My wife is having recurring bouts of nausia and gagging. She also has developed a very poor appitite. What are the likely causes?

Unknown. Nausea and appetite go together. If she is nauseated, then she will likely have a poor appetite. For the gagging, this is somewhat more difficult. Does it occur when eating? Does it happen with both solids and liquids? Does she regurgitate any food? Is it partially digested or look untouched? These are best answered in front of your doctor. They can order the appropriate test or referral.