How do hybrid species form?

Annaliese Mason, Plant Breeding Department, Justus Liebig University Gießen

Hybridization (where two species come together to form a new species) has played a major role in evolution and speciation, particularly in the flowering plants. Many crops grown today are hybrid species, including wheat, canola, sugarcane and cotton. However, exactly how hybrid species form is still a complete mystery in almost all genera. New hybrids face a number of challenges to establishment, the most serious of which may be regulating meiosis. In most newly-formed hybrids, two sets of chromosomes from each of the progenitor species will be present. These sets of chromosomes not only contain competing genomic information, but almost always share regions of genomic similarity that can confuse the meiotic cell machinery. Failure of meiosis to correctly segregate chromosomes belonging to different genomes usually results in sterility in the hybrid, and loss of chromosomes and genomic information from one generation to the next. Hence, hybrids must regulate meiosis to establish. But how? In the Brassica genus (cabbages, turnips, canola, mustards), species share combinations of the A, B, and C genomes: A, B, C, AB, AC and BC genome-types all exist as established crops. Via production and investigation of Brassica hybrids of different types with different genome combinations, our research aims to answer the question of how hybrid species form, and to potentially build new crop species through novel interspecific hybridization events.

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