Genomic analysis of Papaya leaf distortion mosaic virus (PLDMV) and study on interaction between PLDMV and Papaya ringspot virus in papayas

• Main Authors: Hsiao-Ying Yang, 楊小瑩
• Other Authors: 洪挺軒
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/85915724528924292995

碩士 === 國立臺灣大學 === 植物病理與微生物學研究所 === 96 === Papaya is one of the tropical fruits with economic importance in Taiwan. Another conspicuous pest, Papaya leaf distortion mosaic virus (PLDMV), recently occurred in the papaya orchards in Taiwan besides Papaya ringspot virus (PRSV). The pathological and molecular characters associated with PLDMV are still unclear because of rare studies on it. This thesis was dedicated to study the genomic nature and investigate the pathogenicity of PLDMV. Several important data such as the determination of full-length genomic sequence of PLDMV, development of RT-PCR (reverse- transcription polymerase chain reaction) and real-time RT-PCR (real-time reverse-transcription polymerase chain reaction) for efficiently qualitative and quantitative detection of PLDMV, and inoculation tests for comparative pathogenicity of PLDMV on different papaya cultivars (lines) were completely presented in this thesis. The full-length genomic sequence of PLDMV (Taiwan-KS isolate) was determined (total 10,153 nucleotides) and published in GenBank (Accession number: EU233272). Based on the results of alignment, the full-length nucleotide sequences were 94.7% homologous between KS and Japanese isolate (J56P). The nucleotide alignment of individual genes demonstrated that the 3’UTR, CI and CP genes have higher homology (96.7%, 95.8% and 95.8% respectively) whereas 5’UTR and P1 genes have lower homology (86.6% and 92.2% respectively) between them. The amino acid alignment of individual genes demonstrated that the NIa-Pro and CI have higher homology (98.4% and 98.3% respectively) whereas P1 has lower homology (87.9%). Symptoms induced by PLDMV were various on different papaya cultivars (lines) such as Tainung No.2 (TN2), National Taiwan University Hybrid No.1 (NTU1), Red Lady (RL) and the genetically modified papaya against PRSV (GM). PLDMV induced symptoms including vein-clearing, leaf-distortion and fern-leaf on TN2, NTU1 and GM. On RL, PLDMV induced vein-clearing and mild leaf-distortion without fern-leaf symptoms. The multiplicative fluctuation of PLDMV on different papaya cultivars (lines) was qualitatively and quantitatively monitored by RT-PCR and real-time RT-PCR. The results showed that PLDMV could be detected 12 days post-inoculation (dpi) on TN2, NTU1 and GM papaya, and it replicated to the maximum approximately 30 dpi. PLDMV was detected 20 dpi on RL, and it replicated to the maximum approximately 60 dpi. Compared to PLDMV-infection, PRSV seemed to show better susceptibility in papayas. PRSV could be earlierly detected than PLDMV after inoculation, and it rapidly replicated to the maximum approximately 14~16 dpi. On the other hand, the results of simultaneous inoculation with PLDMV and PRSV indicated that the amount of PRSV in papayas was increased more than individual infection of PRSV, and PRSV slightly delay the multiplication of PLDMV. The results also showed that papayas co-infected with PLDMV and PRSV produced more serious symptoms than those infected individual PLDMV or PRSV. PLDMV should be not neglected in the control of virus diseases of papaya.