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ISRN Botany
Volume 2012 (2012), Article ID 682824, 12 pages
Review Article

Heterosis: Many Genes, Many Mechanisms—End the Search for an Undiscovered Unifying Theory

Department of Agronomy, University of Wisconsin, 1575 Linden Drive, Madison, WI 53706, USA

Received 24 September 2012; Accepted 11 October 2012

Academic Editors: H.-J. Huang, K.-B. Lim, and S. Schornack

Copyright © 2012 Shawn Kaeppler. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Heterosis is the increase in vigor that is observed in progenies of matings of diverse individuals from different species, isolated populations, or selected strains within species or populations. Heterosis has been of immense economic value in agriculture and has important implications regarding the fitness and fecundity of individuals in natural populations. Genetic models based on complementation of deleterious alleles, especially in the context of linkage and epistasis, are consistent with many observed manifestations of heterosis. The search for the genes and alleles that underlie heterosis, as well as for broader allele-independent, genomewide mechanisms, has encompassed many species and systems. Common themes across these studies indicate that sequence diversity is necessary but not sufficient to produce heterotic phenotypes, and that the molecular pathways that produce heterosis involve chromatin modification, transcriptional control, translation and protein processing, and interactions between and within developmental and biochemical pathways. Taken together, there are many and diverse molecular mechanisms that translate DNA into phenotype, and it is the combination of all these mechanisms across many genes that produce heterosis in complex traits.