Desiccated samples of young canker and leaf tissue from affected lemon (Citrus x limon) and orange (Citrus x aurantium) trees, were returned to Australia and subject
ed to mandatory gamma irradiation at 25 KGy. Nucleic acids were extracted using a Qiagen DNeasy Plant Mini Kit and screened by PCR using the primer pair J-pth 1/J-pth 2 (Cubero and Graham 2002) following the protocol from the Australian draft national standard. A PCR product of the expected size (197 bp) was produced. In
confirmatory analyses in a second laboratory, this test was repeated successfully and a second assay, using the primer pair Xac01/Xac02 (Coletta-Filho et al. 2006), also gave a diagnostic fragment (581 bp). The amplified fragments from all three reactions (two J-pth 1/J-pth 2 productsand one Xac01/Xac02 product) were purified and subjectedto nucleotide sequence analysis, confirming that the bacterium was X.citri subsp. citri.