Evaluation of Theory for Identifying Populations for Genetic Improvement of Maize Hybrids

The ability to identify populations with the greatest chance for breeding success may increase the use of unadapted populations by concentration of resources on favorable germplasm. This study was conducted to evaluate the effectiveness of a method (estimates of ')for identifying maize (Zea mays L.) populations with the greatest number of dominant alleles at loci that are homozygous recessive in a single cross. This study also evaluates the effectiveness of a relationship estimator for detecting similarities between a population and the inbreds of a single cross. Estimates of and the relationship estimator were calculated by using donor populations of known composition and relationship to the recipient single cross. Six recipient single crosses were formed from the diallel cross of maize inbreds B73, B79, B77, and Mo17o Donor populations were composed of various proportions of inbreds B79 and B77. Estimates of correctly identified the population expected to have the largest number of unique dominant alleles in three of five single crosses (60%) for grain yield. for ear height, correctly identified the population expected to have the largest number of unique dominant alleles in four or five single crosses (80%). Estimates of did not identify populations expected to contain dominant alleles for earlier silking, suggesting that additive gene action or epistasis were important for siiking date. The relationship estimator for yield correctly identified the known relationship between the populations and the inbred parents of the single crosses. The successful application of to exotic populations is uncertain because of a low frequency of favorable dominant alleles contained by exotics for important economic traits. Joint contribution from the Field Crops Res. Unit, USDA-ARS, and Dep of Agronomy, Iowa State Univ.; Journal Paper no. J-14560 of the Iowa Agric. and Home Economics Exp. Stn. Project no. 2778. Part of a thesis submitted by D.G. Pfarr in partial fulfillment of the requirement for the M.S. degree.