Identification and characterization of a potyvirus causing leaf mosaic on Melothria pendula L. in Taiwan

• Main Authors: Peng, Kuan-Chen, 彭冠甄
• Other Authors: Chen, Tsang-Hai
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/hcfwt7

碩士 === 國立屏東科技大學 === 植物醫學系所 === 105 === Malothria (Melothria pendula L.) originated from the northeast of Amarica is a wild cucumber of the family Cucurbitaceae. It invaded to Taiwan in about year 2000 and was found in central area of Taiwan in the record. An undescribed virus diease that exhibited mosaic on leaves of malothria was found in 2012 at Pingtung county, Taiwan. In the beginning stage the leaves showed yellow vein mosaic symptom. Later, the leaves deformed and showed green island mosaic. The symptoms can be seen all year round. A flexuous filamentous virus of 700-800 nm in particle size was observed by EM in crude saps of field disease malothria. The virus was isolated by mechanical inoculation through Chenopodium quinoa and C. amaranticolor. The thermal inactivation point of the virus was 55-60℃, dilution end point was 10-4. Pinwheel-shaped and laminated inclusion bodies typical of potyvirus infection were found in cytoplasm from the tissue of disease malothria and the local lesion of C. quinoa. The virus had a very narrow host range restricted to 7 species in cucurbitaceus and chenopodiaceous plants among 72 test plant species belonging to 17 families. It caused local lesions, leaf deformation and mosaic symptom on host plants. Aphis gossipii Glover, Myzus persicae Sulzer, and Lipaphis erysimi Kaltenbach were able to transmit the virus from disease malothria in non-persistent manner. The disease was not transmitted by seed-borne test. The molecular weight of capsid protein (CP) of the virus was estimated 35 kDa. In order to further characterize the virus, the CP gene of malothria virus isolate was cloned, sequenced and analyzed. A sequence of 837 nucleotides (nts) was found and blast with Genbank database, the closest genetic relationship with the virus was Zucchini yellow mosaic virus. The percentage of nucleotide identity of CP gene was 92.0% comparing to ZYMV isolates from TW-NTML1(Acc. No.AF127932) and CU(Acc. No. AJ307036). Similarly, percent identities of amino acid sequence of CP gene revealed 97.5% with five ZYMV isolates of 13spno4(Acc. No. HM005311). In conclusion, the results indicated that the virus isolated from malothria showing mosaic symptom is a ZYMV isolate of Potyvirus genus. This is the first report about the viral disease of malothria in Taiwan. Key Words：Melothria pendula L., viral disease, Zucchini yellow mosaic virus, ZYMV