can I substitute Greek yogurt for sour cream in breads ?
are pretty similar in my opinion. I would give it a try!
If the sour cream is acting as all the fat in a recipe that needs fat to develop the proper texture (some bundt cakes and breads,for example) then you cannot substitute the fat free or low fat yogurt-you need another fat (butter or oil or lard).You might be able to substitute a full fat yogurt but the texture of the final product will still suffer.
If the sourcream is only for taste or moisture, then you probably can sub greek yogurt-even non fat or low fat.
If it is for a yeasted bread, substitute away-they are more forgiving. It will be a dryer crumb.
What makes "Greek yoghurt" different is its lower water content. I once substituted Greek yoghurt for buttermilk in a pancake recipe that said you could substitute yoghurt. I found the batter significantly dry and had to add water to obtain the right consistency. Keep this in mind.
My wife has substituted yoghurt for sourcream in a sourcream coffee cake for years with good results. Of course, this has additional sources of fat in the recipe. She uses "low fat," not fat free yoghurt.