This paper examines the link between passage of the Plant Variety Protection Act (PVPA), private R&D, public R&D, and genetic diversity in farmers' fields. PVPA did have a limited positive impact on private wheat breeding but did not lead to a decrease in public wheat research. Instead, public wheat research increased rapidly after PVPA passed. The trends in wheat diversity over time for the entire United States suggest that private research has undergone minor increases in diversity. Regression analysis of genetic diversity in Kansas, Nebraska, and Montana indicates that public sector research has increased diversity in farmers' wheat fields and that PVPA has had a small positive impact on diversity.