IDENTIFICATION OF QUANTITATIVE TRAIT LOCI USING A SMALL SAMPLE OF TOPCROSSED AND F4 PROGENY FROM MAIZE

Plant breeders have an interest in the identification of genomic regions associated with the expression of quantitative traits because they recognize that such information could be used to improve realized heritability and reduce time per cycle of selection. The development of molecular marker technologies may provide tools to accomplish these goals. Maize (Zea mays L.) breeders develop new inbred parents of hybrids through topcrossed and per se evaluation of numerous quantitative traits in segregating progeny from planned breeding crosses. This study was conducted to determine if regions of the genome associated with variability of agronomically important traits could be identified by a small, but typical, sample of topcrossed and F-2:4 progeny from the cross B73xMO17. We identified genomic regions in 24 agronomic traits, using interval mapping and simultaneous estimation of multiple quantitative trait locus models. The estimated numbers of quantitative trait loci (QTL) identified per trait were about three to five. Many of the identified QTL were the same for correlated traits. Interestingly, yield QTL were not in the same regions previously reported for B73xMO17. This comparison contains a number of potential confounding factors: source of parental inbreds, type of progeny, different genotype x environment interaction effects, and different small samples of progeny from the cross. Consideration of these factors and the power of the tests to identify QTL suggests that the sampling of progeny is the most likely explanation for the differences.