where flow accumulation is greater than zero. Furthermore, in preliminary vegetation surveys showed that no significant variation was observed in the vegetation structure of C. lepifera, suggesting that companion plants may be not involved in the death of tree fern. The area which showed more severe disease incidence included Macao and Wansi, both were in the east part of Yangmingshan, and toward to northeast. Disease rate of Macao and Wansi were 18.7% and 18% for each in 2009; 30.8% and 19.1% for each in 2010; 18.4% and 23.3% for each in 2011. So we decided to collect diseased sample from Macao and Wansi after observed the phenomenon of infection in spreading with setting plots for monitoring. It’s convinced that C. lepifera wilt was caused by a new species in fungus by finishing Koch’s postulates. We thought the fungus belongs to Diaporthaceae after further molecular and morphological identification. So far, we’ve know that fungus reproduce by pycnidia and perithecia. Strategies for integrated pest management, such as pathogen eradication, applying agent for prevention ,and pathogen detection by specifi primers. Effective fungicides including thiabendazole, benomyl, kasugamycin, mancozeb, and procymidone have been identified; however, their application in the field and also disease management strategies need further evaluation.
|
|---|
