Inbreed lines in maize are maintained by

Inbred maize lines are maintained by Self-pollination.
Inbred lines have been a rich resource for fundamental and applied investigations in maize. They constitute a sampling of the genetic diversity in Zea mays L. that has been captured and partitioned into an array of uniform, reproducible genotypes.
The nucleus seed of inbred lines can be maintained by self-pollination, sib-pollination, or a combination of the two procedures.