Detection of sweet potato viruses in Yunnan and genetic diversity analysis of the common viruses

Abstract:

[Objective] To determine the sweet potato virus species in Yunnan and analyze the genetic diversity of the main viruses. [Methods] Two hundred seventy-nine sweet potato samples with virus-like symptoms collected from 16 counties/cities in Yunnan Province were tested by RT-PCR/PCR using virus-specific primers for 8 sweet potato viruses. The RT-PCR amplicons of SPFMV, SPVC and SPVG from selected samples were cloned and sequenced. The alignments and phylogenetic analyses were performed with the MEGA 5 software package. [Results] Six viruses, sweet potato chlorotic fleck virus (SPCFV), sweet potato feathery mottle virus (SPFMV), sweet potato leaf curl virus (SPLCV), sweet potato virus C (SPVC), sweet potato virus G (SPVG) and sweet potato virus 2 (SPV2), were detected in 123 samples (44.1%) from 14 counties/cities except Puer and Xianyun. Of all the detected viruses, SPVG was detected in 109 samples (39.1%), SPFMV in 75 samples (26.9%), SPVC in 69 samples (24.7%), and SPLCV just in one sample (0.4%). Mixed infections of 2–5 viruses were common (31.90%) in Yunnan. Among the mixed infections, most of them were caused by 2–3 viruses. Only 34 samples (12.2%) were caused by one virus, however, no single infection was detected for SPCFV, SPLCV and SPV2. [Conclusion] Sequenced analysis showed that the Yunnan isolates of SPFMV belonged to three strains, EA strain, O strain, and another strain different from EA, O and RC. Both SPVC and SPVG isolates were divided into three groups, and most of the Yunnan SPVG isolates were in the group I.