Mitosis instead of Meiosis
In a new study, led by Charles Underwood from the Max Planck Institute for Plant Breeding Research in Cologne, Germany, scientists established a system to generate clonal sex cells in tomato plants and used them to design the genomes of offspring. The fertilization of a clonal egg from one parent by a clonal sperm from another parent led to plants containing the complete genetic information of both parents.
Tomato fruits produced by a tetraploid tomato plant (with 48 chromosomes) produced by crossing two different tomato MiMe parents.
Hybrid seeds, combining two different parent lines with specific favorable traits, are popular in agriculture as they give rise to robust crops with enhanced productivity, and have been utilized by farmers for over a hundred years. The increased performance of hybrids is generally known as hybrid vigour, or heterosis, and has been observed in many different plant (and animal) species. However, the heterosis effect no longer persists in the subsequent generations of these hybrids due to the segregation of genetic information. Thus, new hybrid seeds need to be produced every year, a labor-intensive and expensive endeavor that doesn't work well for every crop. So, how can the beneficial traits, encoded in the genes of hybrid plants, be transferred to the next generation?
Typically, our genetic material undergoes reshuffling during meiosis – a crucial cell division occurring in all sexually reproducing organisms. This reshuffling, due to random segregation of chromosomes and meiotic recombination, is important in generating novel and beneficial genetic configurations in natural populations and during breeding. However, when it comes to plant breeding, once you have a great combination you want to keep it and not lose it by reshuffling the genes again. Having a system that bypasses meiosis and would result in sex cells (egg and sperm) that are genetically identical to the parents could have several applications.
