Preliminary Study On The Isolate CN-Huairou Of Prunus Necrotic Ringspot Virus And Risk Assessment Of Seedling By Simulating

Primus necrotic ringspot virus (PNRSV) is a quarantine virus issued in 1992 in China. The materials of cherry, apricot, peach, and plum leaves, sampled from Huairou, Pinggu were detected in bioassay, DAS-ELISA, and RT-PCR methods in this study. And one isolate of Prunus necrotic ringspot viru was found in cherry in Huairou.Sap extracted from infected cherry leaves was inoculated on the Cucumis sativus, and one isolate was separated, named CN-Huairou. The Capsaid protein gene of this isolate was cloned by RT-PCR and subcloned into the pMD18-T vector, which was transformed into the Escherichia coli (E.coli) DH5 α .The sequence of CN-Huairou obtained in this study was then compared with previously reported sequences of 47 other PNRSV isolates obtained from other areas, especially from China, in the world. All the isolates share the 89%¹00% amino acid identity and all the isolates from China share the 93%¹00% amino acid identity. CN-Huairou shares 100% amino acid identity with the isolate Ring17 in sour cherry from German and the isolate 4-8. The 12 isolates from China may be divided into 3 different groups, and CN-Huairou, CN-Changli belong to group â…¡(PV96), CN-Hangzhou, group â…¢ (PE5), and others, group â… (PV32). The clustering of the isolates does not correlate with host species or geographic origin of the isolates, which accord with the earlier reports.Based on the analysis of nucleotide acid sequence and amino acid sequence, the isolate CN-Huairou CP gene has a difference of 6 nucleotides between 118 and 125 nucleotides, namely, the amino acids between 39 and 42, and the difference may be a general distinguishing feature of Group â…  to â…¡, â…¢. Apart from the 5^th amino acid not attained, the amino acid of 62^nd, 81^st, and 126^th in CN-Huairou CP gene were same to the serotype CH9 mild pathotype.Based on the theory of Monte Carlo Modeling, the Pest Risk Analysis System (PRAS) was developed by Delphi 7.0. And this software may analyze the risk of the pest quantificationally through the steps of scenario analysis, math modeling, and randomizing modeling. The risk of seedling carring plant virus was modeled by PRAS. The result showed that the risk may be none when the infection ratio (IR) below 1% and the maximum amount of seedling (MS) introduced below 250, or 1R<=2% and MS<=100, or IR<=5% and MS<=50 in 10,000 times. The risk may be none also as the 1R<=0.4% and MS<=500 for the fruit seedlings, and as the IR<=1% and MS<=250 for the woody flower seedlings.