A feature of hybrids is that as well as the F1 generation outperforming its parents the F2 generation loses much of the hybrid advantage and shows great heterogeneity in phenotype, particularly in biomass and flowering time. Among the F2 plants are some that have a biomass and flowering time phenotype very similar to the F1 hybrids. We selected a number of these F1 like plants and using recurrent selection in the F3, F4 and F5 generations we produced a number of independent pure breeding lines with a biomass similar to the F1 plants and increased seed yield. We called these lines “hybrid mimics” because although they are not hybrids they resemble them in phenotypes such as biomass, flowering time and seed yield. Genomic analysis of these hybrid mimics shows them to be essentially homozygous but with genomic segments from both parents. This result indicates that the large biomass phenotype of hybrids does not require heterozygosity. The hybrid phenotype must be brought about by interactions between these genomic segments both genetic and epigenetic. Gene expression analysis indicates that in the hybrid mimic lines many genes show the same level of expression as in the F1 hybrids. Pathways for auxin and for cell expansion are upregulated in all the hybrid mimic lines and in the F1 hybrids providing a potential mechanism for the large phenotype.
Hybrid mimic technology may be applicable to crops and provide a method of achieving hybrid level yields without the costs of hybrid seed production. They may also allow crops in which there is no hybrid seed technology to gain the yield advantages of hybrids. These benefits may be important in developing countries where the cost of hybrid seed prevents its use.