Abstract: The objectives of the present study were to analyze sequence variations in the cytochrome c oxidase subunit 1 (cox1) gene among Ascaridia galli isolates from different provinces in China,and to study its phylogenetic relationships with roundworms of the other families using cox1 gene sequence. The partial cox1 (pcox1) were amplified from each A.galli sample,and pcox1 sequences were aligned using the Clustal X 1.81. MP and NJ trees were constructed using the software Phylip 3.67 version 4.0 and Mega version 4.0,and ML tree was also constructed using Puzzle version 5.2. The lengths of all the pcox1 sequences were 250 bp. Phylogenetic analyses showed that the eight isolates were clustered in the same clade. Sequence variations in pcox1 sequences within A.galli were 0 to 2.5% which was significantly lower than inter-species differences (6.9% to 15.3%). It is concluded that pcox1 sequences can be used as genetic marker for population genetic studies of A.galli. The results of this study provided foundation for further studies on molecular genetics and diagnostics of A.galli.

Key words: Ascaridia galli; mitochondrial DNA; cox1 gene; phylogenetic relationship