ABSTRACT
The genus Allium offers excellent material for cytogenetical studies and for the applications of cytogenetics to crop improvement. Among the cultivated edible forms all have large chromosomes which are few in number and which can be readily and easily observed. The bulb onion is the most widely known edible Allium. It has been in use for at least 5000 years and there is an enormous reservoir of genetic diversity present in locally adapted forms grown in different parts of the world. The shallot is a form of Allium cepa that is propagated vegetatively by bulb multiplication, although some genotypes produce fertile flowers and set seed. In some parts of the world the shallot is still given the status of a separate species, but its flowers are typically those of Allium cepa and hybrids between the shallot and the bulb onion have a regular meiosis and are fully fertile.
