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How did bread wheat develop through hybridization and chromosome doubling?

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A large red and yellow combine harvester cuts through a golden wheat field, leaving neat rows of harvested grain behind. — Cereal farming Combine harvesting wheat.

Bread wheat (Triticum aestivum) developed through a series of natural, spontaneous hybridizations and subsequent chromosome doubling, a process known as polyploidy.12

When two closely related species cross-pollinate, the resulting hybrid is typically sterile because its chromosomes lack the necessary homologous partners required for successful meiosis. However, if the number of chromosome sets in the hybrid accidentally doubles, each chromosome gains a pairing partner, restoring fertility and creating a new, distinct species.132

Bread wheat is hexaploid (6n), meaning it possesses six sets of chromosomes. This state was achieved through multiple ancestral polyploidization events involving the union of wild grasses. This mechanism of speciation is a significant driver of evolution in plants, allowing for the development of complex, fertile organisms from the fusion of different ancestral genomes. While modern plant breeders can induce this process using chemicals like colchicine, the evolution of bread wheat occurred through natural, spontaneous events over time.123