H4 Visa No Surname in passport,Only Given Name is available

[splendor]

Hi,
I am applying for my wife's H4 visa,I am trying to fill DS-160 form.it is asking me to fill the surname.My wife's surname is blank in the passport.


Surname:..........
Given Name : Radha krishna **** **

Please let me know how to fill the first name and the surname fields in the DS-160 form.

Thanks in advance.

[immihelp]

Last Name = Radha krishna
First Name = FNU