Established in 1960 near Rome and supported by the US Atomic Energy Commission and the International Atomic Energy Agency, the Casaccia Center for Nuclear Studies played a fundamental role in transforming what became known as “mutation breeding” from an uncertain set of technologies into a robust area of research and development at both the national and international levels. At the time, there was a struggle for authority over plant breeding between the advocates of using nuclear energy and those advocating more cost-effective methods such as pedigree selection or hybridization. The Casaccia Center strategically implemented a research program based on two crucial elements: first, the use of the “gamma field,” a circular area with a retractable gamma-ray source in the middle, where growing plants could be exposed to chronic irradiation; and second, the launch of a broad mutation breeding program of durum wheat, typically used for pasta making. Drawing from a variety of archival sources, this article shows how both programs were instrumental in legitimizing and bolstering the use of the “peaceful atom” in agriculture on a national and global scale.