Self pollinators: Pure line selection
The progeny of single plant selections are kept separate, not bulked together.
The expected result is a set of genetically homogeneous lines.
Selection is then imposed on rows (or plots) of the progeny.
This is the commonest approach taken to improving landraces. Pure lines perform more predictably than heterogeneous landraces, but are also more vulnerable to abrupt environmental changes (eg new race of a pathogen).