Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2009
Publication Date: 10/13/2009
Citation: Flint Garcia, S.A., Buckler IV, E.S., Tiffin, P., Ersoz, E., Springer, N.M. 2009. Heterosis is Prevalent for Multiple Traits in Diverse Maize Germplasm. PLoS One. 4:e7433. Interpretive Summary: The corn hybrids that farmers plant are the result of crossing two distinct inbred lines. Commercial corn breeding companies and public breeding programs spend vast amounts of time and resources testing corn inbreds and hybrids in order to identify promising new varieties. Models for predicting the performance of hybrids are needed to save time, money, and resources, thus improving the efficiency of breeding programs. However, accurate predictions are hindered by the phenomenon of hybrid vigor, or heterosis, where the hybrid outperforms the two inbred parents. In this study, we conducted experiments to determine whether any of three factors (inbred performance, genetic relatedness between the inbred parents, and/or differences in maturity between the target environment and the testing environment) could predict heterosis for a wide range of traits over a very broad set of germplasm. We found that these three factors varied in their ability to predict hybrid performance and heterosis for the traits we measured. Our results suggest that heterosis cannot be treated as a distinct trait in itself, and that heterosis may actually be controlled by partially separate mechanisms for different traits. Our findings are important to plant geneticists who investigate the mechanisms underlying heterosis, and to public and commercial breeders who test inbreds and hybrids to maximize corn productivity.
Technical Abstract: Heterosis describes the superior phenotypes observed in hybrids relative to their inbred parents. Maize is a model system for studying heterosis due to the high levels of yield heterosis and commercial use of hybrids. The inbred lines from an association mapping panel were crossed to a common inbred line, B73, to generate nearly 300 hybrid genotypes. Heterosis was evaluated for seventeen different phenotypic traits in multiple environments. The majority of traits exhibit better-parent heterosis in most of the hybrids studied. Heterosis levels often exhibit low levels of correlation for different traits suggesting that the various traits may have distinct mechanisms of heterosis. The ability to predict heterosis levels using inbred phenotype or genetic distance between the parents varied for the different traits. For some traits it is possible to explain a significant proportion of the heterosis variation using linear modeling while other traits are more difficult to predict. Together, these data provide evidence for the lack of a single underlying mechanism of heterosis.