Question
could u plz tell me how to bet it ? thanks

Answer
I think you may mean clubroot.  It is a strange little organism that affects only certain plants roots and it lives in the soil .  Rotating away from that area to grow the susceptible plants is the easiest strategy.  They do sell fumigants such as Vapam and K-pam that can be bought and used, but their efficacy is in question.  I would move my garden area.  Good Luck.  Thanks.