Identification And Sequence Analysis Of Viruses Infecting Strawberry Seedlings In Some Provinces Of China

With the increase of greenhouse strawberry area and the production and trade of asexual reproductive seedlings between different regions,the occurrence and prevalence of strawberry viral disease are also increasing and becoming more and more serious.To identify virus infecting strawberry seedlings from Beijing,Hebei,Inner Mongolia,Sichuan,Liaoning,Yunnan and Shannxi,small RNA deep sequencing were used to detect the sequences of viruses in strawberry seedling samples and then specific viruses were verified by RT-PCR and sequence analysis further.The results showed that strawberry vein banding virus(SVBV),strawberry mottle virus(SMo V)and strawberry mild yellow edge virus(SMYEV)only were detected in ‘Benihoppe’ cultivar plants tested.Coinfection of different viruses were detected in some strawberry seedling samples.The detection rate and virus species of ‘Benihoppe’ cultivar plants tested from different provinces are significantly different.The partial nucleotide sequence homology of SVBV and SMo V isolates from different provinces was 97.98%～99.8% and 98.12%～99.34%,respectively.The cp gene sequence of SMYEV Liaoning isolate lnhy26 shared 99.02% identity with Gansu isolate sy02.To further identify virus infecting strawberry seedlings of 33 cultivars from Beijing and Hebei,RT-PCR were used to detect the sequences of viruses in strawberry seedling samples.The results showed that strawberry vein banding virus(SVBV),strawberry mottle virus(SMo V),strawberry mild yellow edge virus(SMYEV)and cucumber mosaic virus(CMV)were detected 33 cultivars plants tested.8 different types of virus coinfection were detected in the tested samples.There were significant differences in virus detection rate and virus species among strawberry seedlings of different varieties.The partial nucleotide sequence homology of SVBV and SMo V isolates from strawberry seedlings of different cultivars was 98.51%～100% and 91.11%～100%,respectively.The cp gene sequence of SMYEV Beijing ‘Asia’ isolate bjash6 shared homology 98.31% with that of Gansu isolate sy02.The nucleotide sequence homology of partial cp gene of two CMV isolates from different varieties was100%,belonging to subgroup ⅠA.In order to identify the molecular variation of SMYEV-lnhy26,a 5 890 nt nucleotide sequence of SMYEV-lnhy26 was obtained.The nucleotide sequence of ORF1～ORF5 gene shared 84.29%～99.02%and amino acid sequence shared 86.87%～99.17% homology with the isolates registered in Gen Bank.No recombination event was found in gene recombination analysis.The content of SVBV or SMo V in different leaves of the same text plant was significantly different by real-time fluorescent quantitative PCR.The content of SVBV was higher in leaves far away from the growing point,but the content of SMo V was opposite.