Detection of quantitative trait loci for grain yield and yield components in maize across generations in stress and nonstress environments

Grain yield is the primary trait of interest in maize (Zea mays L.) breeding programs, but its evaluation is complicated by genetic heterogeneity, a complex biological basis, and genotype x environ ment interactions. Genetic mapping studies of grain yield and yield components, with common sets of DNA marker loci and different populations evaluated across a range of environments, might identify regions of the genome associated with more or less consistent effects in different genetic and environmental contexts. Our objective was to evaluate the consistency of quantitative trait loci (QTL) detection for grain yield and four yield components in maize across stress and nonstress environments. One hundred eighty-five F-6:7 lines from a cross between inbred lines Mo17 and H99 were evaluated in two climatically diverse years at the same location. The stress environment was characterized by cool, wet conditions and a 56% reduction in grain yield relative to the nonstress environment. Over all five traits, 59 QTL were detected in at least one of the two environments with 10 being detected in both environments. Thirty-two (54%) of the QTL were detected in the mean environment, and an additional eight QTL were detected in the mean that were not detected in either of the individual environments. Comparison of the Fb:7 mean environment QTL with the mean environment (same location, different years) results from the F-2:3 generation of the same population revealed 13 of 40 QTL detected in the F-2:3 were verified in the F-6:7 generation. Little evidence of cross-over type QTL interactions was observed, and QTL x environment interactions seem to be in the form of change in magnitude of effects.