Brassicoraphanus

Brassicoraphanus is any intergeneric hybrid between the genera Brassica (cabbages, etc.) and Raphanus (radish). The name comes from the combination of the genus names. Both diploid hybrids and allopolyploid hybrids are known and share this name.

Early experimental crosses between species of these two genera had been sterile or nearly sterile, but large-scale experiments by Soviet agronomist Georgi Dmitrievich Karpechenko using Raphanus sativus and Brassica oleracea were remarkable because some of the plants produced hundreds of seeds. The second generation were allopolyploids, the result of gametes with doubled chromosome numbers.

• P0: Raphanus $2n_R=18$ x, a new crop in agriculture Brassica $2n_B=18$

• F1: sterile hybrid $n_R+n_B$
• Some of F1 spontaneously doubles their ploidy, resulting in the fertile allopolyploid $2n_R+2n_B$

File:Figure 2. Schematic representation of homoploid and allopolyploid hybrid speciation. Updated.svg

Hybrid speciation by spontaneous allopolyploidy.

As Karpechenko realized, this process had created a new species, and it could justifiably be called a new genus, and proposed the name Raphanobrassica for them, but the earlier name Brassicoraphanus has priority. Plants of this parentage are now known as radicole.

Karpechenko wanted a plant with leaves of a cabbage and the roots of a radish, but got the opposite. It is useful as fodder for livestocks, but not humans.

Two other fertile forms of Brassicoraphanus are known by the following informal names:

• The Raparadish group are allopolyploid hybrids between Raphanus sativus and Brassica rapa, used as fodder crops
• The Radicole group are allopolyploid hybrids between Raphanus sativus and Brassica oleracea, used as fodder crops
• Raphanofortii is the allopolyploid hybrid between Brassica tournefortii and Raphanus caudatus

Currently, it is thought that a great part of the flowering plants have some hybridization and polyploidization among their ancestors.

External links

• Observed Instances of Speciation