Maize population hybrids : An exploitation of U.S. temperate public genetic diversity in reserve

Abstract

Public maize (Zea mays L.) breeding pro- grams provide genetic diversity in reserve through con- tinuous genetic improvement of elite genetically broad- based breeding populations. These elite populations have been moderately utilized as improved adapted sources of elite inbred lines for quantitative traits. The number of successful heterotic combinations currently available is limited because public genetic diversity in re- serve has not been fully exploited. Maize population hy- brids can exploit heterosis in a fashion similar to single- cross hybrids through a 'population-hybrid' concept. To date, heterotic patterns of population hybrids with rela- tively high mid-parent heterosis values have not been ex- ploited. In addition, few reciprocal recurrent selection programs have been developed and utilized for this pur- pose. Our purpose was to identify genetically broad- based U.S. temperate maize populations and population hybrids derived from breeding programs with continuous and extensive use of recurrent selection that may have an impact on public and private breeding programs. Elite maize population hybrids that averaged 28.2% high-par- ent heterosis was detected. Based on these data we be- lieve further efforts are needed to determine the practical use of genetically broad-based germplasm and whether these efforts justify the existence of public maize breed- ing programs. Re-direction of public breeding efforts may be needed.