Fig. 4.

Phylogenetic analysis of putative recombinant breakpoint located at position 700 of Spanish 4791 cluster 2 isolates. All twenty-six Spanish IBV field isolates were included in the comparison. Trees were generated by the Maximum Parsimony method with 1000 bootstraps in the Mega 3 package. 4a. Phylogenetic tree obtained when the S1 region from nt 1 to 700 in the alignment was used. Spanish 4/91 cluster 2 isolates (in bold letters) were grouped with the remaining Spanish 4/91 isolates. 4b. Phylogenetic tree obtained when the S1 region from nt 700 to 1623 in the alignment was used. Spanish 4/91 cluster 2 isolates (in bold letters) were clustered in an own phylogenetic branch closely related with Spanish Italy 02 isolates.