| Virus diseases are the second major categories diseases on crops, so it is difficult to control. Chemical control is one of the important measures to prevent crop virus diseases.Since virus inhibitors differentiate in prevention impact and action mechanism and the control effect of virus inhibitors may differ in different regions, it is very important to conduct field test before promoting large area popularization of pesticides. Test in large area on virus inhibitor effect needs huge workload. Traditional method needs virus inoculation in local infection virus host and consumes more time. Could it be possible to develop a method for quick identification of virus inhibitors control effect? This is a good question to be investigated. In addition, variation of plant viruses occurs frequently in nature. Will continuous use of one single virus inhibitor lead to mutation in virus genome so as to avoid or defend the inhibitor stress? All the questions above were investigated in this study.0.5%oligosaccharide agent,24%mixed fatty bluestone 20%hydroxyzine cupric acetate wettable, which are recommended as plant virus inhibitors by in China National Tobacco Corporation, were selected for the analysis of prevention and control effect in a tobacco-plant area, Chenzhou, Hunan. Results showed the average prevention effects of 0.5%oligosaccharide agent and 24%mixed fatty bluestone on tobacco mosaic disease were 81.12% and 81.13%, respectively, and the average control effects were 62.08% and 71.74%, respectively. The average prevention effect of 20%hydroxyzine cupric acetate wettable was 56.14% and the average control effect was 19.66%. So 0.5%oligosaccharide agent and 24%mixed fatty bluestone are suggested to be used in fields alternatively.In order to screen out virus inhibitor and evaluate the control effects, we use PVX-GFP infectious clone infect tobacco, with 0.5% oligosaccharide agent treat on the leaves. The movement of PVX-GFP in the leaf was surveyed by UV light on 2 days after infection. Pictures were collected and the dimension of fluorescence spots were measured. And mechanical inoculation method was also used for comparison. The results showed the diameter of fluorescence spots in the treated leaf were smaller than those of the untreated leaf. Our result offers an idea about the establishment of a quick evaluation system of virus inhibitor.Lentinan and Dufulin are two plant virus inhibitors. Lentinan inhibit the production and replication of virus. Dufulin enhance immunity of crops to prevent virus spread. We inoculated the healthy tobacco by the method of mechanical inoculation, then continuously treat the infected leaves eight times in eight months with Lentinan and Dufulin, respetively. Specific primers for RdRp and CP region of PVX were designed for the amplification by RT-PCR. The RdRp and CP of PVX from the leaves treated in 3th,5th and 8th times were cloned, sequenced, and were compared with the initial sequence of PVX. The results showed that there was no obvious nucleotide and amino acid mutation in the CP region of PVX from the leaves treated by both of the virus inhibitors for 8 times. Compared to that of the control, there was only one amino acid mutation in the RdRp region of PVX from the leaves treated by both of the virus inhibitors for 8 times, and the mutation loci was different.This study screen out two plant virus inhibitors,0.5%oligosaccharide agent and 24%mixed fatty bluestone, which have better prevention and control effect for Chenzhou tobacco-planting area. A quick evaluation system was tried to set up in labotory and it provides new ideas for quickly screening and evaluation of crop virus inhibitors. Lentinan and Dufulin were used to treat the PVX infected tabacco for 8 times during 8 months and the variation of PVX RdRp and CP region were analyzed. Finally, the reasons that caused the results were discussed. |
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