|MadSci Network: Microbiology|
This is a good question. Most species of molds that will grow on bread will probably do well on any kind of bread. The factors necessary for this growth (nutrients, oxygen, water, and time) will be present in any bread. Some types of breads may have ingrediants with chemicals that could potentially inhibit mold growth. Most likely these chemicals would be food additives specifically added to prevent mold spoilage. For example, if you were to compare home-made white bread to a commercial white bread, the home-made bread would get moldier first because it does not contain the preservatives that most commercially produced breads do.
Molds are not "attracted" to foods. Filamentous fungi, or molds, reproduce by producing spores. These spores can travel through the air, like dust particles. When a spore lands in a favorable environment it will germinate and begin to produce mycelia, the fuzzy stuff that you have seen on moldy food. Mold spores are very common in the air and dust, so it is easy to contaminate food surfaces with these spores if they are left exposed to the open air. The types of mold that end up on the bread will depend on what type of spores are floating around in the bread's environment.
I hope that answers your question.
Try the links in the MadSci Library for more information on Microbiology.