In this recipe, can I substitute or do without the white wine? Is there a non-alcoholic substitute? 
Consider using white wine vinegar. The flavour profile obviously isn't the same, acetic acid changes things a lot, but you do get the other flavour compounds you get in wine.  That said, subjectively speaking, I agree with the suggestion of lemon juice to go with fennel and sour cream. Or maybe a combination of the two. 