Morphological And RDNA Comparison Of Chinese Stem Nematode Population(Ditylenchus) Occurrence On Sweetpotato

Morphological and molecular identification for ten sweetpotato stem nematode populations collected from Beijng, Hebei, Shandong, Jiangsu, Anhui province in China were carried out in this study. The ITS regions of rDNA were sequenced and analyzed, and species specific primers were designed.Some important morphological characters were observed with both Light Microscope and Scanning Electron Microscope (SEM) and morphometrics were measured. It revealed that the sweetpotato stem nematode in China was identical to the Ditylenchus destructor.The amplification of the rDNA-ITS region from eight sweetpotato stem nematode populations of Daxing of the Beijjng city, Lulong, Funing, Yixian, Luanxian, Luannan of Hebei province, Pingyin of Shandong province and Sixian of Anhui province (codes Dd1-Dd8) in China and D. myceliophagus from UK yielded one single fragment of approximately 900bp, whereas the PCR product of ITS from two sweetpotato stem nematode populations Yishui of Shandong province and Tongshan of Jiangsu province (codes Dd9-Dd10) in China was about 1200bp. Restriction digestion of the ITS with 14 enzymes yielded identical restriction patterns for Ddl-Dd8. Restriction digestion patterns were identical to Dd9 and Dd10, but Dd9 and Dd10 could be distinguished by digestion of AluI and RsaI.The ITS products from sweetpotato stem nematode of China were sequenced and analyzed. ITS sequence of Ddl-Dd8 populations of sweetpotato stem nematode from China was 727bp, whereas the Dd9-Dd10 isolates was about 915bp. Sequence alignments of the ITS region of Dd1-Dd8 of sweetpotato stem nematodes from different area of China showed little variation, and the Dd9-Dd10 population presents mini-difference. It was found that there were clear sequence differences based on ITS1 region between Dd9 and DdlO, and the similarity was only 93.6%. This is the first report about the molecular data of D.destuctor from China, which show high similarity to that from England and U.S.A..Based on the ITS sequence, the species specific primers of sweetpotato stem nematode populations in China were designed. A method for rapid molecular diagnosis of sweetpotato stem nematode based on duplex PCR with species specific primer was described. 11 populations originating from China and UK were tested by duplex PCR. This is the first species specific primer of sweetpotato stem nematode in China.