Viruses Dectection Of Sweet Potato Viral Diseases In Guangxi Province And Complete Genome Sequences Analysis Of Sweet Potato Feathery Mottle Virus And Sweet Potato Leaf Curl Virus

Investigation on sweet potato viral diseases were conducted in 6 cities in Guangxi Province including Nanning, Chongzuo, Yulin, Beihai, Hechi, and Guilin. The results showed that the symptoms of sweet potato viral diseases were various including vein clearing, yellow vein, mosaic, shrinkage, leaf rolls and chlorotic spot etc. Sweet potato viral diseases were found in all places where investigations were carried out, the disease incidence rate were between 10%-80%.127 sweet potato samples with viral disease-like symptom were collected and examined by PCR and RT-PCR assays using 12 viruses primer pairs. Sequencing and BLAST analysis found out that there are 11 species of viruses infecting sweet potato in Guangxi Province,10 of them are RNA viruses including:Sweet potato feathery mottle virus (SPFMV); Sweet potato chloroticstunt virus (SPCSV); Sweet potato virus G (SPVG); Sweet potato mild speckling virus (SPMSV); Sweet potato virus C (SPVC); Sweet potato chlorotic fleck virus (SPCFV); Cucumber mosaic virus (CMV); Sweet potato vein mosaic virus (SPVMV); Sweet potato latent virus (SPLV); Sweet potato mild mottle virus (SPMMV) and one DNA virus that is Sweet potato leaf curl virus (SPLCV). Among 127 sweet potato samples, the detection positive reaction rate of 11 species of viruses above was 5.51%-37.79%.By using RT-PCR and RACE assays, Sweet potato feathery mottle virus Guangxi isolate (SPFMV-GX) genome had been cloned. Genome analysis showed that nucleotide sequence of SPFMV-GX was RNA with 10895 nucleotides in length, containing a single open reading frame (ORF) and encoded a poly-protein with 383.4 kDa molecular weight.5’ untranslated region (UTR) contained 116 nucleotides while 3’-UTRcontained 299 nucleotides. Full genome sequence of SPFMV was analyzed and compared by using BLAST on NCBI. Result showed that nucleotide sequence identity among SPFMV isolates was between 87.9%-93.3%, in which SPFMV-GX showed the highest sequence identity with SPFMV-Spain (KU511268) from Spain, up to 93.3%. Phylogenetic analysis among 13 full-length sequences of viruses was performed by using BioEdit to compare relationship of SPFMV-GX with other SPFMV isolates and some members of Potyvirus. Result showed that SPFMV-GX have closer relationship with SPFMV-Spain isolate than other viruses.By using PCR assay, Sweet potato leaf curl virus Guangxi isolate (SPLCV-GX) genome had been cloned. Genome analysis showed that nucleotide sequence of SPLCV-GX was RNA with 2828 nucleotides in length, containing 6 open reading frames (ORFs), each of which encoded a protein with molecular weight of 14.5 kDa,29.4 kDa,40.7 kDa,16.7 kDa,16.8 kDa, and 17.4 kDa respectively. Full genome sequence of SPLCV-GX was analyzed and compared by using BLAST on NCBI. The result showed that sequence identity among SPLCV isolates was between 92%-96.8%, in which SPLCV-GX showed the highest sequence identity with SPLCV-Shandong isolate (KF040466) from China, up to 96.8%. Phylogenetic analysis was performed by using BioEdit to compare relationship of SPLCV-GX with other SPLCV isolates and some members of Begomovirus. Result showed that SPLCV-GX have closer relationship SPLCV-Shandong isolate than other viruses.