Identification of tropical and temperate maize populations having favorable alleles for yield and other phenotypic traits

If tropical germplasm is to be useful in increasing maize (Zea mays L.) grain yield, populations containing Favorable alleles not present in elite hybrids need to be identified. Thus, a major objective of this study was to identify tropical and temperate populations containing favorable alleles useful for improving the Corn Belt hybrid FR1064 x LH185 (a commercial hybrid representative of the typical Stiff-Stalk x Lancaster heterotic pattern). A group of tropical populations and hybrids from the Germplasm Enhancement of Maize Project (GEM) crossed to either Mo17 or B73 (temperate maize inbreds) was studied. In addition, a group of temperate accessions was evaluated. Grain yield, flowering date, plant height, ear height, and penetrometer reading were evaluated using Dudley's method for identifying populations with favorable alleles. Only three accessions of 41 had positive and significant relative numbers of favorable alleles for yield. For most accessions, unexpectedly, the estimate of iota (p) over bar(l)mu' (an estimator of relative number of favorable alleles in the secessions not present in the hybrid to be improved) for yield was negative. Negative iota (p) over bar(l)mu' values for yield resulted from low true values of iota (p) over bar(l)mu' combined with low frequencies of favorable alleles in the accession for loci having favorable alleles in one inbred and not the other. None of the accessions were identified as having favorable alleles for lowering ear height or increasing stalk penetrometer resistance. These results suggest Dudley's method may not be useful when frequencies of favorable alleles in the populations being evaluated are very low.