Triangle of U

The triangle of U (/uː/ OO) is a theory about the evolution and relationships among the six most commonly known members of the plant genus Brassica.

[4] Woo made synthetic hybrids between the diploid and tetraploid species and examined how the chromosomes paired in the resulting triploids.

[2] The framework proposed by Woo, although backed by modern studies, leaves open questions about the time and place of hybridization and which species is the maternal or paternal parent.

The situation with B. napus (AACC) is more complex: some specimens have a rapa-like organellar genome, while the rest indicate an ancient, unidentified maternal plant.

[7][8] In 2011 and 2018, novel allohexaploids (AABBCC) located at the "center" of the triangle of U were created by different means,[9][10][11] for example by crossing B. rapa (AA) with B. carinata (BBCC), or B. nigra (BB) with B. napus (AACC), or B. oleracea (CC) with B. juncea (AABB), followed by chromosome duplication of the triploid (ABC) offspring to generate doubled haploid (AABBCC) offspring.

Triangle of U
The "triangle of U" diagram, showing the genetic relationships among six species of the genus Brassica . Chromosomes from each of the genomes A, B and C are represented by different colours.