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. 2001 Oct;75(20):9679–9686. doi: 10.1128/JVI.75.20.9679-9686.2001

FIG. 1.

FIG. 1

Phylogenetic tree for the H9 HA1 gene of influenza A viruses. The nucleotide sequences of the HA1 gene (960 bp from position 55 to 1014) were analyzed with the Phylogenetic Analysis Using Parsimony program using a maximum-parsimony algorithm. The HA1 phylogenetic tree is rooted to A/Dk/Alberta/60/76 (H12N5). The lengths of the horizontal lines are proportional to the minimum number of nucleotide differences required to join nodes. Vertical lines are for spacing branches and labels. The bootstrap value (∗) for 1,000 replications was computed using MEGA software (version 1.0; Pennsylvania State University, University Park), and the results for key branches in the tree are depicted. Abbreviations used in virus designations not used in the text are as follows: Gs, goose; Pg, pigeon; Ph, pheasant; SCk, silkie chicken; Ty, turkey; Kor, Korea; CA, California; WI, Wisconsin; AR, Arkansas; MN, Minnesota. Viruses isolated in this study are underlined. Group I, Qa/HK/G1/97 (H9N2) lineage; group II, Dk/HK/Y280//97 (H9N2) lineage; group III, Ck/Kor/006/96 (H9N2) lineage.