While Hanna's research encompassed the breeding and production of tomatoes and asparagus as well as variety adoption studies with cabbage, broccoli, and sweet potatoes, the legacy of this much celebrated Davis alum and staff member is his cultivar VF145, the world's first mechanical harvesting tomato. When he first began trying to breed such a tomato in 1942, Hanna kept his idea to himself, unsure of what others at the university would think of it. Perhaps for good reason: when his concept started to circulate, it was met with little support, in terms of both its technical feasibility and its anticipated negative impact on California agricultural labor.
Hanna persisted in his vision, however, and after 20 years had developed what would become known as the "square tomato," a fruit firm and strong enough to withstand mechanical harvesting. With his cultivar in hand in 1961, he began collaborating with UCD agricultural engineer Coby Lorenzen, who designed the first mechanical harvester. By 1964, when the Bracero program, which had provided the United States with affordable agricultural labor from Mexico for over 20 years, was terminated, Hanna's tomato and Levenson's harvester were poised to save the state's $3 billion/year tomato industry. Though the unveiling of their mechanized system was not without heated controversy, the state's tomato acreage planted to mechanical harvesting tomatoes grew from 7% to 85% in just three years; and the industry bears Hanna's influence to this day.