(a) PCR amplification of the fp25k gene region (1 kb) from passaged WT and Ac-FPm virus (mixed population from passages 12, 15 and 21), indicating no insertion in the fp25k gene. (b) PCR amplification of the fp25k gene plus fp25k promoter region (1.54 kb) from 34 isolates of WT AcMNPV (individual plaques) at passage 12 showing no insertion in the fp25k gene; 33/34 of the WT virus isolates retained the complete fp25k gene. L, 1 kb size ladder; ML, molecular mass ladder; M, PCR with no DNA; W at passage 1, WT AcMNPV at passage 1; m0, Ac-FPm0; I, isolate; Δ, Δfp25k AcMNPV.