Identification of useful tropical maize germplasms

The exploitation of the diverse forms of tropical maize (Zea mays L.) to broaden the germplasm base of U.S. maize has been hindered by problems of adaption and also by a paucity of information regarding the agronomic potential of the thousands of accessions of maize stored in germplasm banks. Studies were undertaken to identify tropical maize germplasm with potential to improve U.S. maize. Two studies were part of a long-term project to evaluate the typical Latin American racial collections via a multi-stage testing approach. Collections were evaluated in short-day environments in previous testing stages, so as to avoid confounding effects of photoperiod sensitivity. From an original set of more than 1300 accessions, 40 collections were chosen for evaluation for combining ability with U.S. germplasm in temperate environments. The chosen accessions were used to produce photoperiod-insensitive semi-exotic populations containing either 50%- or 75%-exotic germplasm. In the first study, 40 50%-exotic populations were evaluated in testcrosses to Reid Yellow Dent and Lancaster Sure Crop testers. In the second study, 19 75%-exotic populations representing the highest yielding accessions from the 50%-exotic experiment were evaluated in testcrosses to a Corn Belt tester. Testcrosses of many 50%- and 75%-exotic families were higher-yielding than B73Ht x Mo17Ht. A third study investigated the inheritance of resistance to southern corn rust (incited by Puccinia polysora) in two F...