Detection And Sequence Diversity Analysis Of Viroids Isolated From Peach

Peach tree are widely cultivated in majority area of China, according to statistics up to 2006, peach cultivating area in China were 677,000 hectares. In recent years along with peach tree industry development, the infection of viroids in peach was severe. Viroids in peach result in dapple fruit and blotches or yellow mosaics on leaves, which has serious influence on peach fruits economic value and fruit tree's industry. At present two kinds viroids were reported infected peach. Hop stunt viroid (HSVd) and Peach latent mosaic viroid (PLMVd). PLMVd had been already reported on peach tree of China, but HSVd has no one.The peach tree origins from China, so geographical distribution analysis of these two type viroids in partial provinces of China as well as sequence diversity analysis of HSVd - peach has important significance to detect, prevent, control the viroid disease, and also the research in origin and pathogenicity of viroids.RNA was extracted from 97 peach samples, contained 50 samples of peach leaf (L1-L50) and 6 samples of peach fruit (F1-F6) which were collected from Beijing, 41 samples of peach bark (B1-B41) from Hebei, Shandong, Shannxi, Guangxi, Beijing, Xinjiang, Fujian, Gansu provinces of China. The sample were detected by Dot-blot hybridization, RT-PCR and Bioassay. HSVd was detected in 18 samples collected from Beijing, Shannxi, Xinjiang, Fujian, and Gansu. The infection rate was 18.6 %. Those methods were able to detect HSVd in peach, and have consistent results from all three methods. PLMVd was detected in 88 samples collected from Beijing, Shannxi, Xinjiang, Hebei, Shandong, Guangxi and Gansu by Dot-blot hybridization. The infection rate was 90.7 %.Seventeen Peach samples collected from Beijing, Shannxi, Xinjiang and Gansu were mixed infected by HSVd and PLMVd, the samples from Fujian were only positive of HSVd, and samples from Hebei, Guangxi and Shandong were only positive of PLMVd.Nine samples (L19, L42, L48, B6, B18, F1, F4, F5, F6) were selected from 18 positive samples of HSVd, HSVd were cloned from these samples. 22 sequence variants were obtained. The clones showed 93%～100% homology when compared with HSVd reported in GenBank. The results suggested that the sequence variants of HSVd in peach from China were relatively conserved, there was no clear diversity among varieties and regions.Twenty-two HSVd sequences were deposited into GenBank, and the GenBank accession number are DQ362900,DQ362902～DQ362903,EF080841～EF080859. This is the first report on HSVd from peach in China.