They are sometimes referred to as “Texas Early Grano.”
Many subvarieties have been developed.
Grano Onions were developed from seed originally imported from Spain to Texas in 1925. The seed was called Valencia Grano 9452. Grano’s original disadvantage was that it was later to market than the Bermuda onion, by about two weeks. The Texas Agricultural Experiment Station began development of the variety in 1933. Through selected breeding, by 1940 they had developed a variety that matured up to two weeks earlier than Bermudas. They released this variety in 1942. The test field in which the successful strain was grown was field number 502, so the strain got informally called Texas Grano 502. Officially, the name is Texas Early Grano.
Grano onions are still grown on a small scale, but their greater claim to fame now is that they have been used to develop many subsequent sweet onion varieties.