Identification Of Viruses Infecting Pepper In Guangdong And Evaluation Of Control Effect Of Plant Virus Pesticides

Pepper is an important cash crop, and viral disease is one of the major diseases of pepper production in China. Up till present, there are 28 viruses to be identified infecting pepper in China. Guangdong is one of major pepper growing areas in China, and pepper virus disease occur very seriously, but there is no systematic investigation and identification viruses infecting pepper in Guangdong Province. In eight main pepper-growing areas of Guangdong, pepper virus disease was surveyed and diseased samples were collected. The viruses were identificated by small RNA deep sequencing and RT-PCR detection technology. Genome sequence of Chilli veinal mottle virus(Chi VMV) was cloned and sequenced, and its pathogenicity was determined. The control effect of 16 virus pesticides on pepper virus diseases was also evaluated. The major results as follows:1. Pepper virus diseases was suveyed in 8 pepper-growing areas, Maoming, Meizhou, Shaoguan, Foshan, Guangzhou, Huizhou, Jiangmen and Zhanjiang in Guangdong Province. The pepper virus diseases occurred in all of the above-mentioned areas, and caused loss with the disease rate of 5% to 30%, and even 100%.The main symptoms of diseased plants in the fields exhibited mosaic, leaf deformity, shrinkage, bubbly and so on.2. Using small RNA deep sequencing technology and comparative analysis to identify the viruses in pepper samples, eighteen viruses were detected in seven mixed samples collected from Maoming, Meizhou and Shaoguan, respectively. The viruses included Pepper mild mottle virus(PMMo V), Bell pepper endornavirus(BPEV),Tobacco mild green mosaic virus(TMGMV), Chilli veinal mottle virus(Chi VMV), Pepper veinal mottle virus(PVMV), Cucumber mosaic virus(CMV), Pepper yellow leaf curl virus(PYLCV),Chilli ring spot virus(Chi RSV), Potato virus Y(PVY), Capsicum chlorosis virus(Ca CV), Broad bean wilt virus-2(BBWV-2), Pepper cryptic virus(PCV), Beet western yellows virus(BWYV), Tobacco vein-clearing virus(TCTV), Pepper vein yellows virus( Pe VYV), Nicotiana tomentosiformis endogenous pararetrovirus(Nto EPRVs)and Gloxinia tospovirus(Glotospov). According to the results of small RNA deep sequencing and corresponding viral genome sequences in Gen Bank, two pairs of primers for each virus were designed, respectively to detect and verify viruses in the sequenced samples by RT-PCR. The target fragment of 17 viruses except Lyc EPRVs were successfully amplified from the samples. The six viruses, PYLCV, BWYV, TCTV, Pe VYV, Glotospov and Nto EPRVs to infect pepper have not been reported to infect peppers and the others eleven viruses to infect pepper have been reported in mainland China. These results showed that the dominant viruses on pepper in Guangdong were PVMV, Chi VMV, PVY, PMMo V and Pe VYV.3. One of two pairs of primers for better amplifying every virus was selected to detect 125 suspected pepper samples collected from 8 areas in Guangdong Province by RT-PCR. The results showed that 124 samples were positive, and 18 viruses were identified from the samples. According to detection probability, these viruses in proper order were Nto EPRVs(57%), PMMo V(44%), BPEV(33%), TMGMV(31%), Chi VMV(30%), PVMV(30%), Pe VYV(26%), CMV(18%), PYLCV(17%), Chi RSV(17%), PVY(15%), Ca CV(14%), BBWV-2(10%), Glotospov(10%), Pe CPV(9%), TMV(4%), BWYV(3%) and TCTV(2%). The viruses belonged to Potyvirus predominated and the dominant virus in different areas were also different. Only 9 in 125 samples had one virus, and the other samples had 3 or more viruses. The detection rate of mixed infection was 93.55%. These results indicated that viruses mixed infection in pepper was serious in Guangdong.4. The genome of Chi VMV isolate Guangdong(Chi VMV-GD)was cloned and sequenced. It had 9721 nt(Gen Bank Accession No. KU987835), contained a 9270 nt single open reading frame(ORF)and encoded a 3089 aa protein. Chi VMV-GD had the closest relationship(homology rate 96.9%)with Hainan isolate, and less related with Sichuan isolate and Yunnan isolate. Chi VMV-GD could infect peppers, N.tobacco var. Samsun NN and Nicotiana tobacum by artificial inoculation indoor. The disease symptoms on pepper mainly exhibited irregular dark green mottle on new leaves, dark green part with bubble-like bulge, curled or wrinkled margin, and even smaller leaves, deformity, line leaf. The symptoms on N.tobacco var. Samsun NN and Nicotiana tobacum exhibited necrotic lesion.5.We collected 21 kinds of pepper varieties and used Chi VMV-GD as pathogen to compare different pepper varieties' resistance. The results show that the resistance of the 14 th pepper varieties was the best(disease index: 0), and then 13 th pepper varieties(disease index: 3.24). While the resistance of the Huifeng One was the worst(disease index :75.46).6. We collected 16 kinds of plant virus pesticides commonly used in our country agricultural production. The control effect on pepper virus disease was evaluated. The results showed that the control effect of Ningnanmycin was highest with 35.71%, and then Toxic Fluorine Phosphorus(30.36%) and Atailing(20.26%). The control effect of the rest 13 pesticides was below 20%. The results illustrated that these pesticides had a certain degree control effect on pepper virus diseases, but the overall control effect was low, the differences of control effect among the pesticides were also obtain.