Diagnosis and Molecular Pathological Character of Citrus Viroids in Taiwan

• Main Authors: Huai-Li Lu, 盧懷力
• Other Authors: Tang-Long Shen
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/79351709924922466290

碩士 === 國立臺灣大學 === 植物病理與微生物學研究所 === 101 === Viroids are the infectious RNA that lead to various plant growth disorder. Ranging from 250 to 400 nt, they are single stranded and closed covalently, forming a secondary structure. In spite of the simplicity of genome composition, viroids is of importance for the economic loss caused by them, although the pathogenesis and interaction between plant and viroids is rarely understood. Citruses are one of the most important fruit in economy. In many place citruses suffer from viroid disease. Citrus Exocortis Viroid (CEVd) and Hop Stunt Viroid (HSVd) are the two major citrus viroids, transmitted by mechanical injury or grafting. Viroids can be detected after TRIzol extraction detected by RT-PCR with primer designed according to conserved sequence. According to quantification in CEVd-infected tomato, new leaves contain more CEVd quantity than it in old ones yet less CEVd quantity than it in stems. Detection is available in lab inoculating indicators as well as field citrus sample. Since the last indigenous report was in 1975, detection to citrus in places in Taiwan, including Douliou, Hualian, Hsinchu, Pingtung, was performed. The result revealed there are two more citrus viroids(Citrus dwarf viroid, Citrus bark cracking viroid) that exist in Taiwan. Tomatoes are inoculated as indicator for pathogen maintenance and disease sieve. Cloning and Sequencing CEVd is necessary. The CEVd master sequence in Douliou field has been published from China and Japan; this result was probably due to geographical distribution. Seasonal sample collection reveals probable CEVd population change in accordance to temperature. Qiantitative result shows seasonal dynamics of CEVd. Therefore, heat treatment to indicators reveals that CEVd titer reduced in high temperature. To study the possible host of CEVd, the pathogenicity of CEVd to cultivars of tomato was test. No significant phenotype change was observed. As well, the other viroid of Tomato, Tomato Chlorotic Dwarf Viroid (TCDVd) which shares high similarity of sequence and host, was studied for distinguishing theses two. Inoculation of TCDVd and detection by RT-PCR and qPCR were done.