You can execute a registered Gift(settlement) Deed in favour of your wife, conveying her undivided half joint share in your aparment. As per the laws prevailing In Andhra Pradesh, you will have to pay stamp duty to the extent of only one percent of Registrar's Office basis register value of the property which you intend to gift.,
It is not legally advisable and possible to execute a relinquishment deed for 50% of your Apartment, because your wife is not a joint owner(Co-ownera) of the said Apatment. A relinquishment deed can only be exeucted between joint owners of the property.
I differ to agree with the opinion of Sri.Ramesh Chedda, no body would express intention to benefit his wife, unless he has some love and affection towards her. In your case, your intention speaks volumes about your love and affection towards your wife. Further, you did not mention about your parents