An immuno-capture polymerase chain reaction (IC-PCR) method for detection of Acidovorax avenae subsp. citrulli (AAC), the causal organism of bacterial fruit blotch (BFB) of watermelon, was developed by combining the immunosorbent enrichment (ISE) method with classical PCR and comparing with the direct PCR and growth check methods. The results showed that all A. avenae subsp. citrulli strains tested have produced 360 bp specific fragments using IC-PCR and direct PCR methods, while other strains from 10 different genera showed negative PCR results. The minimum detection concentration was about 50–100 cfu/ml and 104 cfu/ml, respectively. The IC-PCR sensitivity was 100 times higher than that of direct PCR. The examination of seven batches of different melon seeds from the markets by IC-PCR showed that one cantaloupe, two honeydew melon and two watermelon seed varieties carried the pathogen, indicating that the IC-PCR is an accurate, sensitive, rapid and low-cost technique.

Avian influenza virus is acquiring the ability to cross the species barrier between birds and mammals. However, the genetic mechanism of this ability is not well known. We successfully rescued an influenza A virus A/Chicken/Guangdong/03 (H5N1), which is highly pathogenic to both SPF chickens and BALB/c mice, by plasmid-based reverse genetics. The rescued virus, R-A/Chicken/Guangdong/03 (R-CG), and the wild-type A/Chicken/Guangdong/03 (W-CG) were found to share similar biological properties, such as in titres of 50% egg infectious dose (EID50), 50% tissue culture infectious dose (TCID50) and intravenous pathogenicity index (IPVI). R-CG, like W-CG, is highly pathogenic in mice following natural route infection. Both R-CG and W-CG viruses can be isolated from many organs of mice such as brain, lung, kidney and spleen. As a result, the constructed R-CG reverse genetic system can be used as a tool in the investigation of the molecular mechanism of infection of the mammalian host by avian influenza virus.