Identification of Agronomicaily Superior Latin American Maize Accessions via Multi‐Stage Evaluations

Few data exist regarding the agronomic utility of tens of thousands of available tropical maize ( Zea mays L.) racial accessions. A long‐term, multi‐stage evaluation project has been developed at North Carolina State University to evaluate the breeding potentials in the temperate USA of typical Latin American maize germplasm collections. Agronomic evaluations of accessions per se were performed in daylength neutral environments. Superior accessions were crossed to a temperate‐adapted inbred line and converted to photoperiod‐insensitive 50%‐exotic and 75%‐exotic populations by selection during 1986 to 1990. These semi‐exotic populations were evaluated as testcrosses to Corn Belt testers in North Carolina during 1993 and 1994. Testcrosses of many 75%‐exotic families were higher‐yielding than the hybrid tester, B73 Ht × Mo17 Ht , providing evidence that agronomically superior Latin American maize accessions possess favorable genes for yield that apparently are absent from Corn Belt germplasm. Yields of accessions evaluated as 100%‐exotic and 50%‐exotic populations were significantly correlated ( r = 0.62, P = 0.005) with each other, but not with yields of 75%‐exotic populations. Some accessions exhibited extreme ranking changes across different testing stages. Multi‐stage evaluations of maize racial accessions successfully identified superior germplasm for use by U.S. breeders, but there is no guarantee that all of the most valuable accessions were advanced to later testing stages. Evaluations in many environments and minimal culling levels at each stage could be used to improve the probabilities of successfully identifying useful accessions in future multi‐stage evaluation procedures.