Created in 1943, the Mexican Agricultural Program (MAP) was a collaborative program between the Rockefeller Foundation and the Mexican government aimed at improving yields of corn and wheat varieties in Mexico. The MAP's wheat program was more influential than its corn breeding program, and wheat became the centerpiece of the Green Revolution beginning in the 1960s. This article reveals that the environmental origins of the MAP's wheat program lay in combating a plant disease fungus commonly known as wheat rust, which harmed farmers in both northern Mexico and the US hard red spring wheat region. Rust outbreaks originated in US barberry bushes, so one might think that Mexican scientists would have entered the United States to solve this problem with transnational wheat rust. Instead, the reverse occurred. Nevertheless, the MAP successfully produced new rust-resistant wheat during the formative years of the MAP's wheat program. Between 1943 and 1953, rust-resistant wheat helped increase Mexican wheat production 84 percent and yields 59 percent. Rust-resistant wheat offered an alternative model for a sustainable, resource-neutral green revolution. Rather than remain in their field of expertise, plant pathologists pivoted to semidwarf wheat and fertilizer use after 1953, a shift that defined the course of the Green Revolution.