Abstract: The frequency of lysogenic cell (FLC) is an important index representing viral ecological function. To explore a suitable method for freshwater FLC test, water samples from six freshwater lakes were collected and treated with different induction methods, including direct induction, induction combining filtration, induction combining filtration and oscillation, direct induction combining oscillation. The FLC was calculated from the induced host mortality. The results showed that the FLC under the directinduction method was significantly higher than those under other methods for both phytoplankton and bacterioplankton (P<0.05), indicating that the lytic infection under the direct i〖HJ*5〗nduction had a significant effect on the FLC test. Thus, the direct induction method is not suitable for assessing freshwater samples. There was no significant difference in the results from other methods (P>0.05), suggesting that the oscillation method can be as efficient as filtration in inhibiting lytic infection. Furthermore, the oscillation method is more convenient than filtration. In conclusion, the direct induction combining oscillation method is a simple and efficient way to test the FLC in freshwater.

Key words: phytoplankton, bacterioplankton, virioplankton, lysogeny induction.