Analyses of the Coat Protein Genes of Papaya Ring Spot Virus W Type Isolates from Different Areas of Taiwan

• Main Authors: Wang, Ju-Jung, 王如蓉
• Other Authors: Yeh Shyi-Dong
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/05460395386474296160

碩士 === 國立中興大學 === 植物病理學系 === 84 === Papaya ringspot virus (PRSV), a member of the Potyvirus genus, contains two major groups, type P ( PRSV P) and type W (PRSV W) virus. The host range of PRSV W strains is limited to Chenopodiaceae and Cucurbitaceae, whereas P type strains infect Cariceae (papaya) in addition. In order to develop transgenic cucurbits with resistance to PRSV W in Taiwan, typical PRSV W isolates from the island were collected and the variability in the nucleotide and amino acid sequences of the CP genes were analyzed. Twelve isolates from the forty ELISA positive samples, collected from six cucurbit crops from different areas of Taiwan, were identified by host reactions and serology tests as typical W type virus isolates. They did not infect papaya but were serologically indistinguishable from type P isolates when tested against the antisera to PRSV P type or PRSV W type. In order to analyze the polymorphisms of the CP genes of the 12 PRSV W type isolates from Taiwan and other reported PRSV W and P type viruses, digestion patterns of RT-PCR products,which were amplified from the N-terminal half of the CP genes, with RsaI, AluI and NlaIII were compared. The results showed that most of the 12 PRSV W isolates from Taiwan were closely related to PRSV P- YK, a P type strain from Taiwan, and P-PD, a P type strain from Thailand,and far apart from P-HA, a P type strain from Hawaii, and W-FL, a W type strain from Florida. To further analyze the variation of the CP genes of PRSV W isolates from Taiwan, three isolates, PRSV W-CI (from Chiayi), W-TN (from Tainan) and W-PT ( from Pingtung), were chosen for cDNA cloning for determination of their CP gene sequences. Comparison the three isolates of Taiwan with each other, indicated that they shared 96.37-96.99% and 94.46-96.74% nucleotide and amino acid identity, respectively, and the nucleotide identity of the 3' non-coding regions were 98.56-99.04%, indicating that the three isolates were closely related strains of the same virus. Comparison of the three W isolates from Taiwan with other reported W isolates of W-FL (from Florida) and W-AU (from Australia), and P isolates of P- YK (from Yung Kang, Taiwan), P-HA (from Hawaii), and P-FL (from Florida) revealed that the nucleotide identity of the CP genes of the three W type isolates from Taiwan shared higher percentages of 95.93-96.64% with P-YK, another P type isolate from Taiwan, they shared lower percentages of 90.59-91.97% with other non-Taiwan PRSV W and P type isolates. In terms of amino acid identity of the CP genes, the three PRSV W type isolates from Taiwan, shared 95.21-96.16% with PRSV P- YK. The comparison of non-Taiwan W and P type isolates showed that they had 95.12-99.3% amino acid identity. The comparison of the 3' non-coding regions of the eight PRSV isolates, revealed that the three PRSV W isolates from Taiwan shared 97.21-98.08% nucleotide identity with P-YK, whereas they shared only 88.51-93.3% nucleotide identity with other non-Taiwan PRSV P and W isolates. The sequences analyses indicated that the relationships among these W and P type isolates could be divided into two groups, one contained PRSV W-CI, W-TN, W-PT and P-YK, the other one contained PRSV W-AU, W-FL, P-HA and P-FL. These coupled with enzyme-digestion polymorphisms indicated that the CP genes of the three W type isolates from Taiwan were closely related to P-YK(a Taiwan isolate) and far apart from W and P type isolates in other different geographic areas. Our results also implicate that degrees of variation of the CP genes do not follow major differences in host specificity, such as papaya or non-papaya infecting, but are more closely corresponding to geographic distribution.