Nucleotide sequence analysis and detection application of the coat protein gene of Sweet potato latent virus isolated from central Taiwan

Wang, L. Y., Chen K. C., Chen, T. C., and Yeh, S. D. 2007. Nucleotide sequence analysis and detection application of the coat protein gene of Sweet potato latent virus isolated from central Taiwan. Plant Pathol. Bull. 16: 141-148. A potyvirus-like agent (isolate CY) was isolated from sweet potato with leaf symptoms of chlorotic spots and vein mottling in Chia-Yi area, Taiwan. A 1.9-kb DNA product was amplified by reverse-transcription polymerase chain reaction (RT-PCR) from infected tissues of C. quinoa using the oligo(dT) and degenerate primers for potyviruses, cloned, and then sequenced. The cDNA fragment reflected 1880 nucleotides (nts) corresponding to the 3'-terminal region of a potyvirus and the sequence comparison indicated that the isolate CY belongs to Sweet potato latent virus (SPLV). The deduced amino acid sequence was determined as 561 residues that contains a part of the 3'-terminal region of NIb gene (268 residues) and the complete sequence of coat protein (CP) gene (293 residues). The 3'-terminal region of the cDNA was determined containing a non-coding region (NCR) of 197 nts. The DAG triplet for aphid transmissibility was found at the 7-9 residues from the N-terminus of CP gene. Multiple sequence alignment of the known sequences of SPLV indicated that the CP gene and the NCR of CY isolate share 96.5 and 100% nucleotide identities, respectively, with those of SPLVTW. The phylogenetic analysis indicated that the CY isolate is closely related to Taiwan and China isolates, but distantly related to a Japan isolate. When a pair of specific primers designed from the CP gene of SPLV-CY was used for detection by RT-PCR, a 675 bp specific DNA fragment was amplified from SPLV-CY infected plants.