To evaluate the approach, we cloned eight fragmentsfrom viruses PR8 and A/Chicken/Jiangsu/WS1/2012(H9N2) (WS1)respectively. All eight influenza genes from the cDNA of PR8 andWS1 were efficiently amplified by the fragment specific primersand had the expected molecular mass (Fig. 2). After the recom-bination of the PCR amplicon with the linear vector mediated byenzyme ExnaseTM II, the positive clones were screened by PCRand sequenced. During the screening of positive clones, we foundthat more than 90% of the selected clones were positive. Thispositive rate of clones was similar to that claimed by the Clon-ExpressTM II kit. Through this cloning strategy, we rapidly andefficiently got all positive clones for the eight influenza genesfrom the cDNA of PR8 and WS1 during a single ground of PCRand in vitro recombination. To further evaluate if the cloned genes