Abstract:

A new canker disease had taken place on walnut (Juglans nigra) in Xinjiang. In resent years, it has caused severe damage to the walnut product. In this paper samples were collected from diseased walnut in walnut gardens and 2 isolates were obtained. The isolates were inoculated with both wound and healthy inoculation methods. Re-isolation from lesions formed by the inoculation was the same as the inoculatied isolate, demonstrating that the isolate was a pathogenic strain of Pythium oligandrum based on its morphology. The sequences of the isolates Pythium oligandrum were amplified by PCR technique with universal primers of fungi, and the sequences were further compared with that in GenBank. The molecular identification confirmed the results from morphology identification. This is the first report that Pythium oligandrum is the pathogen of walnut black water disease in China.

Key words: walnut black water disease, pathogenicity, morphological, molecular identification, Pythium oligandrum