Molecular and biological characteristics of peach latent mosaic viroid mosaic isolate
Peach latent mosaic viroid(PLMVd)is an important viroid infecting peach trees.PLMVd can cause various leaf symptoms including mosaic,yellowish and calico,etc.At present,the mechanism of PLMVd infec-tion causing mosaic leaves is unknown.In this study,86 full-length PLMVd sequences,in size of 336-338 nt,were isolated and cloned from the mosaic(M)and asymptomatic(N)leaves of nectarine trees collected in the field in China.By DnaSP 5.0 analysis,31 haplotype(variant)sequences were obtained in the cloned sequences.The haplotype diversity(Hd)was relatively low as 0.79 for M isolates,while was high as 0.90 for N isolates.Compared with N isolates,sequence analysis showed that the sequence variation of M isolates mainly occurred in five regions of the whole sequence.MY1 haplotype sequence was dominant among those of M isolates,which clustered in phylogenetic group I with a few other variants and shared 89.4％identity with that of P1.148,a typical peach calico isolate.Through a comparative study of PLMVd cDNA infectious clones,gene synthesis and inoculation methods,the infectious PLMVd diploid cDNA clone construction and effective inoculation methods were established.The constructed MY1 diploid cDNA recombinant plasmid can infect the Prunus davidiana Franch systematically and exhibit typical mosaic symptoms after high-stressed stems slashing inoculation.The results will build a foundation for further study about the molecular mechanism of PLMVd inducing peach mosaic symptom.
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