Abstract
Ts mutants in src from the Prague and Schmidt-Ruppin strains of Rous sarcoma virus (RSV) were used to superinfect chicken and quail cells chronically infected with the Bryan strain of RSV. No wild-type recombinants and few double-defective virions were produced. These results indicate that genetic recombination does not occur with high frequency in these heterologous crosses even if all infectious virus is derived from doubly infected cells.