Interception of Phytophthora syringae on Citrus fruits imported from California, USA
进境美国加州脐橙中丁香疫霉Phytophthora syringae的截获

Several brown rot fruits have been found from Californian fresh orange sample. Three isolates similar to Phytophthora syringae were obtained from these rot fruits. The colonies grew slowly on PDA and V8 juice agar (V8A). They were stellate, tiled and thin on V8A, but on PDA, the margin was chrysanthemum petaloid; mycelia dense, milk-white-colored. Sporangia and catenulate hyphal swellings formed in sterilizing water and soil extract water in 48h. The isolates were homothallic. Oospores were produced abundantly on PDA and V8A mixed with fresh Citrus fruit tissue or leaf of rhododendron. The isolates were wounded-inoculated on fresh Citrus fruits. Typical brown rot symptoms are apparent on inoculated fruits in 7d. DNA of hyphae was amplified with ITS1/ITS4 primers. In comparision with P. syringae from NCBI GenBank databases, the sequences had 99% identity. All the results of tests showed that the isolates were Phytophthora syringae.