Hybridization of the PBCV-1 dut gene to DNAs isolated from the host Chlorella NC64A, 42 NC64A viruses, and 5 Pbi viruses (CVA-1, CVB-1, CVG-1, CVM-1, and CVR-1). The DNAs were hybridized with a 32P-labeled a551l gene probe. The blots in each row contain 1, 0.5, 0.25, and 0.12 μg of DNA from left to right, respectively.