Fig. 1

HA RT-PCR product. a Schematically, the designed primer sets generate overlapping fragments (blue bars) to obtain the full length of HA gene (red bars). Black bars represent the untranslated region (UTR). The black arrows represent the inner primers for sequencing to obtain complete coding sequences. b The HA1 and HA2 fragments were approximately 900 bp in length. NC represents negative control. Line 1, 2, and 3 represent the annealing temperatures of 50, 55 and 60 °C, respectively. M represents DNA Marker with size increment of 100 bp