Anil,
You have not stated whether the wife has any taxable source of income or not. Liability to pay income tax would depend on whether the wife has any taxable source of income individually or not. If the answer is in affirmative then the wife alone is responsible and liable to pay income tax on the net proceeds. If the answer is in negative then the income from net proceeds of sale of land of wife would be clubbed with the income of the husband and taxed accordangly.
It should be borne in mind that the amount mentioned in the sale deed would taken into consideration for arriving at tax liability.
if the wife is to be taxed then the cost of acquisition of land incurred by husband would be taken as cost of acquisition of land incurred by wife as on date of gift deed.